Topo Fabric Overlay

 Access from Calculate,  Topographic Grain menu when active map window has associated DEM

Modify topographic grain overlay display and wavelength/height:
Plot: erases any overlays, and draws  New base map: save current map so you can have several different overlays (for instance different region sizes, each with a different color) OK--done Cancel Help

 

 

Organization Tab

  • Point separation: the distance between points at which the grain will be calculated.
  • Region size: the size of the blocks over which the fabric will be calculated. Do not make this region too small or you will not get reasonable statistics.
  • Sampling increment: speeds up computation by not using every point in the sampling block.
  • Amplitude distance
  • Min points for SSO: requires this many points for statistical validity.
  • Organization cutoff: less organized points will not be plotted.  The larger the value selected, the fewer points will be plotted.
  • Flatness cutoff: flatter points will not be plotted.  The larger the value selected, the more points will be plotted, but they might be subject to random noise. The appropriate value depends in part of the scale of the DEM and the relief in the region.
  • Length multiple: scaling factor for length of fabric vectors when they are plotted. This is an integer by which the topographic strength will be multiplied, and the result will be the length in pixels of the vectors.
  • Fabric: color and line width
  • Force redraw: using new cutoffs, length multiple, or fabric line style.
  • Plot fabric: compute and plot relief slope inflection
Wavelength tab

 

Inflection create map with locations on the map, and inflection distance, and the height.

 

Best results on Contour map or grayscale reflectance map.

The lines point in the dominant direction of the ridges/valleys.  The length of the lines reflects how strongly the orientations favor the dominant direction.

Regions with no vectors do not meet the flatness cutoff--they are too flat.

 

Aspect rose diagram: directions of organization vector, created from database (Stats button on table display window).  The vectors have a 360 degree distribution because they use the downhill direction, and
  • one side of the ridges can be steeper than the other, leading to fewer points on that side
  •  region might not include both sides of the ridge.

Last revision 11/28/2014