Displaying iMaps Tool

You can easily create map visualizations using the Tool Palette in the IDL Visualize perspective or from the command line with the IMAP command. Either way, the visualization displays in the IDL iMap tool, which allows you to visualize, modify, and manipulate maps in an interactive environment.

The interactive iMap tool gives you great flexibility in manipulating and visualizing map data. The iMap tool also allows you to manipulate and edit individual components of a map display, such as rivers, lakes, or national or state boundaries.

Displaying Maps using the Tool Palette

This example displays a map image warped to a map projection.

  1. Make sure you are viewing the IDL Visualize Perspective. (Click the Visualize button (viz_button.gif) in the upper right of the Workbench.)
  2. At the IDL command line, type the following (or click on the code below):

    3. READ_JPEG, FILEPATH('Clouds.jpg', $
    SUBDIR=['examples','data']), clouds

  3. The CLOUDS variable appears in the Variables View.
    map_mercator.gif
  4. Drag the CLOUDS variable to the Map Visualization tool.The iMap window appears, with the IDL Map Register Image dialog on top.

 

 

 

Note
Registration lets the iMap tool properly display image data in the map projection you select.

  1. The default selection is Degree. Accept that selection by clicking Next.
  2. IDL Map Register Image Step 2 dialog appears. Accept the default values by clicking Finish.

    3. The map image displays with the Mercator projection.

Displaying Maps using IMAP

We'll start by simply displaying a projection and then adding a map to the display:

  1. To open an iMap window, type IMAP at the IDL command line. An empty iMap window appears.
  2. To open and view a projection, select Operations →  Map Projection from the iMap menu. This command opens the Map Projection dialog, shown here:
    map_projection_dialog.gif
  3. Choose a projection from the Projection pull-down list. A preview displays in the dialog. (The example here uses the Mercator projection.) Click OK.
  4. The results in the iMap window show just the projection, without other mapping elements.
  5. To show the continents against the projection, select Insert → Map → Continents. The continent outlines now display in the iMap window against the Mercator projection:
    imap_mercator.gif

 

 

 

 

 

The iMap tool is a good way to familiarize yourself with projections. For example, with a basic global map such as this, you can easily change the projection by clicking Edit Projection in the Map tab on the right side of the iMap window. In the Map Projection window, select another projection and it displays in the preview window. This example shows the Mollweide projection.

imap_mollweide.gif

To draw a map that looks more like a globe, use the Orthographic projection. Choose other projections to understand the differences in how they display maps.

See Map Projections for more on the map projections that IDL supports.