Full Color Shaded Relief

Contour maps have essentially gone out of fashion, replaced by shaded relief. There are still plenty of uses for contours, but they just don’t look as cool as a well-drawn hillshade. A colored hillshade is even more exciting. Traditionally, the easiest way to do that in ArcGIS was to place a color stretched DEM over the hillshade, and then reduce the transparency of the DEM. There are two major problems with this solution. One problem is that the transparency washes out the colors in the DEM, making the image too pale and bland. (This can be alleviated by choosing extremely bright colors, or adjusting the number of standard deviations in the stretch, but never quite solved.)The other is that when a transparent DEM over a hillshade is exported as a PDF (so that it can be edited in Adobe Illustrator), the alpha values are recalculated, making the image significantly darker.

Now, through the use of some deep image processing techniques, it is possible to brighten up your DEM overlays. The trick is to use pansharpening. Pansharpening uses a high resolution greyscale image to increase the color resolution of a multi-band color image. Don’t worry if you don’t exactly understand what’s going to happen – the wonderful folks at the ArcGIS mapping blog have put together a great tutorial. Within ten minutes, you’ll be wowing yourself with unbelievable shaded relief – without the hassles of transparency.


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