Volume Calculation of Area for Reservoir Analysis using Grass

[Simon Cox]

I think you could replace steps 5-9 with a simple awk program.
But anyway, ain't grass+unix tools wonderful!

Simon Cox

> Yes, GRAASS can be used to do volumetric calculations.  There is no
> straightforward program, but the following outline will start you
> in the right direction:
>
> 1) Use the screen-oriented digitizing capability to outline the anticipated
> extent of the area for which a volume will be calculated.
>
> 2) Use the masking program to mask into this area
>
> 3) Subtract the DEM values from the fill height value using r.mapcalc
>
> 4) Run r.stats on the results
>      You now have something like:
>        -1  1357
>        1   3456
>        2   1234
>        ...
>        (The first value is the delta h (height), the second the area)
>
> 5) Filter out negative values (areas where the DEM height is greater than
>    the fill height). (Use sed(1))
>      You now have something like:
>        1   3456
>        2   1234
>        ...
>
> 6) Turn the output into a bc(1) input script where the height values are
>    multiplied by their corresponding area values.
>      You now have something like:
>        1 * 3456
>        2 * 1234
>        ...
>
> 7) Send the result through bc(1)
>      You now have something like:
>        3456
>        2468
>        ...
>
> 8) Sum these values; add the appropriate dc(1) commands:
>      You now have something like:
>        3456
>        2468 +
>        ...
>        p
>
> 9) Send through dc(1) for your final volume
>
----
__________________________________________________________________
				Dr Simon Cox
         __  L				
      ,~'  L_|\            	Department of Earth Sciences       
   ,-'         \         	Monash University    
   (            \		Clayton  Vic  3168  Australia
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              u   		Fax   +61 3 565 5062
				simon at cerberus.earth.monash.edu.au
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