Option is on File, Save DEM, menu when a map
has a DEM associated with it.
The Reinterpolate options will create and open a new DEM. If you want to
save that DEM, activate its window and use the Save DEM option.
This will effectively reproject the DEM or grid.
- Reinterpolate, UTM: the entire DEM will be
resampled into a UTM grid with a specified
resolution. If it is a UTM grid, it will be
resampled (either up or down in resolution). If the DEM
covers two or more UTM zones, you will be asked for the
zone's coordinates to use. You should not extend UTM
coordinates very far beyond the UTM zone boundaries.
Extending too far to the west will create negative
coordinates, and the behavior of the program in this
case might be erratic. Reinterpolation uses a bilinear interpolation.
If you are crossing the zone boundary, you should strongly consider using a
- Reinterpolate, lat/long: the entire DEM will
be resampled into a lat/long grid. If it is already
a lat/long grid, it will be resampled to the spacing you
desire (either up or down in resolution). You should pick a spacing in arc seconds
that is less than the spacing in meters; for instance, with a 150 m DEM,
pick 3 arc seconds. This will result in a larger file but retain more
of the detail. You can also decide whether to use a floating point or
an integer to save elevations; floating points uses twice the storage and
memory. Save as DTED will do
essentially the same thing, but can only store integer elevations.
Reinterpolation uses a bilinear interpolation, which MICRODEM always uses to
get an elevation not exactly on a grid node.
There is no penalty in MICRODEM for using lat/long DEMs, and all
computations use them without problems. Lat/long DEMs are much better
for seamless operations (USGS and NGA agree, and that's what is used for
NED, SRTM, and DTED).
If you are downsampling and want to consider a larger region rather than just
the four points around your desired grid postings, you can
Filter the DEM first.
Last revision 8/22/2014