Create Background Maps

Background maps can be scripted in JSL. You can write a script that creates a graph and then turns on the background map in the script.

There are two types of background maps: Images() and Boundaries(). Each of these takes a parameter, which is the name of the map to use. The name is one of the maps listed in the window.

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For Images(), the choices are Simple Earth, Detailed Earth, NASA, Street Map Service, and Web Map Service. If you use Web Map Service, then there are two additional parameters: the WMS URL and the layer supported by the WMS server.

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For Boundaries(), the choices vary since boundaries can be user-defined. A typical choice is World.

The following example uses the Simple Earth as an image and World as a boundary:

dt = Open( "$SAMPLE_DATA/Air Traffic.jmp" );

dt << Graph Builder(

Size( 1101, 603 ),

Show Control Panel( 0 ),

Variables( X( :Longitude ), Y( :Latitude ) ),

Elements( Points( X, Y, Legend( 8 ) ) ),

"Graph Builder",

{Background Map( Images( "Simple Earth" ), Boundaries( "World" ) ),

Grid Line Order( 3 ), Reference Line Order( 4 )}

)

);

图 12.31 shows an excerpt from the map:

图 12.31 JSL Scripting Example

To change the script to use a WMS server, the command would look like this:

Background Map ( Images ( "Web Map Service", "http://sedac.ciesin.columbia.edu/geoserver/wms", "gpw-v3:gpw-v3-population-density_2000" ), Boundaries ( "US States" ) )

To see which layers are available on a WMS server, install the WMS Explorer Add-In. Download the add-in from the JMP File Exchange at https://community.jmp.com/docs/DOC-6095. Note that some WMS servers are not reliable. If the server is down, or if the user does not have an Internet connection, the WMS map does not appear.

提示：

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To see the syntax for the JSL script, add a background map through the user interface. Then from the red triangle menu, select Save Script > To Script Window to see the script that is generated.

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To specify image and boundary names in the JSL script, use the names shown in the Set Background Map window. (Right-click a map and select Graph > Background Map).

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Look at sample data to find examples of background map scripts. Select Help > Sample Data Library and open Napoleons March.jmp, Pollutants Map.jmp, or San Francisco Crime.jmp. Right-click the map table script and select Edit to see the Background Map() function.