Full text: Proceedings, XXth congress (Part 8)

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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 
2.3 Application Development 
In this study a GIS application was developed and a web site 
was configured to serve the earthquake information on the 
Internet. MapObjects activex component was added to a form in 
Visual Basic project file and used to develop the application 
(Figure 5). WebLink.ocx is also an activex control. This 
control is installed automatically with MOIMS. Its role is to 
listen on an assigned port for requests from a client and 
communicate with the esrimap.dll. Esrimap.dll is a dynamic 
link library component that extends web server software. It can 
manage requests and responses from map server and administer 
map services (ESRI, 1998). Following functions can be 
implemented in programs built with Map Objects control: 
e Display a map with multiple map layers, such as 
roads, streams and boundaries. 
e Pan and zoom throughout a map. 
e Draw graphic features such as points, lines, ellipses, 
rectangles and polygons. 
e. Draw descriptive text. 
e Identify features on a map by pointing at them. 
e Select features along lines and inside boxes, areas, 
polygons, and circles. 
e Select features within a specified distance of other 
features and more...(ESRI, 1999). 
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Figure 5: Visual Basic project with components 
The map control is the main object of the MapObjects. The map 
control is a container for the maps. Maps are displayed on this 
container. MapObjects ActiveX control has lots of properties, 
events and controls. Main properties are CoordinateSystem, 
Extent, FullExtent, MousePointer and Visible. Main methods 
are DrawShape, ExportMap, Pan, Refresh and TrackRectangle. 
Main events are  AfterLayerDraw, | BeforeLayerDraw, 
MouseDown and MouseMove. Before adding any vector layer 
a data connection must be established. A data connection 
represents a connection to a source of geographic data. In this 
study a folder containing shapefiles is the data source. A 
connection can return a GeoDataSets collection. Each member 
of the collection, referred to as GeoDataset, represents a 
discrete set of geographic data that can be retrieved from the 
data source. Geographic data in a GeoDataset is used by 
assigning it to the GeoDataset property of a new | MapLayer 
object. The Connect method of the DataConnection object will 
attempt to connect to the data source specified in the Database 
property. Following is the codes for adding layers to the 
add shapefiles 
Dim dc As New DataConnection 
Dim Lyr As MapObjects2. MapLayer 
dc.Database — ImsDataPath 
If Not dc.Connect Then 
MsgBox "ims data set not found" 
End If 
Set Lyr = New MapLayer 
Set Lyr.GeoDataset = de. FindGeoDataset("Seismic") 
Lyr.Symbol.SymbolType = moPointSymbol 
Lyr.Symbol.Style = moSquare Marker 
Lyr.SymbolColor = moRed 
Lyr.Symbol.Size = 9 
Lyr. Visible = False 
Map. Layers. Add Lyr 
2.4 Serving on the Internet 
GIS application runs together with MapObjects Internet Map 
Server components. MapObjects Internet Map Server acts as a 
gateway between Web Server and the mapping application. The 
request made by the client is passed to the web server first. The 
server recognizes that this request is about creating a map, so it 
directs it to the map server. The map server executes the 
application according to the type of mapping demand (this 
demand can be a display operation like a zoom-in function or a 
query about a feature) and sends the result (a picture of the map 
in JPEG format) to the web server. The web server brings the 
HTML page created to the client. MapObjects IMS has three 
different components that runs one after the other. IMS Catalog, 
IMS Launch, and IMS Admin are connected to each other. IMS 
Admin communicates with IMS Catalog to manage the state, 
running or not, of a map service. IMS Catalog communicates 
with IMS Launch. When starting a map service, IMS Catalog 
sends the path and file name of the map service to be started 
and the number of instances to start. IMS Launch responds by 
starting the map service. 
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Figure 6: Server side of the application 
When a client sends a URL request to the server that hosts 
esrimap.dll, it determines which map service to communicate to 
respond the request. The URL address : http://ServerName/ 
scripts/esrimap.dll?Name-MapServiceName&Cmd-Map. Each 
argument and value pair is referred to a query parameter. The 

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