A Better Hillshade

Sometimes ArcGIS creates a lousy looking hillshade. Too much contrast. Too bumpy in flat areas. Easy to fix if you add a Z-factor. Also, check out this Hillshade Tools script by Aileen Buckley.

1.) Create a Hillshade raster from the DEM (Spatial Analyst > Surface > Hillshade tool).

2.) Adjust the Z-factor using this table of values:

Approx Latitude           Z-factor (for DEMs in meters)
0                                     0.00000898
10                                   0.00000912
20                                   0.00000956
30                                   0.00001036
40                                   0.00001171
50                                   0.00001395
60                                   0.00001792
70                                   0.00002619
80                                   0.00005156

* If your DEM is in Feet units, see this LINK.

For example, say your DEM covers an area located on the Idaho-Utah border. This is about 40 degrees N, so choose the Z-factor of 0.00001171.

3.) Other improvements you might make to the display:
– Set the Hillshade Display to BILINEAR (Properties > Display > Resample during display…).
– Adjust Transparency to about 50%.
– Move Hillshade above DEM layer.
– Change DEM color ramp to Elevation #1 (Properties > Symbology > Right-click color ramp bar > uncheck Graphic view > names of color ramps appear).
– Change the Stretch Type for the DEM to Standard Deviation (Properties > Symbology).

4.) Alternatively, install Hillshade Tools and choose how you prefer your hillshade to be illuminated: Swiss-style or MDOW-style. See blog entries at THIS LINK, too.

Refs
Cfry at ESRI, 2007, Setting the Z Factor parameter correctly:

http://blogs.esri.com/esri/arcgis/2007/06/12/setting-the-z-factor-parameter-correctly/

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