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I am trying to calculate the volume of several DEMs in order to obtain elevation and volume changes. I have pixels of 1x1 each one associated to an elevation. I used several methods but non of them gave me the same results.

First method: I multiply the total sum of the dem elevation, obtained in the statistics of it, by the area of one pixel. I subtract two consecutive DEMs in order to obtain the total volume change.

Second method: I use the Volume and Area Calculator of the 3D Analysis Tool. I subtract two consecutive DEMs in order to obtain the total volume change.

Third method: I use the Cut/Fill tool in order to obtain the gain/losses of volume between to consecutive DEMs. Total gain minus total losses will give me the total change.

Forth method. I subtract to consecutive DEMs in the raster calculator and I obtained the volume of this new raster using the pixel method (first one) and using the Volume Calculator (second one).

None of these methods gave me the same results.

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    First off - are your DEMs concurrent (e.g. are the pixels of all DEMs of the same size and in the EXACT same position)? – Radar May 6 '13 at 17:56
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    By how much do the various answers differ, compared to the average answer? – whuber May 6 '13 at 17:58
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    I checked the DEM and all the pixels have the same resolution and all the DEMS have the same extend (same top, bottom, right and left).... I do not know what is wrong! – Shirin May 7 '13 at 9:47
  • The results are very similar between using cut/fill and the fouth method using the pixels sum to obtain the volume. – Shirin May 7 '13 at 9:48
  • However, using the first one are very different and using the second one even more. I also need to calculate from each DEM the volume above and below a reference plane. But I do not know if I can trust in the Volume and Area calculator form the 3D Analysis Tool. I have spent the last two days on this! – Shirin May 7 '13 at 9:54
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The most basic method to calculate the change in DEM volume for each pixel is

v = (DEM2 - DEM1) * A, where A is the pixel area. The total volume change is the sum of all resulting pixel values.

It seems to me that method 2 does exact the same thing. If it didn't work with any of the three methods, then you should consider changing your tool for this task. Try simply the raster calculator (the name varies from GIS to GIS) as this functionality is available in all GIS' and image processing software in some form.

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you might consider using the GCD tool by Joe Wheaton. On his website (gcd.joewheaton.org) you will find many information and also the scientific reference about how he takes into account errors and error propagation. I am using the tool myself and it's pretty solid, I really like it.

Hope that helps

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