Geomorphometrics by block
From Geomorphometry analysis
option on Analyze menu. This divides the DEM into a series of rectangular blocks, and
computes statistics in each, which will be placed in a dBase table.
- Select options
- Box/region size in meters or pixels
- Min points for elevation: data voids, or edge effects have no
effect on the elevation statistics.
- Min points for SSO: SSO requires no holes in the point and its 8
nearest neighbors, so cannot be done on edge pixels.
- Select parameters.
Parameter definitions and references.
- Basic elevation: 4 moments
- Advanced elevation:
- relief, elev_relf,
- min and max elevations locations (if multiple points have
the same elevation, the result will be the first one
- characteristics of the line connecting the min and
max. This may or may not have any meaning, as they depend
on the shape of the analysis region. They make sense for
polygon shapefiles with things like a landslide or drainage
- DIST_DROP is the distance in m betweeen
the high and low points
- DIST_AZ is the compass direction
between the high and low points
- SLOPE_DROP is the slope along the
straight line distance
- Slope: max slope, and 4 moments
S1S2, S2S3, FABRIC_DIR: S1S2, S2S2, fabric direction, shape, strength,
roughness, and average aspect. Requires a box size.
These will be blank if there are not enough valid points to compute
the statistics. You can reduce the number of points required
using the ASPECT_PTS or SSO_PTS fields.
- ASPECT_AVG: Vector average of the aspect (downhill
- ASPECT_STR: strength of the average aspect. It will be
0 if there is a completely random orientation, and 1 if they all
point in the same direction.
- Profile curvature: 4 moments
- Plan curvature: 4 moments
- Openness: 4 moments each of upward and downward openness.
Requires a box size.
- Less useful
- Gamma: nugget covariance from variogram
- Fractal will slow things down, and the results may not be
worth the effort.
- Wavelength/height is currently disabled
- You can only turn groups off or on.
- The program will create a database with desired parameters.
You can alternatively
create grids, for these and some other
last revised 8/29/2017