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Categorized Aspect Map

by Technical Evangelist on ‎08-30-2018 12:04 PM - edited on ‎02-24-2020 03:32 AM by Community Manager (796 Views)

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Derive a terrain aspect map from input DEM data. The user has control over whether the output are floating point values representing true compass bearing, or if the data are categorized into a limited number of classes representing North-facing slopes, North East-facing slopes, etc.


Left View shows the original DEM styled using the Relief Image Chain, Right View is the Categorized Aspect Map


This Spatial Model determines the direction a surface is facing by calculating the elevation of each pixel relative to its neighbors. It offers two output options: Categorized (cardinal directions) or not (degrees).


When Categorize Output is true, the surface orientation of each pixel is expressed as one of nine classes representing the cardinal compass points (64=N, 128=NE, 1=E, 2=SE, 4=S, 8=SW, 16=W, 32=NW, 255=flat).


When Categorize Output is false, the surface orientation of each pixel is expressed in degrees clockwise from north (0° to 359.999999°; flat areas are coded as 361).




Input parameters: 






Default Value or Behavior if not Required

Aspect Filename Out IMAGINE.File

The name of the output raster dataset. The output dataset will contain a single band. If Categorize Output is false, the pixel type of the output raster dataset will be single-precision floating point; if Categorize Output is true, it will be unsigned 8-bit.


A text metadata file (<Aspect Filename Out>.metadata.txt) will be created side-by-side with the raster output. This file contains the name of the input file. If the input raster is a DTED, the metadata output also contains the following items:


  • Series Designator
  • Absolute Horizontal Accuracy (meters)
  • Absolute Vertical Accuracy (meters)
  • Point to Point Horizontal Accuracy (meters)
  • Point to Point Vertical Accuracy (meters)
  • Security Classification
  • Security Handling Description
  • Data Edition Number
  • Match Merge Version
  • Maintenance Date
  • Match Merge Date
  • Vertical Datum
  • Horizontal Datum
Categorize Output IMAGINE.Bool

If set to true, the terrain aspect information is grouped into nine distinct classes representing cardinal directions, including one for flat or horizontal surfaces. If false, the output raster will consist of values representing the compass bearing of the slope at each pixel location (with flat areas coded to 361).


Categorized classes:


Terrain Filename In IMAGINE.File The name of the input raster dataset. The last band that has a vertical coordinate system (Elevation Info) present will be processed, or, if no bands have a vertical coordinate system, the last band in the raster will be processed.  (tick)