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By David Davis and Keith Mann, Esri Virtual Campus

ArcUser April-June 2001
 

Editor's Note: Data integration has long been recognized as one of the great strengths of GIS. Organizations worldwide have spent billions of dollars synthesizing and integrating spatial data for internal use. The Geography Network provides a portal that unlocks these vast resources by allowing simple, real-time, remote access to this data through the use of ArcGIS. This tutorial requires ArcInfo 8.1, ArcEditor 8.1, or ArcView 8.1 and an Internet connection.

ArcIMS, one part of ArcGIS, provides an easy way to publish maps, geographic data, and spatial applications on the Internet. An article in the October–December 2000 issue of ArcUser magazine, "Creating a GIS-Enabled Web Site Using ArcIMS," walked readers through the simple three-step process of setting up an ArcIMS site and publishing a Map Service.

ArcCatalog and ArcMap, two of the desktop applications in ArcGIS, can work with data from ArcIMS services in the same manner as data stored locally or on a local network. ArcCatalog explores and manages Internet data sources, and ArcMap displays and analyzes data. This article describes how to take advantage of connectivity with the Geography Network that is built into ArcCatalog and ArcMap. Although the Geography Network includes many types of content, this tutorial focuses on using ArcCatalog and ArcMap to access ArcIMS Map Services.

Connect to the Geography Network through ArcCatalog.

What is a Map Service?

A Map Service is a "live" map that is published over the Internet using ArcIMS. The map publisher defines the data that will be included and determines the map's geographic extent, symbology, and functionality. A Map Service can contain one or many data layers such as street networks or city points. There are two types of Map Services--Image Services and Feature Services. An Image Service is a snapshot of a map on a server that is delivered as an image and often used as a background for existing local data. A Feature Service provides more sophisticated functionality by streaming actual map features that are directly accessible by ArcMap. Characteristics such as drawing order can be changed. Data provided by a Feature Service can be used for analysis. Either type of Map Service can be accessed by ArcCatalog and ArcMap.

Typically, both Image and Feature Services consist of one layer composed of many sublayers. Sublayers can be scale-dependent (i.e., these layers are only visible at a preset scale). Layers and sublayers can be turned on and off. When using image and Feature Services, it is a good idea to investigate the sublayers and turn off ones that visually conflict with other data in the data frame. Hide a sublayer by clicking on the dash in front of the layer name in the Table of Contents.

A connection to the Geography Network server or other Internet map servers can be created in ArcCatalog to browse available data. Once an Internet server connection is added to ArcCatalog, all the Map Services available from that server are visible. This connection can be renamed with a more meaningful name, deleted, or disconnected. Simply drag and drop a Map Services icon from ArcCatalog to ArcMap to start that service in ArcMap or choose File > Add Data or click on the Add Data button to add Internet server connections. ArcMap has a built-in connection to the Geography Network. Choose File > Geography Network to access the Geography Network Explorer and browse available Map Services to locate data that can be added as layers.

Adding Map Services Using ArcCatalog

ArcCatalog must be connected to a map server before it can access Map Services. This next step will establish a connection to the United States Geological Survey (USGS) Internet server and access shaded relief raster data from the National Elevation Dataset (NED). This type of data is typically used for geographic reference or as a background for displaying other data.

  1. Start ArcCatalog. The catalog tree on the left side of the ArcCatalog window lists the connections currently available.
  2. Scroll to the bottom of the catalog tree and expand the entry for Internet Servers by clicking on the plus sign in front of it. Double-click on Add Internet Server to display the Add Internet Server dialog.
  3. In this dialog, type "edcnts12.cr.usgs.gov:8181" after http:// and make sure that "All services" is selected in the "What services do you want to connect to on this server?" section. Click OK. The USGS Internet map server will be added to the list of connections in the catalog tree.
  4. In the catalog tree, expand the new edcnts12.cr.usgs.gov_8181 map server folder by clicking on the plus sign. Click the EDCNS10_Store Map Service name, then click the Preview tab. Be patient while ArcCatalog connects to the server. After the map appears in the right panel, use the Zoom In tool to get a closer look at the data.
  5. Now connect to a single Map Service located on the Geography Network that supplies data from the United States Army Corps of Engineers showing the location of dams. In the catalog tree, double-click on Add Internet Server to bring up the Add Internet Server dialog. Type www.geographynetwork.com for the URL. Instead of adding all services, this time click "Just the following services," and click on the Get List button. Scroll down in the list of services and check the box in front of the USAC_Dams service. Click OK to dismiss the dialog.
  6. Return to the catalog tree and expand the www.geographynetwork.com folder. Preview USAC_Dams. Enlarge the Preview window if necessary. Zoom in to see the data in greater detail.
Add the USAC_Dams Map Service connnection as another layer.

Viewing Map Services in ArcMap

One of the most powerful features of ArcMap is the ability to view more than one Map Service at a time, even if these services are located on different servers in different parts of the world. Both Image Services that were previewed in ArcCatalog in the previous steps will be added to ArcMap.

  1. Start ArcMap. In the Welcome dialog, click on Create a New Map and Start Using ArcMap.
  2. Move and/or resize the ArcCatalog and ArcMap windows so both are visible.
  3. In the ArcCatalog catalog tree, select the EDCSNS10_Store Map Service in the edcnts12.cr.usgs.gov_8181 map server folder and drag it into the ArcMap display area. Once added to ArcMap, this data appears in the Table of Contents as a layer containing several sublayers.
  4. In the ArcCatalog catalog tree, select the USAC_Dams Map Service in the www.geographynetwork.com map server folder. Drag it into the ArcMap display area. Dismiss the message box concerning the difference in coordinate systems by clicking OK. For purposes of this tutorial, projection differences are not consequential. The USAC Dams Image Service contains a series of sublayers. Note that the EDCSNS10_Store Map Service layers are no longer visible.
Zoom to the Portland, Oregon area.

Inspecting the Layers

With both Image Services in ArcMap, the next step is to zoom in on the Portland, Oregon, metropolitan area. Notice that not all the sublayers in both layers are turned on. Sublayers that have grayed-out check boxes in the Table of Contents are scale-dependent. Right-click on a layer with the grayed check box to bring up the context menu and choose Properties. Choose the General tab in the Properties dialog to see the minimum and maximum scale range for that layer. Choose the Sources tab to view information on the layer's coordinate system.

  1. Choose the Zoom In button and click on the state of Oregon to zoom in on it. Continue to zoom in to the Portland area until the map scale is less than 1:2,000,000. Notice the status bar-each time the display refreshes, data is being requested from the map servers.
  2. To see the NED data beneath the flood data layer, the flood layer must be made transparent. Transparency is useful for making underlying features visible when displaying multiple layers on a map. Choose View > Toolbars > Effects to display the Effects toolbar.
  3. In the Effects toolbar, click the Layer drop-down arrow and choose USAC_Dams as the layer to adjust. Click the Adjust Transparency button and drag the slider bar to adjust the transparency to 45 percent. Now the NED shaded relief data is visible through the semitransparent flood zones data.

Adding and Modifying Data from a Feature Service

Map Services can also be added directly to ArcMap from the Geography Network without connecting to an Internet server using ArcCatalog. A Feature Service will be added directly to ArcMap in this step.

  1. Choose File > Add Data from Geography Network. The Geography Network Explorer is displayed.
  2. In the Define Search Criteria for Data Theme section, scroll to Transportation Data, located under Business Data, and select it. Click on Search. Search results are displayed on the right.
  3. Use the Geography Network Explorer to find the Esri NIMA Airport locations.
  4. Scroll to the Esri NIMA Airport Locations Feature Service and select it. Be careful to choose the Feature Service rather than the Esri NIMA Airport Locations Image Service. Click the Add to ArcMap button to add it to this map document.
  5. Again click OK to dismiss the coordinate system message. The NIMA airports will be visible. Unlike an Image Service, the symbology in the Esri_Airport_FS layer can be changed and the features used for analysis.
  6. ArcMap can be used to change the symbology used by a Feature Services layer so that it will be more legible or work with other layers from different sources that are being analyzed.
  7. In the Table of Contents, click on the airplane symbol to display the Symbol Selector.
  8. Scroll through the symbols and click on the airplane symbol. Change its color by clicking on the arrow next to the color swatch under Options. In the displayed palette, choose a shade of red to change the color of the airplane symbol and click OK.
Use the symbol selector to change the airport symbol.

This map can be saved so that when it is reopened ArcMap will automatically reconnect to the Map Services. Choose File > Save As and save the map document as portland.mxd to a local drive before closing ArcMap and ArcCatalog.

Connecting to the Geography Network using ArcMap and ArcCatalog instantly expands your GIS and makes a growing library of data and services accessible from the desktop. To learn more about the Geography Network or to search for Map Services visit www.geographynetwork.com. In addition, Esri Instructor-led and Virtual Campus courses include instruction for integrating the Geography Network with GIS software. Learn more about Esri Training and Education.

Return to Table of Contents for April–June 2001 issue


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