# How to calculate the volume of several DEMs to obtain elevation and volume changes?

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 and I am starting to despair.

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).

Non of these methods gave me the same results and I am really worry about it. I will really appreciate if someone knows how to obtain the volume of a DEM.

Thanks!

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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
By how much do the various answers differ, compared to the average answer? – whuber May 6 '13 at 17:58
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