## Multitple Grid Arithmetic (Map Algebra)

- Difference between two
grids (entire grid)
- Difference between two
grids (current map area only) When you pick the two DEM,
DEM1 - DEM2, DEM1, the first one selected will determine the area
used.
- Difference maps to all other open grids
- Add multiple grids--add
several grids together to create a new grid.
- Ratio of two grids
- Multiple Grid statistics--creates DEMs with the number of points
averaged, average (mean), standard deviation, median, floor
(lowest), ceiling (highest), and envelope thickness.
- Minimum of two grids
- Change map: make a new grid with a value of 0 where
the two grids are identical, and 1 where where is change. If
the original grids are floating point, enter a tolerance to
use for the change comparison.
- Difference elevation, slope, aspect maps: pick two DEMs, and the
difference between them for the three parameters plus the vector
normals will be computed
- Grid average/std dev (multiple
grid statistics)
- RMSE

*Last revision 2/15/2023*