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11.G.v. Importing into Clark University's Idrisi

Users of Idrisi may import the DEM and source/lineage files (GUNZIP decompressed) using the following procedure. Importing the northwestern tile of GLOBE (file a10g) into Idrisi is presented as an example.

  • Copy the a10g.doc (IDRISI ASCII DOC file described in Section 11.F.ii), globd256.smp (IDRISI binary color palette file described in Section 11.F.ii), and a10g (elevation data) files into same disk location. Rename the file a10g to a10g.img.
  • Start Idrisi for Windows. Click on Display and enter a10g. Under Palette Options click on User Defined and enter globd256 (or double click and select this palette). Confirm that the Autoscale image for display option has been activated (this should happen by default for integer data). Click OK to get the display.
  • To standardize the display colors, the number 8752 must be substituted for the actual maximum elevation for a tile in its .doc file. This may be done by hand editing the a10g.doc file, or by running Document. On the top line of Idrisi for Windows, click on File, then on Document. Enter a10g and click OK. Replace the actual maximum value for the file with 8752. Click OK.
  • Display the data as shown above. This will autoscale the display colors uniformly for all data sets. The zero and negative values are all displayed as black, but if queried, the correct value is displayed.
  • To replace 8752 with the actual maximum value for the file, run Document on the a10g file. Next to the window for maximum value click on the button to Calculate. This puts the actual maximum and minimum back in their appropriate boxes.

The files can also be imported by running Document, specifying the data type (integer for DEMs, byte for source/lineage files), grid cell size of 0.00833333, and coordinate range for the specific GLOBE tile. You can have Idrisi automatically find the maximum and minimum values for the DEMs, or you can enter the values from Table 3 (Section 11.C) to avoid waiting for Idrisi to check each large file for maximum and minimum value.

Idrisi for DOS ASCII color palette files are also available: globd16.pal is for the COLOR module; globd256.pal is for the COLOR85 module. See documentation for Idrisi versions 3.x or 4.x regarding the use of user-defined palettes in these modules.


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