Some data providers and government agencies offer digital elevation models (DEMs) as rasters. Many raster DEMs can be downloaded without charge from the Internet. For example, the USGS distributes its DEM products, which are based on USGS Digital Orthophoto Quads and Quarter Quads (DOQs, DOQQs).
When you cannot find one raster DEM that meets your requirements, you can merge several existing DEM raster files to generate a single seamless DEM to cover your project area, which is saved as a PCIDSK file (.pix). Also, if you generated your own DEMs and chose to edit them before they were geocoded, you can integrate the resulting geocoded DEMs by completing this procedure.
To import raster files and generate a DEM
- In the File box, type the path and name of a raster file or, to select a file, click Select.
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Under DEM merge set candidates, click the files you want, and then click the arrow button
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The files you selected appear in the Set of DEMs to merge box.
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If necessary, click Move Up or Move Down to organize the files.
When a raster at the bottom of the list overlaps a raster at the top of the list, the bottom raster will overwrite the top raster where the two overlap.
- In the Channel list, click the channel you want to use or, to select a channe, click Select.
- Under RasterMerging Options, in the Background value box, type the value representing the NoData pixels in the DEM.
- In the Resampling list, click the processing method you want.
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Beside Interpolate holes, do one of the following:
- To automatically interpolate data between the raster DEMs, make sure the Yes option is selected (default).
This is recommended for small gaps, but not large areas.
- If you do not want to automatically interpolate data between the raster DEMs, click No.
- To automatically interpolate data between the raster DEMs, make sure the Yes option is selected (default).
- Click OK.