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Posted by crb on October 17, 2006, 12:56 am
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greetings.
i could use some help on trying to figure out how to complete a task w/
ArcGIS 9.0.
i have a map that represents the calculated differences bet. two raster
datasets (DEM data). the map represents the difference in elevation
due to erosion or deposition along a river valley. i used the ArcGIS
raster calculator to calculate the DEM diffs and classified the results
in the symbology window into 16 different categories.
for example, my classifications for the 1m DEM data are as follows:
-70 -> -21
-20.9 -> -18
-17.9 -> -15
. . .
-3 -> 0
0 -> 3
3.1 -> 6
. . .
where negative numbers represent erosion in meters and positive numbers
represent deposition.
now that i have this classified map, i need to calculate the actual
volume of debris that has been eroded or deposited for each
classification. so for each class i would multiply the total area in
square meters by the average erosion/deposition for that class. for
example, to calculate the average volume of debris deposition in the 0
-> 3m category, i need to find the total area represented by the 0 -> 3
m class and multiply it by 1.5 (i.e. the midpoint of 0 -> 3).
so my question is, how do i find the area of a given symbolized class,
in order to perform the volume calculation?
it's not readily apparent to me how to do this from the symbology tab
or the raster calculator. i've browsed the help pages and done other
web searches but nothing exactly fits the bill.
any thoughts?
thanks,
~~crb
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