developing a geographic information system

8/4/2019 Developing a Geographic Information System

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DEVELOPING A GEOGRAPHIC INFORMATION SYSTEM (GIS)

TOOL FOR EXTENSION PURPOSES IN MAURITIUS

M Chung Tze Cheong, R Appave and S Jamala

Mauritius Sugar Industry Research Institute

ABSTRACTGeographic Information System is essentially a tool to help visualize information in a

spatial way. This paper illustrates how extension officers can use GIS to manage

individual farmers plots, in the large and often remote areas under their responsibility. This application product is a prototype developed, using Visual Basic, map objects and

map files

generated from ARCInfo. It has a set of menus and buttons with which officers mayquery the

geographic database of the project area. In this instance, data files supplied by the

Farmers Service Centre, responsible of farmers fields in St Felix factory area, have been

integrated with the map files prepared by MSIRI into a geographic database. Monitoring

of yield with respect to the current practice may then be followed and handy documentsproduced for field visits. Observations from field visits may also be fed into the database

so that information accessible to officers as well as decision-makers can be updated.This pilot project is an example applicable to crops other than cane. As illustrated in this

study, it

allows a dynamic evolution of the system with almost 'real-time' feedback at field level.Specific

extension goals set for the target farmers could then be grouped geographically viz,

irrigation, ripener application and mechanization projects.

Keywords: Geographic Information System, farmers' plots, extension officers,

decision-makers

INTRODUCTIONIn an effort to increase the sugar cane production of small planters, inclusion of

information technology (IT) as part of the extension tool for field officers is becoming a

necessity, as extension officers are called upon to cover geographically remote anddispersed areas. Data collection on their part, and their organisation into an appropriate

format can therefore be very tedious; consequently the development of a tailored,

process-based GIS application will be of great help to the extension officers.As a result of meetings and discussions held with the officers of St. Felix Farmers Service

Centre

(FSC) on their current needs in data manipulation, it became clear that the extension

officers are not all familiar with the computer environment, and do not have much time tolearn the GIS software. To develop the application screens, the design of the GIS

prototype has therefore been focused on spatial

data query, display, and printing and the fact that no prerequisite knowledge of GIS isnecessary.


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MATERIALS AND METHODS

Data preparation

The source data, which comprised of paper maps and excel files with farmers' data, wereprovided by

the St. Felix FSC for three sub-blocks of St. Felix Factory Area. The spatial data were

prepared withthe Arc/Info GIS software. Minor changes in the geographic database were then done in

the desktop

module ARCView, as the map files were linked with descriptive database for shape files

creation

through a common key id.

Database structureThe databases received as excel files were imported in Microsoft Access 97, and classified according to

years and locality sub-blocks. The key id is devised through the concatenation of factory area, locality

sub-block and plot number to represent a unique identity for each record (Table 1, Figure 1). The

same uniqueness is applicable to the rest of factory areas of the country. A similar key was applied to

the map files or shape files.

Table 1 Database structure for farmers plots as received from the FSC


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Figure 1 Database files in Access

Application development environmentThe customisation development makes use of the object-oriented approach, in aninfrastructure data model, whereby data files like maps and tables, the object libraries of

standard office packages like Excel and ACCESS, and of Map Objects , are considered as

objects and components of the application development project. The existing

functionalities like charting, table display, colour palette of other software are tapped forgraphic display through referencing, and queries performed through the Structured Query

Language (SQL), made available in the Visual Basic (VB) development platform,

and a multitasked Windows environment. The Visual Basic programming language(Aitken 1998) has been used as a control container to assemble the multiple controls and

components for a rapid application development (RAD) (Figure 2)


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Figure 2 Concept of Infrastructure Model used in the application development

(adapted from R. Hartman, 1997)

Map objects are an ESRI (Environmental Systems Research Institute 1999) product,

consisting of a

collection of mapping components (viz., Map objects OCX and other programmable

ActiveXautomation) for application developers. It provides the possibility to create customised

solutions so asto meet the desktop mapping, and GIS needs of common users, through the following

facilities:

Access to a wide range of data formats ranging from standard GIS formats(ARCInfo coverages and ESRI shapefiles) to CAD formats (DXF, DWG, andDGN) to perform spatial queries.

Display data using classifications (regrouping/categorisation), graduatedsymbols, and labeling.

Pan and zoom through multiple map layers. Queries features displayed on the map

By means of map objects.OCX and a data connection string, the directory containing thedifferent map

files, and their related databases are retrieved and read. (Figure 3)


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List of OCX (Object Controls) used

Map control (mo02.ocx): a box in which map layers (shape files) are loaded. ADO (ActiveX Data Object): Data control which establishes data connection

using ODBC

(Open Database connectivity) drivers with the database, and Structured Query Language(SQL) for data query. MSHFlexgrid : Hierarchical Flexgrid control which displays the database Text boxes: data is bound with the respective database for display results Combo boxes: offers possible choice for selection Check boxes: Click for display Command button: To execute the different functions or events allocated. Listbox: To select and display data


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RESULTS AND DISCUSSION

Application portabilityThe whole project, namely the data files (map and tables), program and system files, all

ActiveX controls (MapObjects' and VB's), and VBs Data Dynamic Links (*.dll), arebundled into a distributable package such as a setup program.

This has been possible through the package and deployment tool of Visual Basic 6.0version enterprise (Microsoft Corporation). Therefore the application installation does not

require additional training or resource investment from the users. It is a sort of 'plug-n-

play' tool.The installation is done through the set up file, which when double clicked, will auto

install the files into their respective folders: system and dynamic link files (*.dll) as well

as data files. Further the automatic shortcut installation on the desktop invites the user tostart the application program.

Minimum System requirements for this application installation

Operating system: Windows 95 or windows 98

Memory space: 16 MB RAMFree Hard disk space: 50MB

Microsoft Excel 97Microsoft Access 97

Data files: 5 MB

System & program files: 10 MBTotal disk space for setup: 15 MB

* the size may vary with amount of detail collected, and is expected to increase with time.

Application overviewIt consists of a user-friendly interface, based on WYSIWYG where the user easily moves

across the

different screens, with the help of clickable icons, combo boxes, pull down menus for

dynamicmapping of the area of interest, and eventual hard prints output


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Screens sequence

Screen 1 - Welcome Form

Screen 2 - Choice of factory area


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Screen 3 - Data retrieval from project area locality sub-blocks

Screen 4 - Data analysis


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Screen 5 - Spatial query

Advantages of such development1. Minimum IT investment. The existing desktop environment: Windows and Microsoft

Office package is sufficient.

2. A minimum GIS tool is made available, through screen navigation for visual and / orhard prints output. No training is required.

3. No disruption of existing practice. The users may continue with their usual data entry

and update with the standard office packages like Excel, or Access, or in simple relational

database like Dbase as these components are embedded in the application.4. Minimum developers intervention.5. Participation of extension officers in their GIS needs.

6. The ease of information retrieval facilitates decision-making at all levels (field officers,management)

Constraints encountered

1. Incomplete descriptive data sets on farmers records caused delays in data matching.2. Mismatching of field plans with records from the descriptive files.

3. Availability of updated field plans. This implies more ground truthing, and longer time

lag to compile and to finalise the spatial data. Conversion of field plan to spatial digital

file is still onerous. Sale of updated digital files by the Ministry Of Housing and Lands at

a competitive price on the market will give a definite boost to application development ofthis kind.


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Future development

1. Possibility to link different years data with the map files of the same factory area.2. Possibility of file editing(both map, and data) through customised menus / buttons e.g

editing of fields viz., deleting, merging and adding fields as shape files.

3. Extension of the project on a national scale through plug-ins of remaining map files

andrelated data files of all FSCs.4. Privileged Internet access (Brandon 1997) for FSC officers for data analysis.

CONCLUSIONThis new paradigm of GIS moving to an open platform, where it is an equal component

with other third party software, brings new avenues to common users, and application

developers. The GIS products become more affordable, when no more confined to theexclusive environment of professional GIS software, which is usually quite costly, and

requires training and skills.

This application development is but an example of the infinite technical possibilities of

GIS applications, brought about by this breakthrough.

REFERENCES

AITKEN, GP. 1998. Visual Basic 6 Programming. Blue Book Fast-Paced Learning.Coriolis

Technology Press. pp. 700.

BRANDON, P. 1997. GIS Online: information retrieval, mapping, and the Internet.Onward Press. pp

311.

ENVIRONMENTAL SYSTEMS RESEARCH INSTITUTE. 1999. MapObjects V.2.0

Technicalbrochure. pp4. http://www.esri.com/software/mapobjects/description.htm

HARTMAN, R. 1997. Focus on GIS component software. Featuring ESRI's Map

Objects. Onword Press. pp. 340

MICROSOFT CORPORATION. 1996. Microsoft Visual Basic 6.0. Programmer's GuideWashington: Microsoft Corporation. pp. 1000.

GLOSSARY

FSC : Farmers Service CentreGIS : Geographic Information System

IT : Information technology

Mo: MapObjects

OCX : ActiveX Components Objects

Shape files are simple, non-topological format for storing the geometric location and

attributeinformation of geographic features.

SQL: Structured Query Language

VB : Visual Basic

WYSIWYG : What You See Is What You Get


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An Approach to Interactive Social Network

Geo-MappingIIT.SRC 2010, Bratislava, April 21, 2010, pp. 18.

An Approach to Interactive Social Network

Geo-MappingAnton BENI, Roman MSZRO, Roman PANENKA, Mrius AJGALK *Slovak University of Technology

Faculty of Informatics and Information Technologies

Ilkoviova 3, 842 16 Bratislava, [email protected]

Abstract. People nowadays have too many useful items, which they find useless. Thispaper presents a concept of helping people to recycle these items by giving and lending

these items. It is based on map interface and presenting information about other users and

items in system via its geographical location. Data are evaluated base on cooperation withexisting social network and it does not have any need to build up its own social network.

The system uses web services to provide information from the server. It operates as a web

application as well as a mobile application.

1 Introduction

There are many social networks spread around the world nowadays. Visualization of

these networks represent often complicated graphs that are hard to read. Other

solutions use text interface. We decided to provide a map interface support for social

networks visualization. Our solution is aimed on graphical representation of social

networks. To illustrate this idea we have built a system for lending and giving old and

useless items. We use external social networks to be visualized on the map, so we do

not build our own social network but we use item-giving and item-lending data as our

own social network.

To express ideas about geographical mapping of social networks in cooperation

with evaluation system we developed system called Save.

The core part of Save is geographical map of the real world. This map is used to

visualize all the things and people necessary. But we cannot show the user all the

things and people on the map, because it might be chaotic, so we also developed our

* Bachelor degree study programmer in field: Informatics Supervisor: Professor Mria

Bielikov, Institute of Informatics and Software Engineering,

Faculty of Informatics and Information Technologies STU in Bratislava


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Own evaluating system that will sort out people and things due to the current usersactivities. We do not have only static data on the map, because giving and lending

items is activity where an item is moved between two points and we decided to

visualize this. As well as visualizing single transfer we show stories of the items,

where a user can see how many people wanted that thing and they can see its evaluation.Save aims to have as many people as possible and to empower that idea we use

external social networks, where the information about Save and information from Save

are spread. Social networks are also used for people to compete and to motivate them

to use the system. People can see also some of the activities of their friends and many

users find that interesting.

2 User Interface

The user interface consists of four main parts:

- the top control panel,

- side tab panels,- window interface,

- and the map.

The top control panel provides the user with basic information, such as which accounts

are connected or whether there was anything new of an interest to him since his last

visit. The side tab panels provide the user with access to the most common

functionality, while the window system is used to show the more detailed content.

While none of the three mentioned parts are meant to be dominant the map is

supposed to be the main navigation control. The map has two view levels. First one is

the static view, where the user can choose between showing the people or the items. Inboth people and items view, the user can consequently navigate through items and their

owners by pointing and clicking the mouse over the dynamic content that appears as

the user navigates. This view level uses IntelliView, which is a map content management

algorithm and will be discussed in the following section.

The second level adds dynamics to the map, by displaying the activity of others.

This activity is shown on top of the static view, be it either people or items, while the

IntelliView algorithm takes care of freeing space on the map and appropriate

positioning of the animation. This level can be used to show either the past activity to

visually inform the user of what has happened since his last visit or the activity in near

real-time using RealView, which is described in the section five


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3 IntelliView

Basic concept of presentation is to visualize as many information as possible on map

[1,2]. Map is intended to serve as an information presenter for displaying friend lists,

search results, history logs, routes, etc. In order to fulfil these requirements, IntelliView

An Approach to Interactive Social Network Geo-Mapping 3

Provides set of functions, which manage visualization. Besides geo coding, that is

inevitable to find specific location, main stress is laid in choosing and organizing

elements on map.

Due to enormous number of items to be displayed, IntelliView must choose only

some subset of these items in order to maintain lucid view. To accomplish this, items

are sorted by priority. Priority is defined as single number and its computation varies

with type of item, which is described later asItem evaluation in more details.

Prioritization as well as some other principles, which are mentioned later, is based onmost common visualization techniques that can be found in Bing Maps, Google maps,

and also in well-known ESRIs geographic information system (GIS) softwareproducts.

With list of items sorted by priority, IntelliView aims to achieve following basic

goals:

display as many information as possible, display items with higher priority first, illustrate density of items, maintain simplicity of view.

We proposed two main methods for displaying items, each of them with its own pros

and cons. First, probably most intuitive method is depicted on Figure 1 and Figure 2.

Items are iterated over by their priority and every time there is a check, if there is a

collision. If not, the item is displayed. If there is a collision, the item is considered to

be displayed with less importance and in order not to overlay those already displayed

(which have evidently higher priority), their size is reduced and opacity decreased.

Ordered by importance, they are grouped into several levels of importance. Visually,

displayed items differ based on level, which they are included in. To maintain lucid

view, items distribution is pushed to the last level, which is not displayed. Thus, visual

differences among levels can be less significant. Presence of hidden items in the lastlevel is represented by background colour of appropriate topmost item. In this manner,

density can be viewed as well. Advantage of this method is accurate projection of item

location, but considering priority order, items in higher levels can have lower priority

than those in lower levels.


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Figure 1. IntelliView in action


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Figure 2. IntelliView in action

Second method tries to achieve greater accuracy of displaying priority by dividing

whole viewport into grid and considering items isolated, individually in each cell.

Thus, each cell has its own representative, which is dominating in the centre of this

cell. Items in lower levels of importance are displayed similarly as in preceding method

around cell's representative. While having improved accuracy of priority order depiction,

this method has also better performance in calculation following principles of divide and

conquers.

However, in this case, location of item cannot be determined due to error caused

by centralization within cell. The goal of centralization is to avoid collision problems

on neighbouring cell's bounds. As a positive side effect, due to uniform distribution of

items on the map, this view is symmetric and more readable, too.


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4 RealView

The integration of social networks and the visual representation have the purpose to

make the system attractive and alive over time. RealView brings the activity to the end

users by showing them actions performed by others in near real time. The RealView

algorithm processes actions that other users perform within the viewing area and displays

them as animations on the map.

The algorithm could just show all or at least majority of the actions, but it would

not be practical for a couple of reasons. First of all with rising number of actions, the

traffic is rising too. Second, the purpose of this dynamic view is to bring the user activity

to encourage him to be active as well, but overwhelming him with animations

would rather be counterproductive. That is why we implemented a filtering system,

whose purpose is to select which actions will be delivered to the individual users.

The decision process is time sensitive and is based on a modified version of the

relevancy system that is used in IntelliView.

The time sensitivity means that despite of not showing all of the actions in the viewingarea, the algorithm still has to be aware of the rate at which the actions happen. When

implementing the mentioned features, we cannot work in true real-time. The basic idea is

to stack the animations in a list, putting a delay interval between them that reflects theactivity rate.

We briefly introduce two specific implementations of this concept. The first

algorithm maintains an ordered list of actions and the number of actions from the last

animation. Then every time a given number of actions are processed, it picks the first

one and displays its animation.

The ordering is performed in a following way:

when an action is intercepted, its relevancy value is calculated, all actions with lower relevancy are dismissed from the list, the processed action is added to the end of the list.

This ensures that the first action in the list has always the highest relevancy and that we

keep all consequent animations.

The second algorithm is a simplification of the first one. It stores only one, most

relevant action and the number of actions from the last animation. Then every time a

given number of actions were processed it displays the stored animation.


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5 Social networks

The system does not build its own social network, it uses external networks of

Facebook, Live or Twitter. On the other hand, we maintain our own action-built

network. In this network users are connected by its same interest in some sort of things.

To provide recommendations, we use keywords of the current item and its synonyms.

Users and items are also user-evaluated.Currently, we aim our main focus to the biggest social networkFacebook. Sinceour system is designed to be open to other social networks, it is easy to integrate them

in the future and to extend system availability. Integration of social network is twoway.

The user can authenticate with his social network credentials and use our system

with the same friends. But on the other hand there is sort of integration to his Facebook

account. Our system provides triggered updates to user's wall including photos of

things he has provided, things he has borrowed or lent, and events he has done etc. and

regular updates with user statistics, social impact information and posts about

successful stories. All these updates are controlled and adjustable, to lower the measure

of spam.In addition to common statistics of the user activity, there are statistics provided

by user geographical location. They include amount of welfare done in his location,

statistics of users from his neighborhood and especially comparison with neighboring

regions and countries. This indirectly leads to geo competition and bigger interest in

our system.

6 Save the system for recycling items in social networks

The system core was designed as a WCF (Windows Communication Foundation) web

service that can be used by different clients to provide functionality to the end user(see

6 Roman Mszro et al.

Figure 3). The client list consists of a Silverlight application that provides most of the

system core functionality, a mobile application that is intended for quick access to

some of the main functions and a Windows gadget that will just inform the user of

various events in the system. Since the functionality is fully in hands of a web service,

the system is open for new clients. The only thing that the client is required to

imlement is the authentication process, briefly described below.

To simplify the registration and authentication process and to make it more

attractive for a new user to join the community as well, we have optioned for a login

system, where the user can use his existing account form other web service to

authenticate himself. Since our aim is to encourage people to help and we intent to

promote this help through currently most intensive services - social networks, we have

chosen Facebook and Twitter service to provide this autentication. This base can be

further extended in the future. The process of authentication mostly involves the client

application that takes care of acquiring the valid session keys from the credentials

provider and provides them to the service core.


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Figure 3.System architecture

6.1 Web services

The system uses service-oriented architecture [3] using Windows Communication

Foundation. This way client can abstract from the functionality that is provided by

server. Using web services avoids client from manipulating with data directly, because

the connection to the database is provided by them. Because business logic is moved

into one place (server), it is far easier to modify that code only once. It also provides

the interface that can be used by plenty of applications. Our system is both a web-based

application and a mobile application and it is also integrated into Facebook by editingits source code via proxy or the web browser, but the business logic itself is contained

into web services used.

6.2 System extensions

Users are informed about recent news without being on system web site also. They can

use add-ons to various browsers, widgets on operating system desktops or install small

applications to their mobile phones. In all these extensions there is provided lower

functionality with basic but significant information. More complicated tasks are

redirected to main web application.

When a user uses our browser add-on, communication with the server isredirected through our proxy server. The proxy server augments our system integration

to the Facebook. More relevant information can be seen, better information structure

can be seen and better Facebook layout is provided.


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6.3 Item Evaluating

Our system works with many items and many users with different point of interest.

Apart from standard searching for items, the system has to provide ordering of items,

which is based on interests and categories of current user and also similar users,

evaluation of items in system and evaluation and score of the user, which wants or

offers the item.First of all we aim on the point of interest [5] of the current user. We check his

activity in the system and things he get or gave the system recommends items from the

same item category, parent category or the system finds items based on key words and

words connected using synonymic dictionary. This is performed by Spreading

activation algorithm [6] with the current user or any of his items as source and we

spread the initial energy from there.

Second of all is looking for similar users [5]. Similar user is the user, who looks

for the same categories of things and searches for the same keywords. Based on the

similar user, we assume that things wanted by the similar user might be wanted by

current user also. We used HITS algorithm [7] assuming the current user. Therefore theitems he references are assumed to be trustful as well. Next we find a user that references

these trustful items and we consider him trustful also and then we recommend the current

user the items, other trusted users referenced.

After checking for similar user we filter items based on the items evaluation by other users. Every user is free to evaluate items offered by other users. They can evaluate

these items by number, which is used for the purpose of the system, and by comment,

which is far more useful for other users to communicate. Items are evaluated by usersrating and they are also evaluated by number of visitors. These states are handled by

PageRank algorithm that assumes, that the item or user is that better that more times it is

referenced [8].

The last part is to order these items by the offering or wanting users evaluation by other system users and by his activities done in system. Users that have betterevaluation are more competent and responsible and items provided by them will be

sorted before irresponsible users with miserable evaluation.

VII. Conclusion

This paper presents new modern ways of presenting information from social network

via map interface. Our system demonstrates usage of this information in cooperation

with giving subsystem. That concept can be easily changed to track some other

information connected to these users.

This paper also described our system that is used as a mediator between users, one donor

and another one, acceptor. The system aims on solving problem of recycling items

making them cycle again and not just go to trash and it aims on helping people in

need as well. The system is also designed to provide lending service between users a

tracing the items given and lent.


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Acknowledgement: This project was supported by Faculty of Informatics and

Information Technology as Imagine Cup 2010 Software design category project.

This work was partially supported by the Cultural and Educational Grant Agency of

the Slovak Republic, grant No. KEGA 028-025STU-4/2010.

References

[1] Gibbon, D. et al.: GeoTracker: Geospatial and Temporal RSS Navigation. In:

Proc. ofWWW 2007, ACM Press, (2007), Banff, Canada, pp. 4150.[2] MacEachren, Alan M.: How maps work: representation, visualization, and

design. The Guilford Press, (2004).

[3] Datz, T.: What you need to know about service-oriented architecture. CIO,

(2004).

[4] Barla, M.,Bielikov, M.:Wild web personalization: adaptive proxy server. In:

Proc. Of 4th Workshop on Intelligent and Knowledge oriented Technologies,Herany, Slovakia, (2009), pp. 48-51(in Slovak)[5] Chawla, A. et al.: Group Recommendation: Semantics and Efficiency. In: Proc.

of VLDB 2009, ACM Press, (2009), pp. 754765.[6] Crestani F.: Application of spreading activation techniques in information

retrieval. In: Artif. Intell. Rev., Springer, (2004),pp. 453482.[7] Liu, B.: Web Data Mining: Exploring Hyperlinks, Contents, and Usage Data

(Data-Centric Systems and Applications). Springer-Verlag, New York, NJ, USA,

(2006).

[8] Page, L., Brin, S., Motwani, R., Winograd T.: The PageRank citation ranking:

Bringing order to the web. In: Proc. of the 7th International World Wide Web

Conference, Brisbane, Australia, (1998), pp. 161172.


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Map Control Using Visual Basic

In this introductory document you will use the ESRI Map control andMicrosoft Visual Basic to build an application that uses maps. Along the way you will

learn how to

Display a map with multiple layers.

Control panning and zooming. Create a Toolbar control. Display map layers based on scale. Perform spatial and logical queries. Draw simple graphics on the map. Display features with thematic renderers. Dynamically display real-time event tracking. Programmatically add data to a map. Add Identify and Query commands from the sample AfCommandsVB library.

Loading the Map controlStart Visual Basic and select New project from the dialog

box. Select Components from the Project menu or press

Ctrl+T.

Find ESRI ArcObjects Controls 8.1 in the list of availablecontrols and check the box beside it. Click OK to close the

dialog. Notice that a new tool appears in the Visual BasicToolbox. This new tool is the ArcObjects Controls Version 8.1 Map control


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Getting help

The Map control is an ActiveX control that is provided byESRI as part of the ArcObjects development toolkit.

To find out about the available methods, properties, and

events that are provided with the Map control, click the

Object Browser button in the Visual Basic toolbar (or hit F2). Pull down theProject/Library boxand chooseesriControlsCtl.

The esriControls objects and constants are listed in the

Classes bottom left-hand list.

Click on the Map control object in the list, and its propertiesand methods are listed in the Members list to the right.

Likewise, click on a method in the right-hand list to see the method signature. The details

will appear in the space at thebottom of the Object Browser.

The ArcObjects online help system is also integrated withthe Visual Basic Object Browser.

1. Click MapControl in the Classes/Modules list.2. Click VisibleRegion in the Methods/Properties list.

3. Click the help (question mark) button.


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Adding the ESRI Object Library

To fully access all available ArcObjects components in yourVisual Basic project, you will need to add a Reference to

the ESRI Object Library to your project. To do this, pull down the Project menu and selectReferences. Find and check ESRI Object Library in the list of available references.

Again, from within the Object Browser, you can see all the available objects and components in

ArcObjects by

selecting esriCore from the Project/Library box.


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Using the Map control

The Map control allows you to load map data from a variety of data sources including

ArcSDE layers, ArcInfo coverages, shapefiles, and raster files. You can also loadArcMap documents (*.mxd) into your Map control. Loading an ArcMap document into the Map control will add each of the referenced layers into the control, complete with

saved definitions such as extents and renderers. You can also load individual layer files(*.lyr) in this way.

The Map control also provides you with a number of helper methods such asTrackRectangle and AddLayer. We shall use some of these as we progress through this

book. The Map control also has properties that expose references to the internal interfaces

used by the Map control such as the IMap, IActiveView, and ILayer interfaces. Usingthese properties will give you a hook into the rich functionality available within theArcObjects Object Model.

Add the Map control to the form

1. Double-click the MapControl button in the toolbox to add anew map to the form.

2. Resize the map to fill the form.


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Select the data to display on the map

You can specify the data that is displayed on the map by

setting properties in the MapControls Property Page.1. Right-click the mouse on the map to display the context

menu.

2. Choose Properties to display the Property Pages.3. Click the Add button and locate the folder containing the

states sample data.

4. Click the states.shp file and then click Add.5. Add the file ushigh.shp in the same manner.

6. Use the Up and Down arrows to ensure that the ushigh layer

is at the top of the list.

You can also specify how the data is displayed on the Map

by using this Property Page.


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Set properties for the layers

1. Click the ushigh layer in the Layers list and then click Properties.2. Modify the ushigh layer symbology: Click on the Symbology tab. Click the Symbol

button. Select a red color and click OK to dismiss the Layer Properties dialog.

3. Now define a renderer for the States layer: Select States from the list of layers. Click

on the Symbology tab.In the Symbology tab select Categories and then click on Unique values.

Make SUB_REGION the Value field and click on the Add AllValues button.

You can double-click on the colors to display the Colordialog box.

4. Click OK to close the Property Page.

Save the project1. Click the File menu and then click Save Project.

2. Browse to a suitable folder, then in the File Name box type StarterMap.frm.

3. Click Save.4. In the second Save dialog, type StarterMap.vbp in the File Name box.

5. Click Save.

Test your application1. Click the Run button in the Visual Basic toolbar.

2. To stop running your application and return to design mode,

click the Stop button in the Visual Basic toolbar.


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Adding pan and zoom controls

At this point your application can display the map at its fullextent. In this section you will add some simple pan and

zoom controls that your application will activate in response

to mouse clicks inside the map. You will write some code

that the application will execute in response to theOnMouseDown event on the map.

Respond to the MouseDown event1. Double-click on the Map control to display the Visual Basic

code window.

2. Add code to MapControl1s OnMouseDown procedure.Private Sub MapControl1_OnMouseDown(

ByVal button As Long, _

ByVal shift As Long, _

ByVal x As Long, _

ByVal y As Long, _ByVal mapX As Double, _

ByVal mapY As Double)

MapControl1.Extent = _ MapControl1.TrackRectangle

End Sub

TrackRectangle is a method that applies to the Map control. It tracks the movement of themouse while the user keeps the mouse button pressed, rubber-banding a rectangle at thesame time. When the user releases the mouse button, the TrackRectangle method returns

an IEnvelope object that the application then assigns to the Extent property of the map,

causing the map to be redrawn with a new map extent.

Test your change

1. Click the Run button in the Visual Basic toolbar.2. Click the map with the left mouse button and drag out a

rectangle.


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3. Release the mouse button and notice that the map is

redrawn at the location you specified.4. Click the Stop button in Visual Basic to return to design

mode.

Add panning1. Double-click the map to display the Visual Basic code

window again.

2. Change the code for the OnMouseDown event.

Private Sub MapControl1_OnMouseDown(

ByVal button As Long, _

ByVal shift As Long, _

ByVal x As Long, _

ByVal y As Long, _

ByVal mapX As Double, _

ByVal mapY As Double)

If Button = vbLeftButton Then

MapControl1.Extent = _

MapControl1.TrackRectangle

ElseIf Button = vbRightButton Then

MapControl1.Pan

End If

End Sub

If the Button parameter is equal to vbLeftButton when the

OnMouseDown event occurs, then the zooming code from

the previous step will be executed. Otherwise, the code will

call another Map control method, Pan. If the user clicks theleft mouse button, the Button parameter will be

vbLeftButton. If the user clicks the right mouse button, the

value of Button will be vbRightButton.

Add a FullExtent button

Your application now supports panning and zooming but,once the user has zoomed into the map, there is no way to

get back to the full extent again. In this section you will add

a button to the form that zooms the map to the full extent.

1. Double-click the CommandButton button in the Toolbox to

add a button to the form.2. Move the button to the upper right of the form.

3. Press F4 to display the Properties window.

4. Click in the Caption box and type Full Extent to change the

buttons caption.


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5. Resize the Map control so that it is not obscured by the button.

6. Double-click the Full Extent button to display the code window.

7. Add code for the Click event.

Private Sub Command1_Click()

MapControl1.Extent = MapControl1.FullExtent

End Sub8. Finally, when you are in Design mode, use the Visual Basic Properties box to change

two properties of the Map controlset ShowScrollBars to False and choose a color forMapControls BackColor property.The FullExtent property of the Map returns a reference to an IEnvelope that defines the

bounding box ofall the layers in the Map.

Test your change1. Click the Run button in the Visual Basic toolbar.

2. Click the map with the left mouse button and drag out a rectangle.

3. Release the mouse button to redraw the map.

4. Click the map with the right mouse button and drag to pan the map.5. Release the mouse button to redraw the map.

6. Click the Full Extent button to redraw the map at the full extent.

Save the project1. Click the Stop button in the Visual Basic toolbar to return to

design mode.2. Click the Save Project button in the Visual Basic toolbar to

save your changes.

Adding a toolbar

Visual Basic includes a Toolbar control that can be used inconjunction with an ImageList control to display a collection of buttons at the top of a

form. We shall use the Visual Basic Toolbar for this starter application. The current

applications pan and zoom functionality is somewhat hidden from the user. In thissection, you will create a toolbar with Pan and Zoom buttons.


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Adding a toolbar

1. Delete the Full Extent button from the form.2. Bring up the Components dialog by pressing Ctrl+T. Select

Microsoft Windows Common Controls. You will notice new

tools are added to your toolbox.

3. Double-click the Toolbar button in the toolbox to add aToolbar control to the form.

4. Double-click the ImageList button in the toolbox to add an

ImageList control to the form.5. Resize the map so that it is not obscured by the toolbar.

The ImageList control may obscure the map; however, thisis not a problem because the ImageList control will not be

visible when your application is running.

Adding images to the ImageList control

1. Right-click the ImageList control to display the context menu.

2. Click Properties to display the Property Pages.3. Click the Images tab.

4. Click Insert Picture and locate the folder that contains the sample bitmaps. This should

be the Icons directory within the ArcGIS Bin folder.

5. Click the zoom_in_tool_1.bmp file and then click Open.6. Add a descriptive Key, for example, Zoom. This will correspond with Keys that willbe used when adding buttons to the Toolbar control.


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7. Add the files pan_1.bmp, globe_3.bmp, select_by_polygon.bmp, flag.bmp,

information.bmp, and selection_1.bmp in the same manner. The Keys should be

FullExtent, SelectByPolygon, TrackEvent, Identify, and Query, respectively.

Set the MaskColor of the ImageList

Setting the MaskColor property of an ImageList control specifies a color that will act as amask for any images contained by the control. The mask color will not be drawn,

resulting in an image with a transparent background.

1. Click the Color tab.2. In the Properties list, click MaskColor.

3. Click Magenta in the Color Palette list and then click OK todismiss the Property Pages.

Associate the ImageList with the toolbarYou can associate the Toolbar control with an ImageList

control to provide the graphic images for the buttons.

1. Right-click the Toolbar control to display the context menu

2. Click Properties to display the Property Pages.

3. In the ImageList box, click the arrow and then click ImageList1. This associates thetoolbar with the ImageList control.


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Adding buttons to the Toolbar control

In this section you will add seven buttons to the toolbar.1. In the Toolbar Control Properties dialog, click the Buttons tab, then click Insert Button.

2. Set the buttons style to ButtonGroup, its Image to Zoom, itsKey to Zoom, and itsValue to Pressed. Add suitable Tool Tips.

3. Add a second button and set its Style to ButtonGroup, its Image to 2, and its Key toPan.4. Add five more buttons and associate them with the remaining images in the ImageList,

setting their Style to ButtonGroup (add Separators if you wish). The Keys should beFullExtent, SelectByPolygon, TrackEvent, Identify, andQuery, respectively.5. Click OK to dismiss the Property Pages

Change the OnMouseDown event1. Double-click the map to display the Visual Basic code window.

2. Completely replace the code in the MapControl1s OnMouseDown event handler withthe following:

With Toolbar1.Buttons

If .Item("Zoom").Value = tbrPressed ThenMapControl1.Extent = MapControl1.TrackRectangle

ElseIf .Item("Pan").Value = tbrPressed Then

MapControl1.Pan

End If

End WithSelecting the first button in the toolbar sets the mouse to be

a zoom tool; selecting the second button lets you use themouse to pan.


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The Toolbar ButtonClick Event Handler

In this section you will implement the handler for theButtonClick event that is generated whenever a click

occurs on a button in the toolbar.

We will add code to change the MapControls

MousePointer depending on what tool has been selected,providing useful feedback to the user. We shall also

reimplement the Full Extent button that you deleted. Within the event handler we will be

using a Case statementwith switches, depending on the Key value of the button

that you defined earlier.

1. Double-click the toolbar to display the code window.2. Add the following code to Toolbar1s ButtonClick event.Private Sub Toolbar1_ButtonClick(ByVal Button _

As MSComCtlLib.Button)

With MapControl1

Select Case Button.KeyCase "Zoom"

.MousePointer = esriPointerZoomIn

Case "Pan"

.MousePointer = esriPointerPan

Case "FullExtent"

.MousePointer = esriPointerDefault

.Extent = MapControl1.FullExtent

End Select

End With

End Sub

Test and save your changes

1. Click the Run button in the Visual Basic toolbar.2. Drag a rectangle to zoom in.

3. Click the pan button in your applications toolbar.

4. Click somewhere on the map and then drag to pan.

5. Click on the Full Extent button (the globe) in your applications toolbar.


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Creating a find toolIn this section you will add additional controls to yourapplication to implement a simple function for locating a

state by name. Once the State is located you will zoom to it.

Add controls to the form1. Double-click the Label button in the toolbox to add a label to

the form.

2. Reposition the label in the lower left corner of the form.3. Display the Properties window by pressing F4 and set the

caption of the label to be State:.

4. Double-click the TextBox button in the toolbox to add aTextBox to the form and position it next to the label.

5. Clear the Text property of the TextBox using the Properties

window.

6. Resize the map so that it is not obscured by the new controls

Attach code to the TextBox

You will use the text the user types into the TextBox toperform a logical query.

1. Double-click the TextBox to show the code window.

2. Add code to Text1s KeyPress procedure by selectingKeyPress from the right-hand dropdown list:

Private Sub Text1_KeyPress(KeyAscii As Integer)

If KeyAscii = vbKeyReturn Then

' Find the States layer

Dim i As IntegerDim pFeatLyr As IFeatureLayer

For i = 0 To MapControl1.LayerCount - 1

Set pFeatLyr = MapControl1.Layer(i)

If pFeatLyr.Name = "states" Then

' Found it and exit loop

Exit For

End If


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Next i

' Create a string to use in the query

Dim queryStr As String

queryStr = "STATE_NAME = '" & Text1.Text & "'"

' Create the query filter

Dim pQueryFltr As IQueryFilterSet pQueryFltr = New QueryFilter

pQueryFltr.WhereClause = queryStr

' Perform the selection

Dim pFeatSeln As IFeatureSelection

' QI for IFeatureSelection from the

' IFeatureLayer

Set pFeatSeln = pFeatLyr

pFeatSeln.SelectFeatures _

pQueryFltr, esriSelectionResultNew, False

' Get the selection setDim pSelSet As ISelectionSet

Set pSelSet = pFeatSeln.SelectionSet

' Get the cursor from the selection set

Dim pFeatCursor As IFeatureCursor

pSelSet.Search Nothing, True, pFeatCursor

' Assume only one feature

Dim pFeature As IFeature

Set pFeature = pFeatCursor.NextFeature

If Not pFeature Is Nothing Then

' Get the extent of the selected feature

Dim pExtent As IEnvelope

Set pExtent = pFeature.Shape.Envelope

' And set the Map control's extent

MapControl1.Extent = pFeature.Shape.Envelope

End If

End If

End Sub


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1. Run your application.2. Type the name of a state, for example, New Jersey, into the

TextBox.

3. Press the Enter key.

4. When you are finished running your application, click theStop button in the Visual Basic toolbar and Save your

application.

The code locates the States layer and defines a simple SQL query expression using the value of

the Text property of the TextBox. The States layers IFeatureSelection uses this query to searchfor the specified value. You can obtain an IFeatureCursor that contains all features from the

IFeatureSelection. Here we assume the cursor contains only one feature, from which we willderive the geometry and its extent envelope. We will use this envelope to reset the MapControlsExtent.

Handling resize

When you run your application and resize the form, you will

notice that the map is not automatically resized.

Respond to the Resize event1. Double-click the form to display the code window.

2. Add code to the forms Resize procedure by selecting Resize from the right-hand dropdown list:

Private Sub Form_Resize()

If (ScaleWidth 0) Then

' y coord for Text and Label

Dim yFind As Integer

' a constant spacing

Dim space As Integer

space = Text1.Top - (MapControl1.Top _


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+ MapControl1.Height)

yFind = ScaleHeight - Text1.Height - space

' x coord for Text and Label

Dim xFind As Integer

xFind = ScaleWidth - Text1.Width

Dim mapTop As IntegermapTop = Toolbar1.Top + Toolbar1.Height

Dim mapHeight As Integer

mapHeight = yFind - space - mapTop

If (mapHeight > 0) Then

' move all the controls

Text1.Move xFind, yFind

Label1.Move xFind - _

Label1.Width - 20, yFind

MapControl1.Move 0, mapTop, _

ScaleWidth, mapHeight

End IfEnd If

End Sub

3. Double-click the form to show the code window.

4. Add code to the forms Load procedure.

Private Sub Form_Load()

Form_Resize

End Sub


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When the user resizes the form, the code resizes the controls using the Move method.Notice that when you run your application it redraws the map twice initially. This is due

to the fact that controls on the form are initially displayed using the size and position

specified during design time. To fix this problem, you will resize the controls when theform is initialized. You have already written the code to resize the controls, so you just

need to call the procedure.

Test and save your changes1. Run your application. Notice that it does not draw the

Counties layer.

2. Zoom into New England and the Counties layer becomes

3. Click the FullExtent button and the Counties are no longer

visible.

Adding a spatial query toolIn this section you will add a new tool to the toolbar that

performs spatial queries on the map and also add code that

draws the results. We have already added the button to theToolbar, so we just need to add code to implement its

functionality. We will use the SelectByPolygon button, the

fourth button on the toolbar. When the SelectByPolygon

button is clicked, we will handle the OnMouseDown eventdifferently, calling a procedure called SearchShape to

actually peform the spatial selection.


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Implement the SearchShape procedure

Private Sub SearchShape()

Dim pSearchShape As IPolygon

' Create the search shape

Set pSearchShape = MapControl1.TrackPolygon' Do the actual selection

With MapControl1

.Map.ClearSelection

.Refresh esriViewGeoSelection

.Map.SelectByShape pSearchShape, Nothing, False

' And refresh the map.Refresh esriViewGeoSelection

End With

End Sub

Call the SearchShape procedure1. Modify MapControl1s OnMouseDown procedure and insertthe following:ElseIf .Item("SelectByPolygon").Value =_

tbrPressed Then

SearchShape2. Finally, modify the Toolbar_ButtonClick procedure to change

the MapControls Mousepointer.Case "SelectByPolygon"

.MousePointer = esriPointerCrosshair

Test and save your changes1. Run your application and zoom into an area so that the Counties layer becomes visible.

2. Click the spatial query tool, then digitize a polygon. Doubleclick to end. You should

see that counties that intersect with the polygon are highlighted. Optionally, from theProperty Pages, display the Layer

Properties dialog to modify the default Selection Symbol for

each layer. Set it to a yellow solid fill.


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Event tracking

Some applications must display geographic entities on top of the map, especially if thoseentities have a tendency to move.

For example, a vehicle tracking system would want to display vehicles on the map at the

appropriate locations and update those locations over time without redrawing all the

underlying layers of the map each time a vehicle changes location.In this section, you will add event tracking layer elements to your application to facilitate

this requirement. We have already added the required toolbar button (the Flag at toolbar

button number five), and now we shall implement the tool.

Implement the Event tool

1. Add a private member variable to the General section of the Forms code window.This will be an ElementCollection that will be used to hold your events.

Private m_pElementCollection As IElementCollection

2. In the Form_Load method, initialize the collection: Set m_pElementCollection = New

ElementCollection

3. Modify the Toolbar1_ButtonClick procedure to change the MapControlsMousepointer. Case "TrackEvent"MapControl1.MousePointer = esriPointerHotLink

4. Modify the MapControl1s OnMouseDown procedure to call AddGeoEvent, passing inthe mapX and mapY coordinates.

These are already in Map units.ElseIf .Item("TrackEvent").Value = tbrPressed Then

AddGeoEvent mapX, mapY

Implement the AddGeoEvent procedureThe AddGeoEvent procedure adds a new element where

the mouse click occurred. Add the following code to the

General section of the Forms code window.

Private Sub AddGeoEvent(mapX As Double, mapY As Double)

' Make the point

Dim pPoint As IPointSet pPoint = New Point

pPoint.PutCoords mapX, mapY

' Make the elementDim pElement As IElement

Set pElement = New MarkerElement

pElement.Geometry = pPoint

' Add the element to the collectionm_pElementCollection.Add pElement

' And finally redraw the map

MapControl1.Refresh esriViewForegroundEnd Sub


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Drawing the events

After the layers draw, we iterate through the collection of

events to draw each, in turn, using the MapControlsDrawShape method. Add this code to the OnAfterDraw

Event procedure.

Private Sub MapControl1_OnAfterDraw(ByVal display AsesriCore.IDisplay, ByVal phase As

esriCore.esriViewDrawPhase)

If (phase = esriViewForeground) ThenDim pElement As IElement

Dim i As Integer

For i = 0 To m_pElementCollection.Count - 1m_pElementCollection.QueryItem i, pElement

MapControl1.DrawShape pElement.Geometry

Next

End If

End Sub

Test and save the Event tool1. Run your application.

2. Zoom into an area.

3. Click the event tool, then click in the map to add events.4. Click the Stop button on the Visual Basic toolbar and save

your project.

Add a timer to your formTo trigger the movement of the events, a Timer control will

be used. The Visual Basic function Rnd is used togenerate a random number to move the events in a random

manner.1. Double-click the Timer button in the toolbox to add a timer to

the form. The Timer control will not be visible when your

application is running.2. Double-click the timer to display the code window.

3. Add code to the timer procedure.

Private Sub Timer1_Timer()

Dim maxDist As Double

Dim nEventCount As Integer

Dim pt As IPointmaxDist = MapControl1.Extent.Width / 20

nEventCount = m_pElementCollection.Count

Dim newX As DoubleDim newY As Double

Dim i As Integer

' If the collection is not empty


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If (nEventCount > 0) Then

Dim pGeometry As IPointDim pElement As IElement

' Iterate the collection

For i = 0 To nEventCount - 1

m_pElementColn.QueryItem i, pElementSet pGeometry = pElement.Geometry

' Generate a new random position

newX = pGeometry.x - (maxDist * (Rnd - 0.5))newY = pGeometry.y - (maxDist * (Rnd - 0.5))

' And update the element

pGeometry.PutCoords newX, newYpElement.Geometry = pGeometry

Next i

MapControl1.Refresh esriViewForeground

End If

End Sub

Add a CheckBox to your formTo turn the timer on or off, you will add a CheckBox control

to your application.

1. Double-click the CheckBox button in the toolbox to add aCheckBox to the form.

2. Move the CheckBox to the lower left corner of the form.

3. Open the Properties window and set the Caption to DataCollection.4. Double-click the CheckBox control to open the code window.

5. Add code to Check1s Click procedure.Private Sub Check1_Click()

Timer1.Interval = Check1.Value * 500End Sub

Modify Form_ResizeModify the Form_Resize method to move the CheckBox when the form is resized. Just

before the Text1 and Label1 controls are moved, insert the code for moving the Check1

control.' Move all the controls

Check1.Move 0, yFind

Text1.Move xFind, yFind

Test your changes1. Run your application.

2. Zoom into an area.

3. Click the event tool, then click in the map to add events.4. Click the Data collection check box. Notice that the events

start moving randomly on top of the map.

5. Click the check box again to stop the events.


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Adding layers programmaticallyIn each of the previous sections, you have worked with Layer objects that were specified

interactively using the MapControls Property Pages. In this section, you will add code toyour application that creates Layer objects programmatically. There are a number ofmethods that you can use to programmatically add layers to your Map control:

LoadMxFileThis method will load an ArcMap document (an MXD file). If theArcMap document contains multiple maps, then it is possible to state which one you want

to load by passing in an index. Each map can contain multiple layers, and all layer

properties (such as renderers) will be retained. Note that if you want to use an ArcMap

document to add layers to your Map control, then this method should be called before anyadditional layers are added.

AddLayerFromFileUsing this method you can add a layer that has previously beensaved to a layer file (lyr). You can also optionally specify an index to force the new

layers position within currently loaded layers. All symbology for the layer that wasdefined within ArcMap is also honored within the Map control.

AddShapeFileThis method allows you to add shapefiles by specifying the path and the

shapefile name. The new layer is added on top of any previously loaded layers. Default

symbology is provided by ArcObjects.

AddLayerThis method takes as parameters a reference to an ILayer and an optionalindex value. This allows you to create and load layers that come from different data

formatsfor example, Coverages, TIN, Raster, or ArcSDE. See theArcObjectsDevelopers online reference, theExploringArcObjects book, or theArcObjects Class

Help online for further details on creating layers.


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The example code that follows loads three layers using two of the above methods. Ensure

that you change the paths to the data to match your installation.

Remove the existing layers

1. Right-click the mouse on the map to display the context menu.

2. Choose Properties to display the Property Pages.3. Click on the ushigh layer, then click Delete to remove the layer.

4. Remove counties and states in the same manner, then click OK.

Add a procedure that will initialize the map1. Double-click the form to display the code window.

2. In the General section, declare a procedure.

Sub InitializeMap()

' Change the paths to reflect your installation

Dim pFactory As IWorkspaceFactory

Dim pWorkspace As IFeatureWorkspaceDim pFeatLayer As IFeatureLayer

' Create a new ShapefileWorkspaceFactory objectSet pFactory = New ShapefileWorkspaceFactory

Set pWorkspace = pFactory.OpenFromFile("C:\Data\USA", 0)

' Create a new FeatureLayer and assign a shapefile to itSet pFeatLayer = New FeatureLayer

Set pFeatLayer.FeatureClass =

pWorkspace.OpenFeatureClass("States")

pFeatLayer.Name = pFeatLayer.FeatureClass.AliasName' Add the FeatureLayer to the map

With MapControl1

.AddLayer pFeatLayer

.AddShapeFile "C:\Data\USA", "counties

.AddShapeFile "C:\Data\USA", "USHigh"

End With

End Sub


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Modify the Form_Load procedure

1. Immediately after the call to Form_Resize and before the section of code that sets theminimum and maximum display scales for the layers, insert the following line:

InitializeMap

2. To ensure that the MapControls MousePointer correctly reflects the startup status of

the Toolbar, insert the following line after the call to InitializeMap:MapControl1.MousePointer = esriPointerZoomIn


1. Run your application. The map should appear as before, but default colors andrenderers are used and therefore may be different than the colors you previously selected

in the Layer Properties dialog box.

2. Click the Stop button in the Visual Basic toolbar and save your project. Working withRasterLayer objects In each of the previous sections, you worked with MapLayer objects

based on vector data sources. In this section, you will see how to add layers to your map

that are based on images. ArcObjects allows you to use a wide range of image types as

RasterLayers including such common image types as windows bitmaps (.bmp), tagged

image file format (.tiff), and CompuServe bitmaps (.gif).

Select an image layer to display on the mapYou can specify an image to display as a RasterLayer by setting properties in the

MapControls Property Pages.1. Right-click the mouse on the map to display the context menu.2. Choose Properties to display the Property Pages.

3. Click the Add button and then select Raster datasets from the Show of type combobox.

4. Navigate to a data folder that contains raster datasets. If you have the ESRI Data &Maps CD, you can use the sample image wsiearth.tif.5. Click on the raster dataset file, then click Add.

6. If you still have other datasets listed in your Property Pages, use the arrow buttons to

ensure that the raster data is at the bottom of the list.

Test your changes1. Click the Run button in the Visual Basic toolbar.

2. To stop running your application and return to design mode,click the Stop button on the Visual Basic toolbar.


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Adding a RasterLayer programmatically

Previously, you added feature layers programmatically; now you will add a RasterLayerprogrammatically.

Remove the existing layers

1. Right-click the mouse on the map to display the context menu and click on Properties

to display the Property Pages.2. Select wsiearth.tif (or the raster dataset you selected), then click Delete.

Modify the procedure that initializes the map

1. Double-click the form to display the code window.2. Modify the InitializeMap procedure by inserting the following

after all existing code:

' Add RasterLayer to the map underneath all' existing layers

Dim pRasterLayer As IRasterLayer

Set pRasterLayer = New RasterLayer

pRasterLayer.CreateFromFilePath _"E:\World\wsiearth.tif"

' Note that we are passing in an index valueMapControl1.AddLayer pRasterLayer,

_MapControl1.LayerCount

Test and save your changes1. Click the Run button in the Visual Basic toolbar.

2. Click the Stop button in the Visual Basic toolbar and save your project.

Using ESRI tools and commandsThe ArcGIS installation provides you with a set of sample commands and tools thatyou can use to customize ArcMap or in conjunction with your Map control. These tools

implement ICommand and/or ITool, providing functionality to identify and select

features and to produce attribute reports, editing commands (including StartEditing,StopEditing, Undo, Redo), and tools to add and reorganize layers. In the Bin subfolder of

your ArcGIS installation, you will see two DLLs called AfCommands andAfCommandsVB. These two DLLs contain the library of supplied sample tools that =can be used directly with the Map control. The source code for the sample tools isavailable as part of the ArcObjects Developers Kit. The following section illustrates how

to use two of these commands to provide an Identify tool and a Query tool.

Adding an Identify toolAdd the ESRI AF Commands (VB) reference to yourVB project.

1. Pull down the Project menu and select References.

2. In the list of available references, find and check ESRI AF Commands(VB).3. Ensure that the ESRI Object Library appears above ESRI AF Commands(VB).We have already added an Identify button on the toolbar.

Now we need to make three modifications. Firstly, wedefine a Private member variable to hold our Command.

The second change is in the Form_Load event where we

instantiate the private member variable, and the finalchange involves handling the clicking of the toolbar.


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1. Firstly, add a private member variable to your project by adding the following code to

the Forms code window General section. Private m_pCommand As ICommand 2. Immediately after the call to InitializeMap, insert the following

lines to create an Identify tool and pass it a reference to the Map control.

Set m_pCommand = New AfCommandsVB.Identify

' Pass the Map control as the hookm_pCommand.OnCreate MapControl1.Object

3. Modify the Toolbar1_ButtonClick procedure to associate the Map control with the

Identify command using the CurrentTool property.

Private Sub Toolbar1_ButtonClick(ByVal Button As

MSComCtlLib.Button)Set MapControl1.CurrentTool = Nothing

With MapControl1

Select Case Button.Key

Case "Zoom"

.MousePointer = esriPointerZoomInCase "Pan"

.MousePointer = esriPointerPanCase "FullExtent"


.Extent = MapControl1.FullExtentCase "SelectByPolygon"

.MousePointer = esriPointerCrosshair

Case "TrackEvent"

.MousePointer = esriPointerHotLinkCase "Identify"


Set MapControl1.CurrentTool = m_pCommand

End SelectEnd Sub

For the Map control to be able to set the CurrentTool, the target tool must support theITool interface, which the supplied Identify tool does. Internally, once the Map control

has been associated with the CurrentTool, it forwards all MouseDown events directly tothe CurrentTool first and fires the OnMouseDown event as before. If another operation

has been selected from the Toolbar, for example, the Pan, we need to reset the

CurrentTool to Nothing to indicate that no tool should be used. We do this at the

beginning of the procedure.


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Test your changes

1. Click the Run button in the Visual Basic toolbar.2. Select the Identify tool from the Toolbar. Notice that the MousePointer has changed.

Click on an individual feature or drag a rectangle and an attribute dialog box will pop up.

3. To stop running your application and return to design mode,

click the Stop button in the Visual Basic toolbar.

Adding a Query toolThe AF Commands library also comes with a very useful Query tool. This tool enables

you to query a specified layer using a spatial and/or attribute query. The results can be

Added, Kept, or Discarded to or from the Maps SelectionSet. To correctly use the Querytool (and all other tools that only implement the ICommand interface), we need to create

our tool and load it into a global variable. If we create the command using the OnCreate

method and then fire its OnClick method entirely within one procedure, it will quickly go

out of scope, and an error will be raised. Storing the command in a global variable solvesthe problem.

Alternatively, you can use a Collection to manage your tools

instead of a global variable.1. Firstly, add a private member variable to your project by

adding the following code to the Forms code windowGeneral section:Private m_pQuery as ICommand

2. Next, modify the Form_Load procedure and add the

following lines to create a new Query command and pass it a

reference to the Map control.

' Use the AfCommandsVB Query toolSet m_pQuery = New AfCommandsVB.Query

m_pQuery.OnCreate MapControl1.Object3. Modify the Toolbar1_ButtonClick procedure as shown below.

Case "Query"


' Fire the query command

m_pQuery.OnClick


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Change the Feature Selection Color

4. Finally, modify the Form_Load procedure to change the default color that is used tohighlight selected features. We shall change it so that selected features are shown in red.

Add the following code in the Form_Load procedure after all layers have been added and

their MinimumScale and MaximumScale properties have been set.

' Create a red color objectDim pColor As IColor

Set pColor = New RgbColor

pColor.RGB = 255Dim pFeatSeln As IFeatureSelection

' Iterate layers and set the color

For i = 0 To MapControl1.LayerCount - 1Set pLayer = MapControl1.Layer(i)

' Work only with feature layers

If (TypeOf pLayer Is IFeatureLayer) Then

' QI for the FeatureSelection

Set pFeatSeln = pLayerSet pFeatSeln.SelectionColor = pColor

End If

Next i

Only feature layers have a SelectionColor. To check what type of layer we have, we use the

TypeOf keyword. After we have worked out if the current map layer is an IFeatureLayer, we QI

directly to the IFeatureSelection interface and set its SelectionColor property.


1. Click the Run button in the Visual Basic toolbar.2. Select the Query tool from the Toolbar and a dialog box will

pop up. Build an attribute query by first clicking on the states

layer in the Class tab. Now click on the Attribute tab andselect STATE_NAME from the list of available Attributes. Enter

Alabama in the Attribute Value box and click Apply.


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3. Now try the Spatial Constraint. First, zoom into the Map so that the counties are

drawn. In the Query dialog, click on the counties layer in the Class tab, then click on theSpatial Constraint tab. For the Spatial Extent, click on the icon for digitizing an area and

then click on the map to draw a polygon. Select the Intersects Spatial Operator andfinally click on the Apply button.

4. To stop running your application and return to design mode, click the Stop button inthe Visual Basic toolbar

developing a geographic information system

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