MICRODEM Trend Surface
Option on

Display multiple windows with its results:
 Graph with trend surface versus DEM.
 A map window with deviations from trend surface
(difference between DEM and trend surface).
Modify this map like any other map.
 Histogram of deviations between DEM and trend surface.
 Text window with statistics. This will include the correlation coefficient r
and rē, the coefficients for the trend surface, and some
data on the goodness of fit and the variation explained
by the surface (see Davis, 1986, for an explanation of
this table).
 Map window with trend surface. Modify this
map like any other map.

This option fits a trend surface to the current DEM or database.
You should be aware of the following limitations:
The entire DEM will be fit. If you do not want to use portions
of the DEM, edit the DEM first. To speed
up the computations, the program will decimate the DEM to use 250,000
points or fewer to compute the trend surface.
All variables are in meters, with the elevation (z) and the
easting (x) and northing (y) UTM coordinates. To avoid math
overflow problems, the x and y coordinates are shifted to place
the origin at the SW corner of the data set. The shift will be
indicated in the statistics window.
 The DEM must be capable of conversion to UTM coordinates,
which will be the x and y coordinates used. The input DEMs in
mind when the option was created were USGS 1:24K and 1:250K (DTED).
 The z units should be meters to correspond with the UTM
coordinates.
Potential problems and their solutions:
 The deviations from the trend surface mirror ridges and
valleys in the valley. Consider editing the DEM to remove
the deep stream valleys.
Last revision 9/15/2016