That syntax is fine, although Geom([Geom (I)]) is equivalent to just [Geom (I)]. You can use any of these. If geoms are areas then all the results are the same. Height([Surface], [Geom (I)]) HeightAvg([Surface], [Geom (I)]) Height([Surface], [ID]) HeightAvg([Surface], [ID]) In principle, Manifold uses the whole pixel, just as if it were itself a square area. If any part of a pixel falls within an area, then in principle its height is counted. However, there are coding anomalies which can become significant when area size approaches pixel size. (I reported bugs in 2009/2010 and had confirmation from Tech explaining the cause. I can ask their permission to post the response in case of interest.) Depending on your data, this could be enough to give differences compared to results in Arc. They would normally be minor, unless the size of the measurement areas (or detail in parts of the areas) is comparable to the size of surface pixels. Do you want to have a second set of eyes look over your data, to see if that might apply?
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