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I have converted a TIN to a raster. I found that the top of a bund wall shifts laterally in position between the TIN and the raster into which it has been converted using the TIN to raster tool in ArcGIS.

What is the reason for this? Does this type of thing always happen? Will it be sensible to do volume calcs using the raster with this type of problem or should I stay with the TIN?

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It is a fundamental issue. Each cell in a raster DEM represents a point height interpolated into a square.Between two raster cells there is thus a "vertical drop".

A TIN however takes those height points and draws a slope between them. There is no "true" value for any location between the points, it is just two different ways of interpolating the known values to unknown locations. The precise location of peaks, ridges and troughs is thus subject to a margin of error within which different interpolations will give different results. Thus there is no "true" volume under such a surface. So if possible calculate both ways and use the difference as an indicator of the error margin to the result.

  • I like this perceptive idea of calculating both values from both surfaces, thanks. – ndthl Dec 4 '13 at 11:01

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