manipulating map objects -...

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Manipulatingmap objects

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6Understanding MapInfo: A Structured Guide

Ian Johnson 1996. Archaeology (P&H), University of Sydney

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DRAWING NEW OBJECTS

The Drawing toolbar contains a number of standard drawing tools which can be used both fordrawing objects with the mouse and for digitising objects with a digitising tablet (see chapter 9).Objects are inserted into the current editable layer on a map window. Drawing tools operate bothon map windows and on layout windows.

The drawing tools are available when a layout window is active or when a map window with aneditable layer is active. If a map window with no editable layer is active, the drawing tools willbe greyed out.

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The tools available are:

Symbol tool. Click on map to draw point objects in the current symbol style.

Line tool. Draws individual straight lines in the current line style. Press, drag andrelease to draw line in current line style. Shift to constrain at 0º, 45º, 90º. Ctrlextends line in opposite direction simultaneously.

Polyline tool. Draws open polylines (lines composed of multiple straight segments)in current line style. Click for individual nodes. Terminate line by double clicking.Shift constrains to 0º, 45º, 90º line segments.

Polygon tool. Draws closed polygons in current region style. Click for individualnodes. Automatic closure if node is within snap distance (page 125) of startingpoint, or close polygon by double clicking (mouse) or closure button (digitiser -pages 213, 217). Shift constrains to 0º, 45º, 90º line segments.

Arc tool. Press and drag out to desired arc size and shape. Shift constrains to arcof circle. Ctrl centres arc on starting point.

Circle/ellipse tool. Press and drag out to desired radius/shape. Shift constrains tocircle. Normally centred on start point. Ctrl constrains tangential to start point.

Rectangle tools (sharp and rounded corners). Press and drag out to desired sizeand shape. Shift constrains to square. Ctrl centres on starting point (reverse effectto circle/ellipse tool).

Text tool. Click position to enter text - brings up text insertion bar and inserts texttyped in current text style. Text can be several lines separated by Enter. Clickelsewhere, select another tool or press Escape to complete text. Double click textwith Select tool to edit text or modify style.




6Manipulating map objects

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Drag and drop tool. Use this tool to drag a map window onto the MapInfodesktop (to clone the map window) or into an OLE container application (page115).

Autoscrolling

When you are drawing on a map or layout window with a drawing tool and you move thepointer beyond the edge of the window, the map or layout will scroll in that direction, allowingyou to draw beyond the limits of the original window. You can stop scrolling by pressingEscape - the tool remains active.

? Autoscrolling only operates with tools which can be dragged. Single click tools, such as Info orSymbol, do not support autoscrolling.

Adding tabular data

Tabular data can be added to newly drawn objects on a map in one of two ways:

Click on an object with the Info tool and enter data into the Info toolwindow (page 152);

Highlight (select) the object(s) using any of the normal selection methods(page 86) and open a new browser window for the Selection table. Enter datainto the browser (page 153).

h Newly drawn objects can be automatically associated with an existing record in the tabular databy first selecting the record in a browser then drawing the object. New (blank) records can beadded to the browser/table with Edit>New Row (Ctrl-E).





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MODIFYING EXISTING OBJECTS

The map object(s) to be modified must be in the editable layer. The editable layer is indicatedin the status bar at the bottom of the screen.1

Select the object(s) by any appropriate method (selection on the map - pages 86 - 88; selectionon a browser - page 88; selection through queries - pages 89 - 91). 'Handles' will appear at thecorners of the bounding rectangle for lines, areas and text, one handle will appear at the centreof point symbols, and an additional handle (used for rotation) appears on text objects.

If the handles don't appear, the layer is not editable or there is a selectable layer above theeditable one and objects have been selected from this instead (objects can only be selected fromone layer at a time)

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Undoing edits

The last editing action (delete, move, copy, resize etc.) on a map window (or browser) can beundone by Edit>Undo (Ctrl-Z). Undo is limited to the last action and to a limited number ofobjects/records (maximum 800, default 10, set under Options>Preferences>System Settings).

Beware: If the number of objects/records modified exceeds the number set, NONE of thechanges are undone.

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Deletion

To delete the selected object(s), press the Delete key or Edit>Clear.

This deletes both the map object and the tabular data

If you delete the current selection in a browser, using Edit>Clear or the Delete key, theassociated map objects are also deleted, because they cannot exist without tabular data. Objectsand their associated tabular data can be deleted to the clipboard with Edit>Cut (Ctrl-X) - seedetailed discussion on pages 113 - 114.

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Edit>Clear Map Objects Only deletes only the selected map objects, but leaves the tabulardata unaffected.2




61 The status bar can be switched on and off with Options>Hide/Show Status bar.

2 You might use this prior to using Table>Create Points to ensure that new map objects are created from the X,Y valuesin the tabular data (which might have been modified), otherwise new map objects will not be created for tabular recordsfor which a map object already exists (page 64).

Manipulating map objects

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Duplication

h To duplicate the selected object(s), use Edit>Copy (Ctrl-C) then Edit>Paste (Ctrl-V). Thiscreates duplicate object(s) at the same location as the original(s). Point at one of these objects,press and drag the duplicate(s) to the location required. Where multiple objects are copied andpasted, dragging any one of the pasted objects, as long as they are still selected, will drag therest of them the same amount (see "Moving" below). Cutting, copying and pasting are discussedon page 113 - 114.

Moving

Note: There is a one second delay after the mouse button is pressed before the object(s) can bedragged. This delay exists to avoid inadvertent moving of objects when the mouse is clicked toselect an object and moved at the same time.

Single object

To move a selected object, point at any part of the object with the Select tool , press, dragand release. If the object is a polyline or text, the pointer must be on part of the line or on acharacter, otherwise the object will be deselected instead. The window will autoscroll (page 109)if the pointer moves off the edge of the window.

Multiple objects

When multiple objects are selected (page 86), point at any one of the objects and drag it. Allobjects are moved by the same amount. This is true whether or not all the selected objects arevisible on the screen.

h This is particularly useful for labelling e.g. large numbers of point objects, grid lines or mapoutlines. Having autolabelled the objects using the tabular data (e.g. with site name or identifier,grid latitude, map number etc.), one can zoom in on a small area for precise positioning oflettering relative to the objects and know that all the other labels selected will have been movedby the same amount.

! Beware: moving a line or area object outside the defined coordinate limits of a non-earthprojection will cause the part moved outside the defined limits to be truncated unpredictably.Moving a line or area object back into the mapped area will not reinstate the truncated section.

? Point objects moved outside the coordinate limits will 'stick' at the edges of the defined area(they will appear to move past the edges, but once the mouse is released they will jump back tothe nearest edge).

? Text objects behave in a rather more complicated manner: their centroid 'sticks' at the edge ofthe defined area, but the actual text can extend beyond the limits in some circumstances. Ifmoved off the bottom or top they are rescaled. If moved back into the defined area, anytruncated text is reinstated, but the scaling remains.





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Rescaling

To rescale (enlarge, reduce or change the overall shape of) selected line and area objects, use theSelect tool to drag the handles at the corners. When multiple objects are selected, dragging thehandle on any of the objects will rescale all the objects and the space between them. The handlecan be dragged more in one direction than the other to change the shape of the objects (e.g.squares into rectangles).

Hold down Shift to rescale in proportion (i.e. to maintain the same overall shape). Hold downCtrl to rescale around the centroid (normal rescaling expands or contracts the object(s) in thedirection of the handle which is dragged). Shift and Ctrl can be held down together to getproportional scaling around the centroid.

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Point objects (symbols) and text objects cannot be rescaled - their size is modified using the stylesettings (page 117). However the space between them can be scaled if the selection includes aline or area object whose handles can be dragged.

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Autotracing

When drawing or digitising3 contiguous polygons (such as a soil map or cadastral plan) theboundary between two polygons must be duplicated. If it is traced twice (once for eachpolygon) there will be overlaps and/or gaps between the two boundaries (page 218). This is bothmessy and can result in errors such as the attribution of a point to two polygons or to nopolygon at all if it falls in an overlap or a gap respectively. MapInfo's Autotrace function is oneway of avoiding manual retracing of boundaries and ensuring that duplicated boundaries areidentical.

To use Autotrace, you must be in snap mode (page 125) - turn on/off by pressing S. Draw ordigitise as normal until you reach the first node of the section of boundary which you wish totrace. Switch on snap mode if it isn't already on. Click to place a node in your new objectcoincident with the starting point of the section to be traced, then hold down the Shift key andpoint to the last node in the section to be traced. The straight line between the last node and thepointer will disappear and the path between the two, along the object, will be marked. Click onthe last node while continuing to hold down Shift to include the marked section in your newobject. Continue drawing or digitising until the new object is complete. You can include morethan one traced section in an object.

The first and last nodes in the section to be traced must be part of the same object, otherwisethe autotrace function has no effect and a straight line is drawn between the nodes. HoweverAutotrace will trace objects in any layer, not just the one you are editing.

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Normally MapInfo traces the shortest path along the object between the two nodes. If you holddown Ctrl rather than Shift when tracing a polygon, MapInfo will trace the longer path.




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3 Digitising (chapter 9) is precisely equivalent to drawing with a mouse, except that the position of the digitiser puck isconverted to coordinates relating to the paper map or aerial photograph (and thereby to the real world), rather than to thearbitrary space of the computer screen.


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CUTTING AND PASTING

Both tabular data and map data can be copied, cut and pasted with the usual Windowscommands (Ctrl-C, Ctrl-X and Ctrl-V), either within MapInfo or between MapInfo and otherapplications.

Cut and paste within MapInfo

Within MapInfo, map objects are cut and pasted as map objects to the same geographic locationin whatever layer is currently editable (not necessarily the same layer as the one from which theobjects were cut or copied). Map objects are pasted as new objects and will not replace ahighlighted selection.

When a map object is cut and pasted into a map window, the associated tabular data is alsopasted into the tabular data for the editable layer, creating new records. If data is cut from abrowser and pasted into a map window, both the map object and tabular data are pasted.

! When rows are cut from a browser, the corresponding map objects are cut from the table, eventhough the layer may not be editable on any open map window.

! If data is pasted into a browser, the map objects are not pasted into the table.

When tabular data is pasted into a different table and the table structures are different, theresults are unpredictable (MapInfo matches fields by order and type, so fields may not be pastedif the fields in the recipient table do not match up). No tabular data is pasted when map objectsare pasted to the cosmetic layer.

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? Since cut and paste always transfer tabular data (other than when pasting map objects to thecosmetic layer), it is not possible to paste into a read-only table (such as a table based on aspreadsheet or ASCII delimited file, or one locked by another application).

When a group of nodes are selected (by selecting them in reshape mode - page 123) and thencut or copied, they will be pasted as a polyline. When a single node is pasted, it will be pastedas a point object.

Copy and paste map window

When a map window is active and no objects are selected, Edit>Copy is modified to readEdit>Copy Map Window. When a map window has been copied to the clipboard, Edit>Pasteis modified to Edit>Paste Map Window.

Pasting a map window creates a new map window, equivalent to Map>Clone View or draggingthe map window onto the MapInfo desktop with the drag and drop tool. One use for this is tocreate a second view of the same data which can be zoomed in to create a pull-out from a smallarea.





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Moving objects within/between layers

Where several objects in the editable layer lie on top of one another, cut and paste willgenerally move the selected object(s) to the front (as will any editing action such as reshapingor changing style).

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Cut and paste can also be used to move data from one layer to another. Cut from one layer(which must be editable), make another layer editable, and paste the cut objects back into thissecond layer. Tabular data is moved with the map object(s). Alternatively, cut the objects froma browser (the map objects are cut as well, whether or not the map layer is editable) and pastethem back into the editable layer on the map window.

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Pasting text to a map window

Pasting text (e.g. text cut from a wordprocessor, as distinct from a text map object) into a mapwindow will paste the text as a text object in the current text style at the centre of the mapwindow (it can of course then be moved elsewhere). It will not overwrite a highlighted textobject on the map or paste to an insertion point placed with the text tool.

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Cutting or copying text from a map window places a text map object in the clipboard which willbe pasted back into its original geographic position in its original text style.

Cut and paste within dialogue boxes

As with all Windows programs, text can be cut and pasted between fields in dialogue boxesusing Ctrl-X, Ctrl-C and Ctrl-V. Highlighted text will be replaced by pasted text or insertionwill occur at the current cursor position.

Cut and paste to other programs

The behaviour of cut and paste to other Windows programs is determined by the options setunder Copy to Clipboard which is reached through Options>Preferences>System Settings:

Enable Copy TEXT to Clipboard to copy tabular data, Copy BITMAP to Clipboard to copymap data as a single bitmap representation and Copy Metafile to Clipboard to copy map dataas individual (vector) objects. All three types of copy can be enabled simultaneously.

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In graphical applications, such as a drawing package, Edit>Paste will paste the bitmap bydefault. In text applications, such as a wordprocessor, Edit>Paste will paste the tabular data bydefault. To paste the bitmap or metafile, use Edit>Paste Special and choose Bitmap or Picturerespectively.




6 When pasting into a text application, such as a wordprocessor, the fields are pasted with tabcharacters between them and Return at the end of each record. When pasting into aspreadsheet, fields should end up neatly in columns.


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OBJECT LINKING AND EMBEDDING

MapInfo map windows can be dragged or pasted into OLE version 2 container applications suchas Microsoft Word 6, creating an embedded OLE object 'MapInfo Map'. This object can bemanipulated using a subset of MapInfo commands by double-clicking on the object in thecontainer application (the object border and the menu and tool bars change appropriately):

? Object linking and embedding is only available in 32 bit MapInfo (Win 95 or Win NT). For 16bit MapInfo, the map window is pasted as a bitmap.

Drag and drop

To drag a map window to an OLE container application, select the drag and drop tool ,click anywhere on the map window, drag and drop onto the destination application window. Ano-go icon will show in areas where the map object cannot be pasted.

Map windows can also be dragged and dropped onto the MapInfo desktop, in which case aclone of the map window is created with full MapInfo functionality.

Copy and pasteTo copy and paste a map window into an OLE container application, make the map windowactive and remove any selection using Query>Unselect All. Copy the map window to theclipboard with Edit>Copy Map Window (Ctrl-C)4 and paste into the container applicationwith Edit>Paste Special.

h Edit>Paste Special allows you to select display of an icon labelled 'MapInfo Map' within thedestination application, as an alternative to the map window itself. This makes it quicker tomove around in the destination document, as you don't have to wait for the map(s) to redraw.




6For more information on object linking and embedding, see MapInfo Reference pages 56 - 57.

4 Edit>Copy Map Window is only available if no objects are selected on the map window.


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MAP OBJECT STYLES

The style of symbols (point objects), lines (line objects), regions (area objects) and text (textobjects) can be changed with the style entries on the Options menu or their toolbox andkeyboard equivalents:

Object type Toolbox icon Keyboard shortcut Options menu entry

Point/symbol Alt F8 Options>Symbol Style

Line/polyline Shift F8 Options>Line Style

Area/region Ctrl F8 Options>Region Style

Text F8 Options>Text Style

Selecting the menu entry or toolbox icon will display the appropriate style dialogue. Clicking onthe pull-down lists will display the alternative symbols, line and fill styles, colours etc. available.

Scope of application of styles

Changes made in the style dialogue box apply: h

To select objects on the currently active map window: the map layer must be editable;

To any objects of the same type (point, line, area or text) which are drawn until anotherstyle change is made.

You can also modify the style of an object, and all subsequent objects drawn, by clicking thestyle button on the object information dialogue (see below).

MapInfo's behaviour in changing both the style of selected objects and the default style for thattype of object, is contrary to normal Windows conventions (where the default style is changedonly if no objects are selected and can be extremely frustrating). It is to be hoped that this'feature' will be fixed in a future version.

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Why styles don't change

The style of selected map objects will only change if they are in the editable layer. Check thatthe objects whose style you are trying to change show editing handles.

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If the objects are in the editable layer, check for style override (page 82). If style override is onfor the layer containing the objects, the objects will display with the styles specified under styleoverride, whatever the individual styles applied to the objects. Your style changes will havebeen made, but they will only show when style override is turned off.

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Point object style

The Font list allows selection of any of the Windows fonts installed, including special MapInfofonts. The default is MapInfo Version 3 compatible symbols, which is not a True Type font. Nin the font pull-down indicates a null symbol, i.e. no symbol will plot. Maximum symbol size is48 point. Minimum size in the pulldown list is 9 points, but smaller sizes can be typed in andare generally useful down to about 4 point.

Rotation, Background and Effects are only available for True Type fonts. Rotation gives theangle of rotation in an anticlockwise direction. The different backgrounds (None; Halo; andBorder) are exclusive - only one at a time can be selected - whereas the effects (Drop Shadowand Bold) can be applied together.

New symbols can be defined through the Symbols MapBasic application, supplied withMapInfo, or created as bitmaps in the CustSymb directory (see page 246 for details).

Line object style

Line styles are limited to those provided by MapInfo. There are a number of conventionalcartographic line styles towards the end of the pull-down list of styles (shown on right, above),but the paucity of styles and the inability to create new ones is a problem for cartographicapplications.

N at the start of the list indicates a null line style, i.e. no line is drawn. Null lines areparticularly relevant for line styles associated with area object (region) boundaries (see below)which may not require borders.




6Note the line styles with a symbol at each end (arrows or blobs). These can be useful fordrawing in arrows or emphasising the ends of lines, but the quality of the arrows is poor and


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there is no choice of arrow style. A utility for creating arrows in different styles is availablefrom the GISNet MapInfo FTP site (Appendix I).

Region object style

Unchecking the box to the left of Background in the Region Style dialogue makes the fillbackground transparent, so that underlying objects can be seen through it. The pattern shown inthe Patterns list is drawn in the Foreground colour; the spaces between the hatches, dots etc.are the background.

Note that N in the line style or fill pattern lists means no line or no fill respectively. No fill istransparent, so that polygons, rectangles etc. with this fill style do not obscure underlyingobjects (even an apparently empty fill will obscure underlying objects, because it is a solid fillin the colour white).

Text object style




6 Text style applies to the whole of each text object - the style cannot be changed for anindividual word or other sub-string. Individual text objects can be rotated, justified and spaced


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using the Text Object dialogue (see below): these are not available as part of the text styledialogue (page 120), which is limited to setting the font styles.

Text sizes

Text font size is a rather complex issue, because font sizes behave differently for text objects ona map window, labels on a map window and text on a layout.

Text map objects

On a map window, point size has no intrinsic meaning. Text maintains a constant geographicsize and text point size is measured relative to the screen.5 As you zoom in or out, text objectswill become larger or smaller, and the point size (as shown in the text style dialogue) changesaccordingly.

! If you click OK in the text style dialogue, the default style for future text objects will be set tothe point size and font indicated. New text objects are drawn at this default point size relativeto the current screen, so they will be geographically large if drawn on a zoomed-out map, smallif drawn on a zoomed-in map. The style of text objects on layouts is also reset.

Object labels

Text labels on a map window (i.e. labels created with the labelling function or label tool)maintain a constant size relative to the map window, whatever the zoom. If the text styledialogue is opened with labels selected, it will show the same point size whatever the mapscale. Labels become larger in proportion to other map objects, and the space between them, asthe map is zoomed out, smaller as it is zoomed in. Point size, and other aspects of text style, sethere do not affect future text objects on maps and layouts.

Layout text

On a layout window, text point size is the actual point size at which the text will print. Althoughthe text gets larger or smaller as you zoom in or out, its point size stays the same. Point size,and other aspects of text style, set here does affect future text objects on maps and layouts.

Standardising text object size

h If you have drawn or changed text objects on a map in more than one batch, your text willprobably be all different sizes. To fix this, select all the text objects, zoom in until you can seesome of them at a readable size and use Options>Text Style to set the font to the point size youwant at that zoom. All the selected text objects will be reset to the same size, even though theyare not visible on the screen. Zoom out to check that it looks right on the whole map.

For more information on text objects, see "Modifying text objects" on the following page.




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5 Point size relates to nominal screen size. Nominal screen size does not relate to monitor size but to video driverresolution. A 640x480 driver generally defines the screen as 5" high at a resolution of 96 pixels per inch. A 1024x768driver generally defines it as 8" high, at the same resolution.


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MODIFYING INDIVIDUAL OBJECTS

To modify the position, shape and style of a map object, use the Select tool to double-click on the object, or select it and choose Edit>Get Info (F7). A dialogue box is displayedgiving information about the position, extent, style and smoothing of the object (the exactdialogue will depend on the type of object - see the next section for Text objects):

If the layer is editable, this dialogue can be used to modify the position of the object, its styleand, if applicable, the size, aspect ratio, smoothing, font, justification and text orientation. If thelayer is not editable, these characteristics are displayed but cannot be modified.

Clicking on the Style button brings up the style dialogue box appropriate to the type of object,as described in the previous pages.

Note: new colours can be defined using Options>Custom Colors (page 247). Custom coloursare also available by clicking the ellipsis (...) at the end of the colours pulldown lists in each ofthe style dialogues.





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Modifying text objects

Text entered with the text tool appears in the current text style. To edit text after it hasbeen typed, or to change its style, double click on it with the Select tool, which will bring up thetext object dialogue:

h Font, character size, style (bold, italics etc.) and special effects such as haloing can be changedby clicking on the Style button at the top right, which brings up the Text Style dialogue (page118). Note that changes to the text style affect future text objects as well as the current object.

The text can be rotated anti-clockwise by the amount given under Rotation Angle. The text canalso be rotated by dragging the handle just below and to the right of the text (labelled 1 below)when it is highlighted on the map window:

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1

2

If either of the label line options (Simple line or Arrow line) is activated, MapInfo will draw aline when the text is dragged away from its original position. This line connects the text withthe centroid of its original position. The end of this line has a handle (labelled 2 above) whichcan be dragged back so that it points at the desired location.





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RESHAPING OBJECTS

CHANGING SIZE AND PROPORTIONS

Whenever a line or area object is selected in the editable layer, its overall shape (aspect ratio)can be changed by dragging the edit handles (page 85). Hold down the Shift key while draggingthe handles to rescale the object in proportion (i.e. without changing its overall shape) or theCtrl key to rescale around the centre of the enclosing rectangle. Shift and Ctrl can be helddown together.

NODE EDITING

For simple lines, arcs, polylines and polygons, the shape may also be changed by movingnodes, as follows:

• Select the object to be modified;

• To enter reshape mode, choose Edit>Reshape (Ctrl-R) or click the icon;

• When reshape mode is active, the Reshape tool icon will show as pushed in andhandles will appear on each node of the selected object:

When two nodes coincide exactly on the screen they do not show, because the second nodecancels out display of the first (page 85).

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Simple lines and arcs only have two nodes, one at each end, which may be dragged to reshapethem. Additional nodes can be added to simple lines, but not to arcs, with the node additiontool (see below). To reshape arcs, ellipses or rectangles by node editing, first convert to apolyline or polygon using Objects>Convert to Polylines or Objects>Convert to Regions.

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Selecting nodes

In reshape mode, the Select tool allows selection of individual nodes rather than the object as awhole (clicking on another object selects the object and retains reshape mode). Clicking on anode selects it. The currently selected node is shown by a hollow handle (small square).

Clicking on additional nodes while holding down Shift selects multiple nodes. If the nodeclicked is not the next node along from the currently selected node(s), all intermediate nodeswill also be selected.

For polygons, Shift-click selects all intermediate nodes in the shorter path between the nodes.Ctrl-click selects all intermediate nodes in the longer path between the nodes.

Ctrl-click on an already selected node selects all nodes in the object.

Deleting and copying nodes

The current set of selected nodes can be deleted with the Delete key or Edit>Clear, and deletedor copied to the clipboard with Edit>Cut (Ctrl-X) or Edit>Copy (Ctrl-C).

Multiple nodes deleted or copied to the clipboard are pasted back as a polyline.

Moving nodes

The currently selected node(s) can be moved by dragging with the Select tool while inreshape mode. If multiple nodes are selected, drag one of them and the rest will move by thesame amount.

Note: There is a one second delay after the mouse button is pressed before the node(s) can bedragged. This delay exists to avoid inadvertent reshaping of objects when the mouse is clicked toselect a node and moved at the same time.

h If you have coincident nodes in two objects (for example, two rivers which were snapped to joinat a node, or a shared boundary between two polygons drawn with autotrace), moving nodes inone object can (optionally) move the corresponding node in the other object. This behaviour isenabled through Options>Preferences>Map Window (page 244).

? MapInfo will not search through all layers for duplicate nodes - the objects must be in the samemap layer. To ensure that coincident nodes are moved together, they should be drawn orpositioned using snap mode (page 125).

Moving centroids

h If object centroids are shown for closed objects (enable using Map>Layer Control>Displayand check Show Centroids) they can also be moved (but only within the outline of the object).This may be useful as a means of controlling the position of automatic object labelling or theposition of bar charts, pie charts or graduated symbols on thematic maps (labels and thematicobjects are all placed relative to the object centroid). Note that moving the centroid does notmove existing labels. Moving the centroid may affect marquee select, radius select, boundaryselect and spatial joins (polygon within another object) which are all based on the position ofthe centroid.





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Adding new nodes

Add new nodes to a line, polyline or polygon by activating the Node addition tool andclicking anywhere on the outline of the object to create a new node at that point. The node canbe dragged to a new position, if required, before releasing the mouse button. Simple lines areconverted to polylines by the addition of nodes. Nodes can only be added to arcs, ellipses andrectangles by first converting them to a polyline or polygon (page 127).

The node addition tool can only be activated when in reshape mode. ?

Smoothing

Use Objects>Smooth to convert a jagged outline (defined by the nodes recorded - left handdiagram) into a smooth curve (right hand diagram). Smoothing can only be applied to polylineobjects. Select Objects>Unsmooth to switch off smoothing.

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Unsmoothed Smoothed

Note that objects are only smoothed for display - if you export the data the original X,Ycoordinates of the nodes on the line are exported. The example above shows the position of thenodes - they are the same for both the smoothed and unsmoothed versions.

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Curves can be smoothed by the creation of additional nodes using a program in Curve.Zip onthe GISNet MapInfo FTP site (Appendix I).





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NODE SNAP

It is often desirable for objects to meet up cleanly - for example, tributaries will join riverswithout a break, power lines should run from pylon to pylon, and triangulation lines should runprecisely from the triangulation points to the target feature. If two objects are digitisedseparately, they may appear to meet precisely, but zooming in will invariably show amisalignment.

To avoid this problem, and to speed drawing and reshaping of features which should join up,MapInfo provides node snapping. Snap mode is enabled by pressing S when a map window isactive (whether or not there is an editable layer). The status bar at the bottom of the screen willshow SNAP.

? When in snap mode, crosshairs will appear on the nearest node whenever the mouse or digitiserpointer comes within the snap distance (see next page) of a node.6 The nodes to which thecrosshairs snap can be in any layer:

Crosshairs indicate node to which current object will snap

Mouse pointer indicates current mouse position

h If the current tool is a drawing tool, any node created when the crosshairs show will be createdat the position of the crosshairs, i.e. coincident with the nearest node, rather than at the actualposition of the mouse or digitising pointer. Snapping also occurs with other tools allowing, forexample, quick selection of nodes with the select tool, dragging of nodes to snap with othernodes, zooming on a specific node, radius select from a node or accurate measurements of thedistance between two or more nodes.

? Although the crosshairs will snap to nodes in any layer, only nodes in the editable layer can bemoved or deleted, and any nodes or objects created will be in the editable layer.

When selecting an object in snap mode, the displacement arrows ( ) will snap to a node inthe selected object if one falls within the snap distance. While the object is being dragged, thedisplacement arrows will continue to snap to nodes (in other objects) which fall within the snapdistance, so the object can be positioned precisely with the node you selected coinciding with anode in another object.

h When in snap mode, MapInfo is continuously searching for nodes to snap to as you move thepointer. With complex maps or a slow machine this can slow selection and editing on the mapto a crawl. It is a good idea to turn snap mode on and off with S as required.




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6 For clarity, snap distance has been set to an unusually large value in the illustration.


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Controlling snaps

If you have trouble with things snapping inadvertently, use Options>Preferences>MapWindow to change the snap tolerance:

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The default snap tolerance, i.e. the distance within which the pointer will snap to a node, is 5pixels - a larger value can be entered if dealing with sparse maps or a high resolution screen.

Enabling Move Duplicate Nodes in the Same Layer causes snapped nodes in the same maplayer to be moved together, i.e. when a node is dragged with the reshape tool (pages 122 - 123)any node which was snapped to it, or to which it was snapped, will be moved accordingly:

Only nodes in the same layer as the node being moved will be moved with it, as only one layercan be editable at a time. Fortunately objects which need to join up accurately are often, thoughnot always, in the same map layer (e.g. roads or rivers joining at a node or contiguous polygonswhich must share exactly the same boundary).

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POLYGON/POLYLINE CONVERSION

Different types of line and area object can be converted to polylines or polygons. Polylines andpolygons can also be converted from one form to the other. The main reasons for doing this are:

1. to close open objects (by converting arcs and polylines to polygons)

Closed objects such as polygons can be filled and used in operations such as within-areaselection of objects or area calculations. However, polygon outlines cannot be smoothed.

2. to open closed objects (by converting ellipses, rectangles and polygons to polylines)

Polylines can be duplicated where boundaries are shared. Polylines can be combined withother polylines where features have been digitised in sections. The outlines of polylinescan also be smoothed for display (page 124).

3. to create individually manipulable nodes along the object(by converting arcs, rectangles or ellipses to polylines or polygons).

This allows the addition of nodes and selective deformation of the object. Rectanglesconvert to four corner nodes, as do rounded corner rectangles (the rounded corners arelost). Arcs and ellipses convert to multiple nodes (101 nodes per 360°, proportionallyfewer for arcs).

Conversion is carried out as follows (the layer containing the object(s) must be editable):

• Select the object(s) to be converted;

• Use Edit>Convert to Regions to convert polylines, arcs, rectangles and ellipses topolygons (regions);

• Use Edit>Convert to Polylines to convert polygons, arcs, rectangles and ellipses topolylines.

The conversion assigns the current line style (Convert to Polylines) or region style (Convert toRegions) to the objects converted. Multiple polygon regions are converted to multi-sectionpolylines not multiple polylines (i.e. they remain as one object). Point and text objects are notaffected by these conversions.

OVERLAYING NODES

Objects>Overlay Nodes creates new nodes wherever two line objects or the boundaries of twoarea objects intersect. The nodes are created on the target object(s) - see next page - whereverthey are intersected by the Current Selection.

h Overlaying nodes is useful for creating nodes at intersections of networks such as roads orrivers. You can use the same objects as both the target and the current selection - this willcreate nodes wherever the object(s) cross over themselves.




6? When nodes are displayed (in reshape mode), nodes created by the intersection of an object

with itself do not show, because they occur in pairs - the second node cancels out display of thefirst (page 85).


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COMBINING AND SPLITTING OBJECTS

MapInfo has a number of commands in the Objects menu (Combine, Split, Erase and EraseOutside) which allow one to:

• combine two or more objects together into a single object (and aggregate any tabulardata for the combined objects);

• split or erase part of one or several objects using another object as a mask or 'cookiecutter' (and disaggregate the tabular data proportionally). The mask must be an areaobject (polygon, ellipse or rectangle).

These commands apply to line and area objects only. They cannot be used on point or textobjects.

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Setting the target

A target can consist of one or more map objects which must be in the editable layer. The targetis the set of objects to which the action will be applied: modification with split, erase and eraseoutside; addition of objects with combine; creation of new nodes with overlay nodes. Only asingle object can be selected as the target for combine, whereas the other actions can be appliedto multiple target objects.

To set the target, select map objects using any of the normal methods and choose Objects>SetTarget (Ctrl-T). The target object(s) will be highlighted with a distinctive pattern (set inOptions>Preferences>Map Window). Setting a target is optional for combining objects, but isrequired for split, erase, erase outside and overlay nodes.

Objects>Clear Target reverses setting of the target object(s) - it does not delete them or affectthem in any other way. The target is cleared automatically after split and erase operations.

Combine objects

Objects>Combine turns the currently selected objects into a single object or combines thecurrently selected objects with a target object.

If no target has been set, the selected objects are combined into and replaced by a singlecomposite object. Consequently the selected objects must be in the editable layer.

If a target has been set, the selected objects are added to the target object, which must be in theeditable layer. If the selected objects are also in the editable layer they are erased, otherwisethey remain unchanged.




6You can only combine line objects with line objects (line, polyline, arc) and area objects witharea objects (polygon, ellipse, rectangle). Point and text objects cannot be combined with one-another or with anything else.

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? MapInfo gives the message 'You cannot combine linear and closed objects' if you select objectsof mixed types (line and area together), but also, rather confusingly, if you select point objectsor text objects.

The end product of combining area objects (polygon, ellipse, rectangle) will be another areaobject. If the original objects were not contiguous, the end product will be an object made up ofseveral non-contiguous parts. If two or more contiguous or overlapping objects are combined,MapInfo will eliminate the boundaries between them to form a single polygon.

? Objects>Combine will be greyed out unless two or more objects are selected from the editablelayer, or a target is set in the editable layer and at least one other object is selected.

The tabular data from objects which have been combined is aggregated to create the tabulardata for the resultant object. See "Aggregation and disaggregation of tabular data" (page 132).When combining objects with a target, No Data leaves the tabular data for the target intact.

Objects can also be combined using Table>Combine Objects using Column (page 131).

Split and erase objects

Split and erase allow one to split objects into a number of separate sections or erase parts of anobject using other object(s) as a mask or 'cookie cutter'.

To use the split and erase functions you must:

1. set the object(s) you wish to split or erase as target object(s) with Objects>SetTarget (Ctrl-T);

2. select the mask object(s) using normal selection methods. The mask objects act as a'cookie cutter' to split or erase parts of the target. The mask objects must be areaobjects - you cannot erase or split with a line object;

3. apply the required function (Objects>Split, Objects>Erase, Objects>EraseOutside).

Objects>Split creates new objects for any areas in the target objects covered by the maskobjects, and deletes that part of the original objects. Where one mask object covers two or moreseparate sections of a target object, one new object is created comprising two or more polygons,as illustrated below:





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In the example above, an inverted U (the target) has been split with two rectangles producingthree objects (numbered 1 - 3). Note that the parts of the original object which were not coveredby mask objects remain as one non-contiguous object, as do the separate parts of the new objectscreated by each mask object.

Objects>Erase erases any part of the target objects covered by a mask object. Objects>EraseOutside erases any part of the target object not covered by a mask object. Each target objectremains as one object even if the remaining sections are separated.

The tabular data attached to objects which have been split or erased can be disaggregated toprovide tabular data for the resultant object(s). See "Aggregation and disaggregation of tabulardata" (page 132).

Coping with 'islands'

Erasing is particularly useful for cleaning up digitised polygon data where polygons occur as'holes' in other polygons (for example, islands in a lake or 'islands' of one soil or vegetation typewithin a large area of another). These are best handled by digitising the broad area first, then theislands.

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Although this would display correctly, a spatial operation such as point-within-polygon wouldassign, say, a sampling location on one of the islands to two landform/soil/vegetationcategories, which is clearly incorrect. The same problem occurs with elevation bands, ifcontours are digitised as closed polygons working upwards, or for concentric buffers around aset of objects (e.g. distance bands away from rivers, roads or the coastline).

To clean up the data, select the broad area as the target, then select all the islands and useObjects>Erase. 'Holes' will be made in the target into which the islands fit.

You may need to hold down Ctrl while clicking to select islands which have disappearedbehind a larger area. Cutting and pasting an island will bring it to the front, as will changes toits display style (e.g. border colour or fill pattern).

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Creating a study-area dataset

Erasing with a mask can also be used to select data for a study area out of a larger dataset.While one can use normal selection techniques (chapter 5) to select objects within the studyarea and then save them as a new table, the trailing bits of these objects which extend outsidethe study area will also be saved. Objects>Erase Outside can be used to erase everythingoutside the study area, or Objects>Erase can be used around the edge to trim off the excess.

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If you are creating the study area only for display purposes and not for analysis, you may preferto define clipping of the map (page 99) to show only the area in question, without modificationto the underlying data.

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COMBINING OBJECTS USING TABULAR DATA

Selecting and combining objects on a map is particularly useful as way of cleaning up map data.For example, you might use it to combine two halves of a feature digitised off two separate mapsheets, combine soil classes to create a coarser classification, combine administrative districtswhich have coalesced or combine a chain of islands into one multi-polygon object for analyticalpurposes. It is suitable where there are just a few objects to combine, or objects occur in clumpswhich can be easily selected in one operation.

Selecting and combining objects on a map is not so suitable where you wish to combine largenumbers of objects scattered across the map, or where there are many different groups of objectsyou want to combine. You might, for example, want to combine dozens of small patches of soilclassification into a single multi-polygon object representing shallow stony soils, then repeat forother scattered patches to create a series of broader soil classifications.

Quite often, the information required to combine objects is stored in the tabular data. Forexample, a coarse soils classification as well as a detailed classification may be stored for eachpatch of soil; each National Park, nature reserve or exploration licence may record theadministrative region to which it belongs; sampling units may record topographic andenvironmental information which might be used to group units.

Table>Combine Objects using Column allows map objects which share the same value in aparticular column, to be combined automatically. It can create a whole series of new objects inone go, rather than producing just one new object each time you use Objects>Combine. Themenu entry will be greyed out unless you have at least one writable table open.

As with Objects>Combine, the new object can replace the objects which have been combined,or the new object can be created in a different table, leaving the original objects unaffected. Toreplace the existing objects, specify the same table under Combine objects from table andStore results in table. To create new objects without affecting existing objects, specify adifferent table under Store results in table. The table specified as the destination of the objectsmust be writable (but need not be editable on any map window).

Group objects by column specifies the column (field) holding the values which are sharedbetween multiple records. The field will normally be some sort of coded or standardised namefield, or small integer numerical values.

As with Objects>Combine, the tabular data from the objects combined is aggregated to createtabular data for the new objects. See "Aggregation and disaggregation of tabular data" (page132).





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AGGREGATION AND DISAGGREGATION

OF TABULAR DATA

When map objects are combined, split or erased, the attached tabular data for each of theobjects must be combined (aggregated) or split (disaggregated) in some way to create tabulardata for the resulting object(s).

Aggregation

For Objects>Combine and Table>Combine Objects using Column, you will get thefollowing data aggregation dialogue:

Different methods of aggregation will be appropriate for different fields. For example, ifcombining sample quadrats within a particular site, one might want to enter a Blank for thequadrat ID (since each quadrat would have a different ID), record the (shared) Value of the siteID, Sum the number of plants or artefacts recorded in all the quadrats, and Average the densityfor the quadrats, perhaps Weighted by quadrat area.

Multiple fields can be selected with Shift-click and Ctrl-click selection, and their aggregationmethods can then be changed all together by selection from the Aggregation Method options.

If you are aggregating within a single layer (i.e. the target object, if set, and the selected objectsare all in the same table), Aggregation Method will show a pulldown list of fields for Weightby.

If you are aggregating objects from one table to insert into another table (the target object is ina different layer from the selected objects, or you are combining objects from one table andstoring the resultant objects in another), Aggregation Method will show a pulldown list offields next to Value. If a target is set, Value will show the value of the selected field for thetarget object, which may be modified if required.




6Before you can select sum or average you must select the source field in the pulldown list nextto Value under Aggregation Method - until the source field is selected, sum and average aregreyed out. They will also remain greyed out if the source field is not a numeric field. Defaultaggregation method is sum for numeric fields and value for non-numeric fields.

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? Sum and average will also remain greyed out if multiple destination fields are selected and anyof the selected fields are non-numeric.

No change is only available if there is a target. Blank is only available if there is no target.

Checking the No Data box is a short cut, in cases where one is not interested in any of thetabular data for the selected objects. If there are target object(s), the data for the target object(s)will be retained intact.

Aggregation is 'remembered' from one operation to the next, so it is not necessary to reenter theaggregation specifications each time objects are combined.

Disaggregation

For Objects>Erase, Objects>Erase Outside and Objects>Split, you will get the DataDisaggregation dialogue. The choices for disaggregation are similar to those for aggregation:

Use Blank where the tabular data field is of no interest or check the No Data box if none of thetabular data is of interest. Use Value where all the objects created will have the same value (asin the name or ID of an area being split, or some classification of its content), and AreaProportion where the field represents some quantity or property of the area which can beassumed to be uniformly distributed and apportioned in proportion to the area of each of theresulting objects, such as counts of incidents or objects, total income, value or yield.

SAVING CHANGES

h Use File>Save Table to save changes made to the style, placement, nodes or tabular dataassociated with map objects. It is a good idea to do this from time to time after any importantchanges have been made. File>Revert Table will take you back to the state of the table when itwas last saved (or to when it was opened if no changes have been made).





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REDISTRICTING

Redistricting is another method of grouping or combining map objects, but one which allows a'what-if' approach to the task. When a redistrict window is opened, MapInfo groups objects intodistricts and displays information on selected fields for each district. Objects can betemporarily or permanently reassigned to different districts, and the field values arerecalculated immediately.

This allows one to investigate the effects of moving map objects from one group to another. Forexample, one might be trying to create school districts with equal numbers of pupils; allocateinspectorates with equal area or with equal numbers of monuments, shops or factories; orchoose reserved land to maximise contiguity while minimising cost.

Redistricting can also be a handy way of temporarily grouping objects to obtain statistics foreach group. While this can be done more flexibly using Query>SQL Select, using Group Byand calculating aggregates (page 132), redistricting allows you to see the spatial distribution ofthe groups created.

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Creating a redistrict window

To carry out redistricting, you must have a map window open, although not necessarily active.Use Window>New Redistrict Window to bring up the New Redistrict Window dialogue:7

The Source Table pulldown list will only show tables which are displayed on the current activemap window or the last map window which was active (e.g. if a browser has been made activebefore requesting redistricting). This is the map on which redistricting will be displayed.

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MapInfo initially groups the map objects into districts according to the value of the DistrictField selected from the pulldown list. The District Field will normally be a field indicating anexisting grouping, so that there will be several map objects for each value. However it can be a




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7 You can only have one redistrict window open at once.


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blank field, or a field with a single value throughout, in which case MapInfo will create a singledistrict.

! BEWARE: If you move an object from one group (district) to another, you will change thevalue of this field - that's how MapInfo tells which district an object belongs to.

h If you want to retain the original value of the district field, you should add a new field to thetable, perhaps called Hold_District, using Table>Maintenance>Table Structure (page 40) andset it equal to the field you want to use for districting using Table>Update Column (page 157)before you start redistricting.

? If the district field is a field with a unique value for each record, such as an ID or acontinuously varying property, you may end up with a large number of single-object groups. Ifthis results in more than 230 districts you will get a warning message and no districts will becreated.

MapInfo likes to have at least 4 characters in the district field, to allow creation of uniquedistrict values when a new district is added (see below), but will allow you to proceed with asmaller field width.

Fields to Browse will initially show the name of the District Field selected, Count, and eitherFill, Line or Symbol, depending on the type of objects being grouped.8 Additional fields can beadded from Available Fields by double clicking the field or highlighting and clicking the Addbutton. Sum and Pct are shown for all numeric fields in the table. Clicking OK brings up theDistricts Browser window:

Count shows the number of objects grouped together to make each district.

Sum shows the sum of the specified field for all objects in the group, while Pct shows the sumfor the group as a percentage of the sum for all groups. It is a pity that redistricting is limited tothe count, sum and percentage aggregates. Average and other measures of central tendencywould be useful aggregates to include. It is also unfortunate that the values are presented with afloating decimal point and varying numbers of decimal places, as this makes the redistrictbrowser hard to read.

Fill, Line or Symbol shows the way in which the group is represented on the map. This can bechanged by clicking on the fill, line or symbol in the browser, which will bring up anappropriate Style dialogue.




6

8 Where more than one type of object is selected, MapInfo only displays one style column, an issue glossed over in themanuals which assume that you will only ever select one type of object . I am not sure what algorithm is used to decidewhich style is the most appropriate, as it sometimes comes up with an inappropriate style even when all the selectedobjects are of the same type.


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District display on the map window

When the redistricting browser is displayed, the map objects which have been grouped aredisplayed on the linked map window using the fill, line style or symbol style shown in thebrowser:

MapInfo actually creates an Individual Values thematic layer on the map window, and this canbe modified like any other thematic map (see chapter 8) as well as by clicking on the style inthe redistrict browser.

Note that, for the display of districts, the redistricting browser is linked to a single map window(the last active map window at the time the browser was created) which is where the thematiclayer is added. However, selection of objects on other map windows will have the same effectas selection on the linked map window.

Reallocating objects

Whenever a redistrict browser is displayed, one (and only one) of the districts in the browserwill be selected (as shown by the solid square at the left of the browser row). This is the targetdistrict.

Whenever an object is selected on the map window, it is temporarily reassigned to the currenttarget district, its fill, line style or symbol change to the style for the target district, and thefields in the redistrict browser are recalculated and updated. This allows you to immediately seethe effect of reassigning an object to the target district. Multiple districts can be reassigned byselecting multiple map objects using all the usual techniques (see chapter 5).




6 Once you are satisfied with the reallocation, you can make the assignment permanent usingRedistrict>Assign Selected Objects. This will permanently change the value of the DistrictField for the object.

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h Deselecting objects will reallocate them to their previous districts.

Display style

Unfortunately, when you select districts which are already shaded in different colours (becausethey belong to different districts), MapInfo's highlight changes each colour differently, so itbecomes very hard to determine which districts have been selected.

h If you are using a colour display, changing the thematic mapping style to use shading rather thancolour styles (page 198) will allow the highlighting to be seen more clearly:

Changing the target district

The current target district can be changed in one of two ways.

• Click on one of the open squares on the left of each redistrict browser row. The solidsquare, indicating selection, will move to this row;

• Select one object on a map window and use Redistrict>Set Target District from Map(you will need to make the redistrict browser the active window to make the Redistrictmenu entry available). The target district is reset to the district containing the selectedobject.

Creating new districts

Use Redistrict>Add District to create a new district to which map objects can be allocated.The new district is initially created with no objects and the district field value is setautomatically (normally DISTxxx where xxx is an incrementing number). The district fieldvalue can be edited in the district browser (see below).

Editing the district field

h As noted previously, any reallocation of objects to a different district changes the value of thedistrict field. The district field value can also be changed for all objects allocated to a particulardistrict, simply by clicking in the district field in the districts browser and editing the value.





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Removing districts

Redistrict>Delete Target District removes the current target district and reallocates all theobjects in that district to the unallocated district (zero or blank value in the district field). Itdoes not delete the objects in the district. Temporarily reassigned objects remain in theiroriginal district.

Saving results of redistricting

When the redistricting window is closed, the corresponding thematic map layer is removedfrom the linked map window and the original styles are redisplayed. However, the redistrictingwhich has taken place (i.e. the changes to the value of the redistrict field) are preserved,provided they are saved using Table>Save. Changes can be removed with Table>Revert.

Browser display options

Redistrict>Options allows setting of options for the districts browser window:

Districts Sort Order determines the order in which districts will display in the districtsbrowser. Most recently used keeps the most recently selected target districts at the top of thebrowser. Alphabetical sorts them alphabetically - unfortunately, if the district field is anumeric field it still sorts alphabetically, which means they are displayed in the order 0, 1, 10,100, 11, 12, ... 2, 20, 21, 22 .... Unordered applies no sorting.

Check the Save as Default box to use the selected sorting order in future districts browsers.Show Grid Lines simply turns on the grid of lines on the browser.





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LABELLING

MapInfo provides two functions for labelling objects on the map using values extracted fromthe tabular data attached to each object:

the Label tool for labelling of individual objects. Click on the object to belabelled, at the point where the label is required;

an Automatic labelling function for labelling all the objects in a layer. Automaticlabelling is switched on with the Label check box in the Layer Control dialogue.

Labels are part of the map window, not part of the table. The same objects can be labelleddifferently on different map windows.

Labels are attached directly to objects and are always editable, whether or not the layer to whichthey are attached is editable. Labels are always on top of other objects.

Configuring labels

Prior to using the label tool or automatic labelling, use Map>Layer Control (Ctrl-L) toconfigure the labelling function. In the layer control dialogue, highlight the layer containing theobjects to be labelled, and click the Label button to display the labelling options for the layer:





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Labelling field

Objects can be labelled with any of the fields defined for the table, or an expression (MapInfoReference pages 194 - 195). This allows labelling with unique identifying information such asnames (e.g. site or geographical names) or identifiers (e.g. site reference number, sampling IDs,object or event codes, street numbers).

String functions can be particularly useful as a means of truncating long fields or picking outshort codes from the start or middle of a field, for example: Right$(SampleID,4) to pick outthe last four characters of an identifying number. Labels can also be created by concatenatingfields, for example: Mapsheet+"-"+Sitenum to concatenate the two fields separated by a dash(text between "" "" is reproduced verbatim). A line break can be inserted into the label withChr$(10).9 To use an expression for labelling, select Expression ... at the bottom of the Sourcepulldown list. An existing expression can be edited by selecting Expression ... again.

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Coded fields can be used to write a number or abbreviation for each object on the map as analternative to the symbols provided by thematic mapping (chapter 8). This can be quite usefulwhere there are a large number of values, so that letters A though Z or identifying codes mayprovide a better way of identifying objects than a plethora of symbols. The objects themselvescan be replaced with the label by specifying N (no symbol) using the object style dialogue andcentring the label (see below).

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Visibility

Custom labels (labels created with the Label tool or labels dragged away from their originalposition or for which the style or content have been modified) are always visible. They are notaffected by the visibility check box on the Layer Control dialogue or the visibility settings inthe Label Options dialogue.

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Automatic labels can be switched on and off by checking On or Off buttons in the LabelOptions dialogue, as well as by checking the Visible box in the Layer Control dialogue, orthey can be displayed within a particular zoom range (page 82). A red check mark (�) in thelabelling column of the Layer Control dialogue indicates that labels on that map layer arezoom layered, and that the map is zoomed outside the range of scales within which labels aredisplayed (pages 81 - 83).

Where there are many labels the map can become a mess, so MapInfo allows labels toeliminated selectively through Allow Duplicate Text, Allow Overlapping Text, andMaximum Labels. By unchecking duplicate text, you avoid multiple labelling of, for example,rivers which have been recorded in several short sections. Unchecking overlapping textproduces a clean map, but at the cost of losing labels for objects in proximity to one-another:this may be OK where one simply requires some representative labels rather than systematiclabelling. Maximum labels sets an upper limit on the number of labels shown.

None of these options gives the user much control over what labels are shown and which areeliminated. A better option is often to allow both duplicate and overlapping text, and then movethe labels created to space them neatly, with lines or arrow lines back to the objects (see"Styles" below) where they have been moved substantially.

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9 Other special characters can be inserted using the ASCII code, for example Chr$(09) = Tab; Chr$(32) = Space; Chr$(34)= Quote (").


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Previewing labels

Because labels maintain a constant size relative to the map window, and are generally larger onthe screen than on the printout of a map,10 it is very hard to position closely spaced labels on amap window. Zooming in shrinks the labels relative to the space available, so the result ofzooming out again is unpredictable.

h To obtain a semi WYSIWYG display of the final map, first adjust the map window to the finalshape, orientation (portrait or landscape) and coverage of the map. Set the label size to theminimum acceptable for the final map, say 4 point (it is a good idea to use a compact serifedproportional font such as Times, as you can pack in a maximum amount of legible informationin a small space). Don't worry about the appearance of the map, which is probably a mess ofoverlapping labels.

Now open a Layout window containing one frame for the map window, make sure the layoutconsists of one page (or more if you intend to print the map over multiple pages) in the sameorientation as the map and resize the map frame (holding down Shift so that its shape doesn'tchange) to fill the layout. Position the layout window beside the map window and set it to viewthe layout at 100% or larger scale (Layout>Change Zoom).

Use Layout>Options and set Show frame contents to Always - this will ensure that the layoutwindow is updated as each change is made in the map. If this proves too slow, change to Onlywhen Layout Window is Active, which means you will have to activate the layout windowafter a few changes have been made to see the effect.

You can now adjust the position of the labels on the map and observe the final effect on thelayout. The main difficulties are finding the label you want to move in the mess of labels on themap window (it may help to pull closely-spaced labels right out of the way and then move themback one by one) and finding the part of the map you are working on in the layout window.

Styles

h The text style button allows setting of the font and styles (pages 118 - 119) to be used forlabelling. Although MapInfo only shows point sizes down to 8 point in the pulldown list,smaller point sizes can be typed into the dialogue and point sizes around 5 - 6 are often suitablefor labelling large numbers of objects. Smaller point sizes can be used for output on a highresolution laser printer than are legible on the screen.

The point size of labels relative to the map window stays constant as the map is zoomed in andout, unlike text objects on map layers, which get larger as you zoom in (as did labels inMapInfo version 3). See further discussion on page 119.

h When a label is dragged away from the object labelled, a plain line or an arrowed line can bedrawn between the label and the object centroid (or the point labelled with the Label tool).Check the appropriate entry under Label lines. The style of the connecting line or arrow canalso be changed using the line style button. Plain lines generally look better than arrows if thereare lots of label lines.




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10 Since the map window is less than the whole screen and is therefore nominally only a few inches high - see footnote page??119.


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Position

Labels are positioned relative to the centroid11 of the object they are labelling by clicking oneof the Anchor Point boxes. The default 2 point Label Offset between the labels and the objectsbeing labelled is often inadequate for point objects, resulting in a label which runs into theobjects, and should be increased until the desired effect is obtained.

Checking the Rotate Label with Line box causes labels to follow the direction of the lines theyare labelling so that, for example, grid lines in the Y direction will have text running vertically.

Labels, like other text objects, can be rotated individually, or several labels can be selected androtated together, by dragging the rotation handle situated just below the right hand end of thetext.

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Seamless map layers

Label options applied to a seamless map layer (page 100) apply to all the base tables making upthe layer.

Missing labels?

If you enable labels and find that only some of your objects have been labelled, check whetherAllow Duplicate Text and Allow Overlapping Text have been enabled (page 140). If they arenot, or if a limit has been specified under Maximum Labels, then labels will be eliminatedfrom the map in a somewhat arbitrary manner. When a value is set for maximum labels, labelsare displayed in the order in which the records occur in the table until the maximum number isreached, then no further labels are displayed.

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If all your labels are missing, look to see whether a zoom range has been specified under Min.Zoom or Max. Zoom. Look for a red check mark in the labelling column in the Layer Controldialogue, which indicates that the map is outside the range of scales for which labelling hasbeen enabled (pages 81 - 83).

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6

11 Note that the 'centroid' can be moved by dragging it in object reshape mode - see page ??.


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CUSTOM LABELS

Labels which have been modified from the default position and content specified in theMap>Layer Control>Label dialogue, or positioned with the Label tool (below) are referred toas Custom Labels. Custom labels must be saved by saving a workspace. Modificationsoverride general defaults set in the Label Options dialogue and will not be lost if the defaultsare modified. Custom labels are always visible and are not affected by setting label visibilityoff.

Objects can be labelled individually by selecting the Label tool and clicking on the objectto be labelled. Labels drawn in this way are identical to those drawn with automatic labelling,but can be individually positioned within an area object or along a line. When an object isalready labelled and you click on it with the Label tool, the existing label is moved to thelocation where you clicked - you can't get more than one label for a single object.

h Where objects overlap, the label is drawn for the uppermost object in the top selectable layerfor which labelling is enabled. Hold down Ctrl while clicking to cycle through objects andlayers beneath this (page 87).

? If the new label overlaps or duplicates an existing label, and overlapping or duplicate text is notenabled, the existing label(s) will be hidden.

? If visibility is set to off in the Map>Layer Control>Label Options dialogue, or if no objectsexist at the location clicked with the label tool, a beep will sound.

Individual label style

The style of individual labels can be modified by double clicking on the label or selecting it andhitting F7. This brings up the Label Style dialogue (which should really be called the LabelObject dialogue):




6? This dialogue allows modification of the label text and style for a single label - it will not

display if F7 is pressed with multiple labels selected. Unlike the normal style dialogues,changes made to the style of an individual label will not affect the style of other labels or offuture text.


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To change the style of multiple labels, select them and use Options>Text Style (F8) or the textstyle button to display the Text Style dialogue (page 118). Changes made in this dialogue willaffect the style of future text.

h

Changing the font style in the Map>Layer Control>Label Options dialogue will modify thefont of custom labels as well as the default labels, to ensure that all labels for a particular layerhave the same text size and font. Other changes in this dialogue will only affect the drawing ofnew labels and the style of non-custom labels.

Repositioning and scaling multiple labels

The labels created by automatic labelling may require systematic displacement. For example,when labelling a grid, labels on the horizontal and vertical grid lines will often require differentalignments.

To move multiple labels, proceed as follows (labelling of a grid is used as illustration):

1. Select the labels to be moved using normal selection tools:

2. (Optionally) zoom in on a small area (one or two grid squares if labelling grids, as in thisexample):

3. With the Select tool drag the labels to their correct position relative to the objectsbeing labelled. When multiple objects are selected, all objects are moved by the sameamount. This is true whether or not all the selected objects are visible on the screen.

4. Zoom out and repeat for other labels to be moved.





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Saving labels

! The labelling status of a map layer is not part of the table itself but part of the map window. Inparticular, when labels are repositioned or otherwise modified, the changes are not saved as partof the table. To save them you must save a workspace. If you do not, the original labelling andyour changes will both be lost.

h MapInfo will warn you that changes are going to be lost when you try and close the mapwindow, remove the layer or close the table, but it may not be obvious by then what thewarning message refers to. So it is a good idea to save the workspace as soon as labels havebeen added or modified, and to resave it whenever they are further customised.

! Custom labels are invalidated by packing the tabular data (Table>Maintenance>Pack Table)on which they have been created, because MapInfo uses the record number in the table toidentify the labelling instructions in the workspace file.

Removing labelling

If no changes have been made to labelling, it can simply be turned off in the Layer Controldialogue. If changes have been made, these will be stored in any workspaces you save. To avoidthis, or to return all labels to their default position and style, use Map>Clear Custom Labels toget rid of labels you have moved or modified.

Old-style labelling

Labelling was changed substantially between version 3 and version 4. Version 3 style labellingis available through the MapBasic program AUTOLBL.MBX, supplied with MapInfo.





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SCALEBARS AND DISTANCE

The MapBasic program SCALEBAR.MBX, supplied with MapInfo, adds a button to theTools toolbar and a Scalebar entry to the Tools menu. Click the button and then click on themap to indicate where the scale bar is to be drawn (the bottom left of the scale bar will beplaced at the point indicated). The scalebar dialogue is shown on the left, and an example of ascalebar on the right:

The dialogue comes up with a default length in miles based on the area covered by the mapwindow. The value can be modified, but it is generally a good idea to stay within the sameballpark length as both the scalebar thickness and lettering are scaled proportionate to thelength. A much smaller value will lead to a tiny illegible scalebar while a much larger valuewill produce an overpowering scalebar.

The scale bar is drawn as a series of separate objects in the cosmetic layer (which isautomatically made the editable layer). Each element of the scale bar can be modifiedseparately. This can be useful for modifying the spelling of the units (e.g. kilometres,kilometres or kms) and the number of divisions labelled. To move the scalebar, select all theelements with a marquee select, and drag to a new location.

h

Scalebars do not come out well on some earth projections, and may become very distorted whenmoved to a different location. There is no real solution to this problem.

?

Measuring distances

Clicking on the Ruler icon activates a floating distance window and the distancemeasuring tool:

When you click on successive points in a map or layout window, the distance window showsthe distance from the last point clicked and the total distance between all the points clicked, inthe measurement units selected. Measurement units are set through Map>Options>DistanceUnits for map windows and Options>Preferences>System Settings>Paper and Layout Unitsfor layout windows. The distances measured on earth maps are great circle distances. Onlayouts, they are distances in layout units (i.e. distance on the printed output).




6Double click on the map or layout to halt the measuring process. The measuring tool remainsactive and can be used to make a new set of measurements. The distance window remains as afloating window even when a different tool is selected - double click its window control box toclose it.


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BUFFERING OBJECTS

The Objects>Buffer command is used to create buffer areas around point, line or area objects.Buffer areas are drawn as polygon area objects whose outline is a given distance away from theobject:

Buffers can be used to indicate spheres of influence or areas within a given distance of a featureor features, or simply to indicate the size or other characteristic of each object (although thismay be better done through the graduated symbols option in thematic mapping). Buffer objectsmay in turn be used to select other objects which lie within the zone of influence or givendistance of the features of interest.

Before buffering objects you must:

Select the objects to be buffered, using any of the normal selection methods (chapter5);

Create a new layer on the map window (which will default to the editable layer) ormake one of the existing layers editable (buffers are created in the current editablelayer).

The buffering dialogue box gives a variety of buffering options:





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The Value option allows buffers of a fixed radius (left-hand illustration below) as one mightuse to establish all areas within a given proximity of roads.

The From Column option varies the radius of the buffer according to some characteristic of theobject as recorded in the tabular data (right-hand illustration below). The From Column optioncan be used to weight the buffering towards particular classes of object (e.g. larger buffers formajor rivers than small creeks, larger buffers around wilderness than recreation areas) or simplyto represent the importance of objects (e.g. stream order, size or significance of sites,transmitter power or retail outlet size).

Variable radius buffering can also be based on an expression, which may in turn include spatialinformation. For example, buffer size could be dependant on the area of the object or itsinverse, or on its proximity to some other features.

If you select One buffer for each object a separate buffer is created around each object (aseries of point objects in this example):

Fixed distance (Value) Variable distance (From Column)

If One buffer of all objects is checked, any overlapping buffer objects are combined into asingle buffer object:

Buffers are polygon objects created in the current editable layer. If you want to be able to seethe buffered objects on the map, ensure that the editable layer is below the layer containing theobjects being buffered, or that the default region style is transparent, otherwise the buffers willobscure the objects.

?

If the objects being buffered are themselves in the editable layer, the buffers will be drawn ontop of the objects and may obscure them. To see map objects obscured by the buffers, set thefill style for the buffers to no fill or use a patterned fill and set the background to transparent -see Region Style page 118).

h




6Smoothness relates to the number of segments used for each 360 degree arc in the polygon.Increasing this value will generate a more accurate (less angular) buffer at the expense of speed.


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CONCENTRIC BUFFERS

Concentric buffers can be used in many instances where one is interested in areas of suitabilityor distance bands from features such as communication routes, transmission towers or hazards.For example, to obtain a histogram of distance of points from features of interest: buffer thefeatures concentrically (see below); carry out a point-within-polygon join (page 174); calculatean aggregate (count) for each buffer zone (page 177); plot a graph of the counts (page 201).

The MapBasic program R_BUFFER.MBX, supplied with MapInfo, adds a menu entry to theTools menu which serves to create concentric buffers at specified distance around one or moreobjects. Select the objects which you want buffered before using Tools>Concentric RingBuffers>Create Ring Buffers to bring up the following dialogue:

Specify the buffering distances for each buffer using the Radius and Units fields, and click theAdd Ring button. There is no way of removing buffer rings, so if you make mistakes you haveto click the Clear button and start again. The style and smoothness settings relate to all bufferscreated - if you require different styles for each buffer radius, they must be set after the buffershave been created.

h Concentric buffers are created in a layer called Buffer_Layer. Rename this layer to avoid itbeing overwritten in a future buffering operation, or cut and paste them into another layer (page113).

Where multiple objects are buffered, R_BUFFER creates a single buffer for all objects for eachof the buffering distances specified, which can be extremely slow.12 Unfortunately the tabulardata attached to the buffer objects, which consists of a single field Id, is set to the value 0 ratherthan being updated with the buffering distance. You may wish to edit the tabular data after thebuffers have been created using the Info tool or a browser.

? Buffering can be a very slow process when large numbers of objects (particularly line or areaobjects) are involved. While it is possible to create concentric buffers by buffering buffers, itshould be borne in mind that each set of buffers contains many more nodes/line segments thanthe preceding set, resulting in greatly increased buffering time, possibly running into hours oreven days. Concentric buffers should therefore be created by repeatedly buffering the originalobjects, as outlined in DISTBUFF.TXT (see footnote).




6

12 Instructions for manual creation of concentric buffers and speeding up the process are available from the SydneyUniversity Archaeological Computing Laboratory FTP site (ftp://felix.antiquity.arts.su.edu.au/pub/texts/distbuff.txt).


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