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ArcFuels Supplemental Material: GIS 9.x Tips and Tricks Supplemental material: GIS Tips and Tricks .......................................................................................... 1 Shapefiles: Points, Lines, and Polygons .................................................................................................... 2 Creating a New Shapefile (point, line, or polygon) .................................................................................................. 2 Editing Shapefiles: Create Polygons in a Shapefile (by digitizing) .......................................................................... 6 Editing Shapefiles: Creating Polygons in a Shapefile (by copying from another polygon shapefile) ...................... 8 Editing Shapefiles: Modify Polygon Shapes............................................................................................................. 9 Editing Shapefiles: Adding a Field ........................................................................................................................... 9 Editing Shapefiles: Editing Attributes for a Shapefile ............................................................................................ 10 Converting from Polygons to Raster Format: Conversion Tool ............................................................................. 12 Converting from Polygons to Raster Format: Spatial Analyst ................................................................................ 17 Raster Data ................................................................................................................................................ 18 Cell Size .................................................................................................................................................................. 19 Resample Cell Size ................................................................................................................................................. 19 Raster Projections ................................................................................................................................................... 22 Raster File Types and File Naming......................................................................................................................... 28 Extract By Mask ..................................................................................................................................................... 31 Converting Between Integer and Float Rasters ....................................................................................................... 34 Seaming Together two or More Pieces of Raster Data (Mosaic) ............................................................................ 36 Ensuring that Zero is the NoData Value & Making Zero the NoData Value .......................................................... 38 Spatial Analyst .......................................................................................................................................... 42 Creating a New Raster Using the Raster Calculator within Spatial Analyst ........................................................... 45 Building a Difference Raster Using the Raster Calculator...................................................................................... 51 Summarizing Data .................................................................................................................................... 53 Reclassify ................................................................................................................................................................ 53 Combine .................................................................................................................................................................. 56 Summarizing Data: Calculate Acres ....................................................................................................................... 58 Zonal Statistics........................................................................................................................................................ 61 Post-Processing: Joining Attribute Tables of Raster Data .................................................................... 67 Exporting ArcGIS Data to Google Earth ............................................................................................... 70 Updated 10-12-11

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ArcFuels Supplemental Material: GIS 9.x Tips and Tricks

Supplemental material: GIS Tips and Tricks .......................................................................................... 1 Shapefiles: Points, Lines, and Polygons .................................................................................................... 2

Creating a New Shapefile (point, line, or polygon) .................................................................................................. 2 Editing Shapefiles: Create Polygons in a Shapefile (by digitizing) .......................................................................... 6 Editing Shapefiles: Creating Polygons in a Shapefile (by copying from another polygon shapefile) ...................... 8 Editing Shapefiles: Modify Polygon Shapes............................................................................................................. 9 Editing Shapefiles: Adding a Field ........................................................................................................................... 9 Editing Shapefiles: Editing Attributes for a Shapefile ............................................................................................ 10 Converting from Polygons to Raster Format: Conversion Tool ............................................................................. 12 Converting from Polygons to Raster Format: Spatial Analyst ................................................................................ 17

Raster Data ................................................................................................................................................ 18 Cell Size .................................................................................................................................................................. 19 Resample Cell Size ................................................................................................................................................. 19 Raster Projections ................................................................................................................................................... 22 Raster File Types and File Naming......................................................................................................................... 28 Extract By Mask ..................................................................................................................................................... 31 Converting Between Integer and Float Rasters ....................................................................................................... 34 Seaming Together two or More Pieces of Raster Data (Mosaic) ............................................................................ 36 Ensuring that Zero is the NoData Value & Making Zero the NoData Value .......................................................... 38

Spatial Analyst .......................................................................................................................................... 42 Creating a New Raster Using the Raster Calculator within Spatial Analyst ........................................................... 45 Building a Difference Raster Using the Raster Calculator...................................................................................... 51

Summarizing Data .................................................................................................................................... 53 Reclassify ................................................................................................................................................................ 53 Combine .................................................................................................................................................................. 56 Summarizing Data: Calculate Acres ....................................................................................................................... 58 Zonal Statistics ........................................................................................................................................................ 61

Post-Processing: Joining Attribute Tables of Raster Data .................................................................... 67 Exporting ArcGIS Data to Google Earth ............................................................................................... 70

Updated 10-12-11

Shapefiles: Points, Lines, and Polygons

Creating a New Shapefile (point, line, or polygon)

In ArcCatalog, select a folder in the Catalog tree.

Click the File menu, point to New Shapefile

Alternatively,

right click

anywhere

within the

contents

window.

Point to New

Shapefile

Type a name for the new shapefile.

Click the Feature Type drop-down

arrow and select the type of

geometry the shapefile will

contain.

If you eventually want to calculate

an area, select a polygon.

Click Edit to define the shapefile's

coordinate system

There are several methods to create the

spatial reference. The easiest way is to

click the “Import” button and navigate

to a file which has the desired coordinate

system.

You can use the coordinate system

information from any file type:

coverages, rasters, or feature datasets

and feature classes in a geodatabase.

After finding a file with a desired coordinate

system, select OK.

Add your new shapefile to your ArcMap table of

contents.

If the Editor toolbar is not visible, right-click

anywhere on the toolbar and select Editor.

Editing Shapefiles: Create Polygons in a Shapefile (by digitizing)1

1 Bridget Naylor, USDA Forest Service, PNW Research Station, La Grande Lab, [email protected], contributed to

the Editing Shapefiles sections.

Begin editing by selecting, “Start Editing” from the Editor drop down

menu.

There are many components to editing. Please read the Editor toolbar

documentation in ArcGIS Desktop Help for more information about all the

editing options that are available.

The next few steps will focus on creating a simple shapefile and converting

this shapefile to a raster.

Make sure the “Task” is “Create New

Feature” and the “Target” is the

shapefile you just created. Use the drop-

down menus to change the task or target.

Select the sketch tool (pencil) and

draw a shape by left clicking with the

mouse.

Each left-click will result in a point,

known as a vertex. Segments are the lines

that connect each vertex.

While drawing, you can undo added vertices

by selecting Edit Undo Add Vertex

Finish the sketch by double-clicking on the

starting point or right-clicking and selecting

Finish Sketch.

Be sure to save your edits when done by

selecting “Save Edits” from the Editor

drop down menu.

Note that since our new shapefile is a

polygon, you can only save a completed

polygon. If you try to save several

vertices, your work will be lost.

When finished, select “Stop Editing”

from the Editor drop down menu.

Editing tips:

To delete a single vertex from a sketch, center the pointer over the vertex until the pointer

changes. Right-click, then click Delete Vertex.

To delete the entire sketch of the feature you are creating, position the pointer over any part of the

sketch, right-click, and click Delete Sketch, or press Ctrl + Delete.

To finish a sketch, you can double-click the last vertex of the feature or press F2.

You can add an additional shape of a line or polygon feature to the sketch by right-clicking over

the feature with the Sketch tool and clicking Replace Sketch.

Editing Shapefiles: Creating Polygons in a Shapefile (by copying from another

polygon shapefile)

In ArcMap, add a new empty shapefile to the table of contents.

Select Editor and click Start Editing from the Editor toolbar.

Click the Target layer drop-down arrow and click the layer to which you want the copied feature

to belong.

Click the Edit tool.

Click the feature you want to copy. Hold down the Shift key while clicking features to select

additional features.

Click the Copy button on the ArcMap Standard toolbar.

Click the Paste button on the ArcMap Standard toolbar. The feature is pasted on top of the

original feature.

Editing tips:

Using Cut and Paste (rather than Copy and Paste) will only transfer geometry. Attributes are not

pasted, even if the source and target layers are the same or have identical schema. The appropriate

geodatabase behavior and default or null values will be populated in the target layer

If attributes are not copied, you can copy and paste the individual attributes or use the Attribute

Transfer tool on the Spatial Adjustment toolbar to pass along the existing attribute values to the

new features

Editing Shapefiles: Modify Polygon Shapes

In ArcMap, add a shapefile to the table of contents.

Select Editor and click Start Editing from the Editor toolbar.

Click the Target layer drop-down arrow and click the layer to which you want to edit.

Click the Current Task drop-down arrow and click Reshape Feature.

Click the Edit tool.

Click the feature you want to reshape.

Click the tool palette drop-down arrow and click the Sketch tool.

Create a line according to the way you want the feature reshaped.

Right-click anywhere on the map and click Finish Sketch. The feature is reshaped.

.

Editing Shapefiles: Adding a Field

With the attribute table open on the file of interest (can be raster or polygon), select Options, then Add

New Field.

Proceed to the next section to learn how to populate this new field.

Editing Shapefiles: Editing Attributes for a Shapefile

The Attributes dialog box allows you to view and edit attributes of features you have selected in your map

when you are in an edit session. You can open it by clicking the Attributes button on the Editor toolbar.

Name the file and Select a Type.

For numeric fields: use Float or Double if

decimal points are important; use Long or

Short Integers if decimal points are not

important.

For text fields: use text and enter the length

(or number of characters needed). You will

not be able to enter text that contains more

characters than the length.

Leave the Precision and Scale set at 0.

The left side of the dialog box lists the features you have selected. Features are listed by their primary

display field and grouped by layer name. The number of features selected is displayed at the bottom of the

dialog box.

o Click the Editor menu and click Start Editing.

o Click the Edit tool on the Editor toolbar.

o Select the features whose attributes you want to edit.

o Click the Attributes button on the Editor toolbar.

o Click the feature on the left side of the dialog box.

The layer's attribute properties appear on the right side of the dialog box, and the feature flashes on the

map.

o Click in the Value column on the right side and type the attribute value.

o Press Enter.

o Click the Close button to close the dialog box.

Editing tips:

You can change the primary display field for a layer on the Fields tab of the Layer Properties

dialog box. To open the dialog box, right-click the layer name in the table of contents.

To add attributes to all selected features in a layer, click the layer name, click in the Value

column, type the attribute value, then press Enter.

To flash a feature on the map, click the primary field on the left side of the dialog box; to zoom to

the feature, right-click and click Zoom To.

Double-click a layer name to see the primary display fields representing the selected features in

the layer. Double-click again to hide the primary display fields.

To remove features from the selection, right-click the primary display field on the left side of the

dialog box and click Unselect.

To delete an attribute value, right-click over the value and click Delete. You can also press the

Delete key.

To undo edits, click the Undo button on the ArcMap Standard toolbar.

You can use attribute domains to create a list of valid attribute values for a feature in a

geodatabase.

You can also view and edit attributes using the table window.

The right side of the Attributes dialog box

contains two columns: the attribute fields of

the layer you are viewing, and the values of

those attribute properties. The attribute fields,

such as ZONING and PARCEL_ID, are listed

under the Property column, and their values

are in the Value column.

The attribute values that appear on the right

side of the dialog box depend on what you

click on in the tree on the left side of the

dialog box.

When editing attributes, you can perform calculations using the field calculator in the table

window.

You can also view and edit attributes using the table window.

You can also edit attributes in the table window. An attribute table window can show you the values for

all features in a layer, not just those selected. Editing attributes through the table window allows you to

quickly make changes to several features (records) at once using the Field Calculator. In addition, the

table window allows you to add and delete fields and customize how the fields appear by setting up field

aliases, hiding fields, and so on.

o Click Editor on the Editor toolbar and click Start Editing.

o Open the table.

o Click the cell containing the attribute value you want to change.

o Type the values and press Enter. The table is updated.

If you need to make the same edit to numerous rows, select all of the rows which you are interested in

changing to the same value (they will be blue). Then, right-click on the field which will be modified and

select Field Calculator. Ignore the error message by clicking Yes (this error message will only appear if

you are not currently in an Edit Session). Type the changed value into the Field Calculator and click OK.

Converting from Polygons to Raster Format: Conversion Tool

Open

ArcToolbox, if

not already

open.

Navigate to:

Conversion Tools To Raster

Polygon to Raster

Alternatively, within ArcToolbox, select the

“Index” tab. Then type “polygon” in the

keyword search box.

Select: “Polygon to Raster (conversion)”

When the tool opens, select the

shapefile you want to convert to a raster

from the “Input features” drop down

menu or navigate to the desired

shapefile using the browse button.

The “Value field” selected here will

become the Value in the output raster. If

you are creating a raster of treatment

units, you would likely want the Value

field to be the unit ID number.

Name the “Output Raster Dataset” with

no file extension. See previous section

on file types and naming for more

information.

NOTE: Explore the Cell Assignment option if you are not happy with the produced output raster. Cell

Assignment will determine how a value is assigned to a cell if more than one feature falls within a cell.

NOTE: The Priority field option is used when there are overlapping polygons within your shapefile.

Change the “Cell Size” to match the

size of the other raster data sets you

are working with.

If you plan to use this newly created

raster to perform further analysis,

comparisons, etc. with any other

raster data, you will need to ensure

everything is aligned. See the Spatial

Analyst section of this GIS Appendix

below for a visual depiction of raster

alignment.

You can ensure that all of your data

are aligned by modifying the

Environments settings.

After clicking

Environments, Expand the

General Settings.

Scroll

downward

to the “Snap

Raster”

drop down

list.

Select one of

your existing

rasters as

the Snap

Raster. This

ensures that

your data

are properly

aligned.

Click OK to

return to the

Polygon to

Raster tool

and OK to

initiate the

tool.

Converting from Polygons to Raster Format: Spatial Analyst

This similar process, only with fewer processing options, can be

accomplished through a tool accessed through the Spatial Analyst

Toolbar.

If the Spatial Analyst toolbar is not visible, right-click anywhere

in the toolbar and select “Spatial Analyst”.

Before proceeding further, you need to set up your Spatial

Analyst options. See the Spatial Analyst section below to learn

how to set up the options.

From the Spatial Analyst drop-

down menu, select Convert

Features to Raster

NOTE: If any features are selected in the layer you choose as the input, only those selected features will

be converted.

Raster Data

A raster, also known as a grid, consists of a matrix of cells (or pixels) organized into rows and

columns where each cell contains a value representing information, such as fuel model, elevation, etc.

Rasters are digital aerial photographs, imagery from satellites, digital pictures, or even scanned maps.

Rasters contain either discrete (e.g., fuel model) or continuous information (e.g., elevation) or are simply

pictures (ESRI 2009).

When adding raster data to your ArcMap table of contents, you may be prompted to build pyramids. It

does not really matter if you choose Yes or No; however selecting Yes will speed up viewing the data at

varying scales.

Click the “Input features” drop-down arrow and

select the feature layer you want to convert to

raster.

Alternatively, click the browse button to

navigate to the location of a feature dataset.

The “Field” selected here will become the Value

in the output raster. If you are creating a raster of

treatment units, you would likely want the “Field”

to be the unit ID number.

Change the “Cell Size” to match the size of the

other raster data sets you are working with.

Name the “Output Raster Dataset” with no file

extension. See previous section on file types and

naming for more information.

Click OK.

Cell Size

Resample Cell Size

If the cell size of one or more of your raster datasets is unlike the others, you will need to use the

Resample geoprocessing tool. Realize that when you resample, you cannot gain any more detail in your

To determine the cell size, right click on your raster in the table of

contents and select “Properties”.

Go to the “Source” tab

and view the “Cellsize

(X,Y)”.

In this example, cell

size is 30 m x 30 m or

900 m2.

If the cell size of

one or more of

your raster

datasets is unlike

the others, you will

need to Resample.

dataset; consider resampling the raster with the smaller cell size (which has more detail) to the larger cell

size.

Open

ArcToolbox if

not already

open.

Navigate to:

Data Management Tools Raster Raster

Processing

Select: “Resample”

Note that in this scenario Resampling Technique can be left as the default. Consider the other options if

you plan to drastically change cell size.

When the tool

opens, select

the raster to

resample

from the drop

down list.

Name the

output raster

(with no

extension; see

raster file

types above).

Type in the

desired output

file size and

then click

“Ok”.

Alternatively, within ArcToolbox, select the

“Index” tab. Then type “resample” in the

keyword search box.

Select: “Resample (management)”

Raster Projections

Before beginning a project, it is important to ensure that all of your raster data and dataframe are in the

same projection. Some processes may function properly with varying projections, but others will not, so it

is best to eliminate a projection issue as a potential source of error later in your analysis. The projection of

your dataframe is established when the first file is added to the table of contents, but can be changed at

any time.

To determine the projection of your dataframe, right click on the Layers

icon in the table of contents and select “Properties”.

Select the Coordinate

System tab and view the

dataframe’s current

coordinate system.

The coordinate system of

the dataframe is

established when the first

file is added to the table of

contents.

There are several methods

to change the coordinate

system of the dataframe.

The easiest way is to click

the “Import” button and

navigate to a file which has

the desired coordinate

system.

To determine the projection of your data, right click on your raster in

the table of contents and select “Properties”.

Select the

Source tab

and scroll

down to

“Spatial

Reference”.

To change

the

projection,

you will

need to

follow the

next few

steps.

NOTE: There is a difference between the Project Raster and Define Projection tools. Define Projection

is used when there is no projection associated with your data. Project Raster is used when there is a

projection, but you would like to change it.

Open

ArcToolbox if

not already

open.

Navigate to:

Data Management Tools Projections and

Transformations

Select: Project Raster

Alternatively, within ArcToolbox, select the “Index”

tab. Then type “project” in the keyword search box.

Select: “Project Raster (management)”

When the tool

opens, select the

raster you would

like to change the

projection of from

the drop down list.

Name the output

raster (with no

output extension;

see naming raster

file types below).

Select a new

projection using .

There are several methods to change the spatial

reference. The easiest way is to click the “Import”

button and navigate to a file which has the desired

coordinate system.

You can use the coordinate system information

from any file type: coverages, rasters, or feature

datasets or feature classes in a geodatabase.

Depending on the output

coordinate system chosen,

you may have to select a

geographic transformation.

Choose the transformation

that is most appropriate for

your geographic location.

When in doubt, choose

NADCON. NADCON is the

federal standard for

transformations within the

continental Unites States.

Select OK.

After finding a file with a desired coordinate

system, select OK.

Raster File Types and File Naming

All raster file types have the same icon in ArcCatalog . The file types a fuels planner will likely see

and/or work with most are: ASCII rasters, ESRI rasters, and ERDAS Imagine rasters.

ASCII Raster– file extension .asc (e.g., fuel_mdl.asc). ASCII file types are exported from fire behavior

programs such as FlamMap and FARSITE and need to be converted to ESRI rasters (see below) before

they can be viewed. ASCII raster names do not have a character limit, but it is good practice to keep

names under 13 characters, as they will need to be shortened when converted to an ESRI raster. If you are

working with ArcMap and ArcCatalog version 9.2, you can tell if a file is an ASCII file type by

previewing it in ArcCatalog or adding it to the ArcMap table of contents. It will be solid grey in color.

ERDAS Imagine – file extension .img (e.g., fuel_model.img). Imagine file types can be produced using

the program ERDAS imagine (program burn severity data is often manipulated with). Fuels planners will

likely not need to work with .img rasters. However, since it is the default output file type for many

geoprocessing tools within ArcToolbox, it is important to be aware of this file type so that you erase the

.img before naming your ESRI raster files.

When previewed in

ArcCatalog, ASCII files

are solid grey in color.

ESRI Raster – no file extension (e.g., fuel_mdl). ESRI girds are the typical file format used, native to

ArcMap. ESRI rasters have a 13 character file name limit. There are two types of ESRI rasters, Integer

and Float.

Integer- Discrete attributes for an integer raster are stored in an attribute table. Integer rasters can store

only whole numbers, therefore all decimal points are rounded up or down when data are converted to an

Integer. Summarizing data for NEPA, for example, can be achieved by exporting the attribute table of an

integer raster to Excel.

Float- The cells in this type of raster do not fall neatly into discrete categories and therefore do not have

an attribute table, the data are continuous. Float rasters can store numbers with decimal points. Burn

probability is inherently a float raster because it is expressed as a fraction of 1 and therefore requires

storage of decimal points, but can be converted to an integer for easy analysis by multiplying the raster by

1000 (using the Raster Calculator) or reclassifying the raster into new categories. See the Spatial Analyst

and Reclassify sections for more detail on this topic.

Determine whether or not the file you are working with contains Integer or Float data by right-clicking on

the file. If “Open Attribute Table” is not grayed out, you have integer data. If the “Open Attribute Table”

is grayed out, you have float data.

Geoprocessing tool

showing default .img

in file name.

In ArcMap and ArcCatalog version 9.3, the ASCII file extensions are visible; therefore you can tell what

file type you are working with without previewing the data. This may not be the case with ArcMap and

ArcCatalog version 9.2. If you do not see the .asc extension on your ASCII file types in ArcCatalog, go to

Tools and select Options. When the window pops up, select the File Types tab. Select New Type. Enter

the file extension .asc and type ASCII as the Description of Type.

This ESRI raster contains float data because there is no attribute table

available to view when right-clicking on the file.

Tools Options

File Types New

Type

Extract By Mask

Extracting by mask is a way to clip raster data to a desired shape.

Type asc into the File extension.

Type ASCII as the Description of

Type.

Open

ArcToolbox if

not already

open.

Navigate to:

Spatial Analyst Tools Extraction

Select: “Extract by Mask”

Alternatively, within

ArcToolbox, select the

“Index” tab. Then type

“extract” in the keyword

search box.

Select: “Extract By Mask

(sa)”

When the tool opens,

select the raster layer

you would like to clip

from the Input raster

drop down list.

Select the file (raster or

vector) that represents

the boundaries of the

area from the feature

mask data drop down

list.

Name the Output Raster.

Click OK.

Converting Between Integer and Float Rasters

Converting between Integer and Float rasters is easily achieved through the Int geoprocessing tool within

ArcToolbox.

Open

ArcToolbox if

not already

open.

Resulting fuel model layer,

clipped to a fire boundary.

Navigate to:

Spatial Analyst Tools Math

Select: “Int”

Alternatively, within ArcToolbox, select the

“Index” tab. Then type “int” in the keyword

search box.

Select: “Int (sa)”

Seaming Together two or More Pieces of Raster Data (Mosaic)

Open

ArcToolbox if

not already

open.

When the tool

opens, select the

float raster from the

drop down list.

Name the output

raster (with no

output extension;

see raster file types

discussion), then

click OK.

Alternatively, within ArcToolbox, select the

“Index” tab. Then type “mosaic” in the

keyword search box.

Select: “Mosaic to New Raster”.

Navigate to:

Data Management Raster Raster

Dataset

Select: “Mosaic to New Raster”

NOTE: In this scenario the optional fields can be left as is. The coordinate system and cell size should all

be the same, because you have already ensured that everything you are working with is in the same

projection and has the same cell size (see previous section). Leave the Pixel type Bands and colormap

modes as their default values. The mosaic method field is chosen if there is overlap between the datasets.

This determines which dataset will overwrite the other, the first one in the list or the last.

Ensuring that Zero is the NoData Value & Making Zero the NoData Value

In order for the Modify Raster Values, Apply to Selected (Non Zero) Pixels in layer process to work

properly, zero (or a negative number) must be the NoData value. If zero or a negative number is not the

NoData value, ArcFuels will perform your change globally, rather than to the areas encompassed by a

specific layer.

Select the raster data sets you

would like to seam together

from the drop down list or

navigate to them using the

open folder .

Choose an output location and

the cell size that is common to

all of your data.

In ArcMap or

ArcCatalog,

right-click on a

raster data set

and select

Properties.

Under the Source

tab, scroll down

to determine the

NoData Value.

In this example,

255 is the NoData

Value.

The Modify

Raster Values

tool will not work

with the NoData

Value set to 255.

To change this,

Open

ArcToolbox, if

not already

open.

Navigate to Data Management tools Raster

Raster Dataset.

Select Copy Raster.

Alternatively, within ArcToolbox,

select the Index tab. Then type

“Copy” in the keyword search box.

Select: Copy Raster (management).

When the tool opens up,

select the raster you

want to copy from the

Input Raster drop down

list.

Name the output file,

being careful to DELETE

the .img from the name.

Enter “0” as the NoData

Value.

Click OK.

Zero should now be the NoData

value in your newly copied

raster.

Spatial Analyst

Activate the Spatial Analyst toolbar and set up your options. Select Spatial Analyst Options.

There are three tabs to review in the window that pops up: General, Extent, and Cell Size.

General Tab

Working Directory – establishes the location where your outputs will be saved.

Analysis Mask – identifies those locations within the analysis extent (see Extent tab below) that

will be included when performing an operation or function within Spatial Analyst. The mask can

be a raster or a feature class. For rasters, all input cells that fall outside the mask will not be

considered in the analysis and will be assigned the NoData value in the result. For example, you

could use an analysis mask to clip rasters to your study area or to change a fuel model within a

desired area.

Analysis Coordinate System – gives you the ability to re-project your outputs to the projection of

the data frame while processing data. If you want to use this feature, pick the lower radio button

option.

Extent Tab

The General Tab in Spatial Analyst

Options

Establish your working directory, an

analysis mask, and output coordinate

system.

Analysis Extent– establishes an area or subset of a larger dataset that will be included when

performing an operation or function within Spatial Analyst. All subsequent output rasters from an

analysis will be sized to this extent. Note that if you select your analysis mask or one of the

rasters in your table of contents as the analysis extent, you do not need to worry about the Snap to

Extent. ArcMap will automatically snap your data to the analysis extent.

Snap extent to – If you do not select an Analysis extent, you need to select one of your data sources in

your table of contents to ensure that the cells of the outputs line up with the inputs. See the graphic below

for a visual depiction of the snapping. See the Converting Polygons to Raster section of this Part 6:

GIS Tips and Tricks to learn how to align (snap) data if they are not already aligned.

Unaligned (left graphic) and Aligned (right

graphic) input (black) and output (blue)

raster data.

Analysis Extent

Cell Size – To ensure your output cell size is the same as your input, select one of the rasters in your table

of contents from the drop-down list or specify a desired cell size. See the Cell Size section of this Part 6:

GIS Tips and Tricks to review the importance of cell size and how to modify cell size.

Once your options are set, you are ready to use the features within Spatial Analyst. You need to check and

re-set these options after every time you process data using Spatial Analyst. The options will return to

their default settings after every operation or function.

The Extent Tab in Spatial Analyst

Options

If you select a raster in your table of

contents, you do not need to select Snap to

Extent. ArcMap will automatically snap

your data to the analysis extent.

The Extent Tab in Spatial Analyst Options

If you do not select an Analysis extent, you

need to select one of the rasters in your table

of contents to ensure that the cells of the

outputs line up with the inputs.

Creating a New Raster Using the Raster Calculator within Spatial Analyst

Set you Spatial Analyst options as described above. In this example, we will be creating a new raster with

the Mt. Emily demonstration data containing slopes < 30%. Under the General tab our working directory

is: C:\arcfuels\data. We do not need an analysis mask. Under the Extent tab, select the slope raster (or the

fuel model raster, as all rasters in the demonstration data all have the same extent) as the Analysis extent.

Under the Cell Size tab, select Same as Layer “slope” (or Same as Layer “fml”, as all rasters in the

demonstration data all have the same cell size).

Activate the Spatial Analyst toolbar and

select Spatial Analyst Options.

Select your working directory

(c:\arcfuels\data).

Select your Analysis Extent (Same as Layer

“slope”).

Open the Raster Calculator by selecting Spatial Analyst Raster Calculator. The syntax for the

raster calculator is as follows:

o [raster you are creating] = [raster calculation is based on] OR

o raster you are creating = [raster calculation is based on]

The first option creates a temporary raster, while the second option creates a permanent raster.

It is important to know whether your slope raster is in degrees or percent. As a rule of thumb, if

you have slope values >100, your raster is percent, since values of slope in degrees over 90 would

be infinite. The demonstration data contain values over 100 and are therefore in percent. See the

Slope Degree to Slope Percent Conversion table in Part 5: General Help for a slope

degree/percent conversion table.

Type the following in the Raster Calculator box and then click evaluate:

[new raster] = [slope] <30

This will create a new temporary raster of ones and zeros where the ones represent the area where

slope < 30%.

Select Cell Size (Same as Layer “slope”).

See the previous section for more detail

related to Spatial Analyst options.

Raster Calculator set-up to

create a new temporary raster

of 1s and 0s where 1s represent

the area of ground where, slope

< 30% .

New temporary raster of 1s

and 0s where 1s represent the

area of ground where,

slope < 30% .

Now, get rid of those 0s. Note that you do not have to get rid of the 0s in order to use the

processes demonstrated in Module 1-1. However, this is an important process to learn.

If not open already, Open ArcToolbox and navigate to Spatial Analyst ToolsExtraction

Extract by Attributes.

When the window opens, select new_raster as the input raster and name/save the output raster to

a desired location. A good name for this raster is slope30. In this scenario, we are saving to our

c:\arcfuels\data folder.

Under the Where clause, click the SQL button, and enter “VALUE” > 0. This can be done by

double-clicking on the word “VALUE” in the top box of the SQL window and using the Get

Unique Values and mathematical operators (e.g., >, <, like) buttons or by typing in the expression

manually, with the quotation marks. You can verify that your expression is valid by clicking the

Verify button. Click OK after your expression is verified to exit the query builder, then click OK

again to launch the extraction process. In your resulting raster, 0s have been replaced with

NoData values.

Verify this using the Identify button .

Open

ArcToolbox if

not already

open.

Navigate to:

Spatial Analyst Tools

Extraction Extract by Attributes

Extract by Attributes tool

showing new_raster as the

Input Raster and slope30 as

the Output Raster

Click the “SQL” button

under the “Where clause”

to build an expression that

will extract the 1s from

new_raster.

Query builder that results from selecting the

“SQL” button under the Extract by

Attributes tool.

Manually type in the phase “VALUE” > 0

exactly as shown or use the buttons within

the tool.

Verify your expression by clicking the

“Verify” button.

Click OK after your expression is verified.

Resulting slope30 raster where 1s

represent slopes < 30%.

The 0s have been replaced with

“NoData”.

Now, with your newly created slope30 raster, you can modify the fuel model layer using the

Modify Raster Values button and the process outlined in Exercise 1-1.3.

Building a Difference Raster Using the Raster Calculator

Set up your Spatial Analyst Options as shown in previous section of this Part 6: GIS Tips and Tricks.

Open the Raster Calculator from the Spatial Analyst drop-down list.

Subtract your post treatment

raster from your pre-treatment

raster.

Use your reclassified (i.e., flame

length broken into hauling

categories) or unclassified data.

In this example, post treatment

flame length is subtracted from

pre-treatment flame length.

Verify this by using the Identify button .

View the properties of

your newly created

raster (right click

properties).

Select Unique Values.

Notice the pixel count

of each value.

Positive numbers

represent a reduction

in flame length;

negative numbers

represent an increase

in flame length.

Group these values

into categories that

are meaningful to you

by selecting the values

(hold down the

control key to select

more than one)

right click Group

Values.

Label each grouping.

Summarizing Data2

As discussed in Module 1-6, you will likely want to summarize and calculate acres of each FlamMap

output within your planning area/units/values at risk.

Reclassify

This is accomplished using the Reclassify tool in ArcToolbox or the Reclassify tool in Spatial Analyst.

Note that both tools result in the same output. Use the Spatial Analyst tool if you want to reclassify only a

portion of your data. Note that if you use the Spatial Analyst tool, you will need to set up your Options

appropriately. See the Spatial Analyst section of this Part 6: GIS Tips and Tricks for more detail.

2 Chris Zanger, The Nature Conservancy, [email protected] contributed to the Summarizing Data sections.

In this example, flame length

increases are shown in red;

flame length decreases are

shown in blue; black pixels are

areas of no change.

Note that since flame length is

produced from a static run,

there should be no change from

pre- to post-treatment outside

of the treated units.

Repeat with burn probability

and other metrics of interest.

Open

ArcToolbox if

not already

open.

Navigate to:

Spatial Analyst Tools Reclass Reclassify

Select from the drop down

list or navigate to the

raster you want to

reclassify.

Choose “Value” (in this

scenario, value = flame

length) from the Reclass

field drop down list.

Click “Classify”.

Under Classification

“Method” select any method

that will allow you to change

the number of “Classes”.

If classifying flame length

into hauling categories, you

will want 4 categories. Set 4,

8, and 11 as the first three

“Break Values”. Leave the

highest break value as is.

This will result in 4

categories of rounded flame

length, 0-4, 4.1-8, 8.1-11,

and 11.1+ ft.

If you have a large area of

“No Data” or unburnable

fuels in your modeling area,

consider adding “0” as a

category by using the

“Exclusion” button.

Click OK.

NOTE: This same technique works to Reclassify integer or float data.

NOTE: Consider using five categories if you have a significant amount of non-burnable fuels within your

landscape. Reclassify the zeros into their own category, so it does not appear that “rocks” or “water” have

a flame length of up to 4 ft.

Combine

After all of your data have been Reclassified into categories that are appropriate for summarization and

your treatment units are in raster format, you are ready to use the Combine tool. A combine can also be

executed with the Raster Calculator within Spatial Analyst.

Enter the upper limit of each

hauling category into the

“New Values” column, name

the “Output Raster” and

click OK.

Open

ArcToolbox if

not already

open.

Navigate to Spatial Analyst Tools Local

Combine.

In this example,

flame length, crown

fire, and treatment

locations will be

combined.

Use the drop down

list or navigate to

the rasters you want

to combine.

Name the output

raster and click OK.

Summarizing Data: Calculate Acres

This output shows the number

of times (Count) each

combination of the values from

the combined raster (treat_loc,

cf_notrt, fl_notrt_re) occurs.

For example, there are 299

pixels within treatment unit 652

where crown fire = 1 and flame

length = 4.

In this output, the Value field

has no relevance to the data.

Next step is to add a field and

calculate acres.

From the Options

menu, select Add

Field.

Name the field “Acres” and Select Type

“Float”.

Leave the precision and scale as 0.

Right click on the newly created Acres column and Select Field

Calculator.

Select “Yes” to the warning that pops up.

You are going to calculate acres based on

your knowledge of your data’s cell size. In the

demonstration data, each pixel (cell) is 30m x

30 m or 900 m2.

Open a web browser to Google. Type “convert

900 meters squared to acres”. The following

conversion will appear.

900 (meters squared) = 0.222394843 acres

If you are using rasters with a 25 m (or any

other) cell size you will need to type “convert

625 meters squared to acres” in the Google

search engine.

Double-click on “Count” in the

Field list box. It will appear in

brackets below.

The “Count” field is the

number of 30 m X 30 m (or 900

m2) cells.

Multiply the “Count” field by

the conversion factor and click

OK.

Zonal Statistics

Zonal Statistics are used to summarize your data based on “zone” data. The output can be a table or a new

raster. Zone data are any areas within which you would like to summarize your data. In other words, if

you want to summarize the flame length within your treatment units (zones) use zonal statistics. Zonal

Statistics can also be used to pick the value within a zone which represents the majority, as described in

Module 1-7. If you want to summarize multiple layers across a zone, use the methods described in

Module 1-6.

Open the

attribute

table of the

combined

raster.

The Acres

field is now

populated.

Export this

table to

Excel

(Options

Export).

Summarize

the data by

plot

(treat_loc in

this

example)

using a pivot

table.

Open

ArcToolbox if

not already

open.

Navigate to Spatial Analyst Tools Zonal.

Select “Zonal Statistics as Table”.

When the tool opens,

select the zone data

(i.e., treatment

units).

This can be a raster

or vector data layer.

The zone field is the

attribute within the

zone data layer you

would like to

summarize across

(i.e., treatment

units).

In the treat_loc file

value = treatment

units.

The Input Value

Raster is the raster

you would like to

summarize.

In this example, this

is pre-treatment,

unclassified flame

length.

Place a check mark

next to “Ignore

NoData”.

Navigate to a saving

location and name

the output table.

Click OK.

Select the Source tab to view your table in ArcMap.

Right-click on the zonal table and select, Open.

Alternatively, navigate to where you saved your table and open it

through Microsoft Excel. It will have a .dbf extension.

Examine the

table.

Value

represents

treatment unit.

In this

example, Unit

652 has a

minimum of 3,

maximum of 65

and average of

22 ft flame

lengths.

Navigate to Spatial Analyst Tools Zonal

Select “Zonal Statistics”.

When the tool opens, select

the zone data (i.e., treatment

units). This can be a raster or

vector data layer.

The zone field is the attribute

within the zone data layer

you would like to summarize

across (i.e., treatment units).

In the treat_loc file, value =

treatment units.

The Input value raster is the

raster you would like to

summarize.

In this example, haz_units =

hazard within treatment

units.

The Statistics type in this

example, “majority” creates

a new raster which identifies

each unit based on the

majority of hazard pixels.

Navigate to a saving location

and name the output table.

Click OK.

The resulting raster will look odd. As with any ArcMap raster

process, only the “VALUE” field is carried over.

In this example, the “Value” field is the haz_unit raster.

You will need to Join the resulting raster back to the original

hazard units raster to display the hazard classifications.

Continue to the next section for instructions related to this

process.

Post-Processing: Joining Attribute Tables of Raster Data

Often, the output from ArcMap raster processes

contains only a “Value” field.

This “Value” field is the link back to the

original data source and the associated

attribute table.

To re-attach the attribute table associated with

the output, it needs to be Joined back to the

original data source.

This example continues from the previous

section on Zonal Statistics.

Right-click on the raster which needs to be

Joined back to the original data source.

Select “Joins and Relates” and then “Join”.

From the drop down list, select “Join

attributes from a table”:

1. The field the Join will be based on is

the “Value” field,

2. The table to Join to this layer is

“haz_unit”, as this is where the

“Value” field originated from, and

3. Base the Join on the “Value”, as

this is the field which is common to

the output and the original data.

Keep only the matching records, since the

original data set contained more information

(rows of data) than the output.

Click OK.

Use the “Symbology” tab within the

Layer Properties to verify that the join

was successful.

Summarized data

Joined to original data

(left).

Original data (right).

To make the join permanent, right-click on the layer.

Select “Data” and then “Export Data”.

Exporting ArcGIS Data to Google Earth

If you want to share ArcGIS spatial data for public viewing in Google Earth there is an ArcToolbox tool

that will generate KML (keyhole markup language) files from ArcGIS layers. The files can then be

distributed or posted at a Google Earth site for viewing in Google Earth.

Open

ArcToolbox if

not already

open.

Verify the cell size.

Navigate to an output folder.

Rename the file (erase the

.img extension).

Select “Raster” from the

Format drop down list.

Click Save.

Navigate to Conversion Tools To KML

Layer To KML.

Select your layer to be converted

from the drop down list. Navigate to

an output location and name the file.

ArcMap creates a KMZ rather than a

KML, which is just a compressed

KML file. There is no need to

“decompress” it.

Choose a reasonably large layer

output scale. This determines the

scale at which you can see your file

in Google Earth

Click Ok.

In windows explorer, double-

click on your KMZ file. This

will automatically open

Google Earth.

These are the flow paths

from the demonstration data.

Alternatively, navigate to

your KMZ, by selecting File

Open.