You have set Global Mapper to interpolate elevation values smoothly between elevation centres, reporting interpolated Z values in the status bar. It does this using bilinear interpolation by default for elevation values, but there are several other options, including no interpolation (nearest neighbour). It's arguable that this is appropriate for rasters modelled as sample points (grid-centred) though not for grids modelled as squares or pixels (cell-centred). There's room for disagreement on that though, and there is no single right answer for all data on either paradigm or for all purposes. Manifold does interpolate automatically for some purposes (including Surface Transform and reprojection) but not for Z readout in the status bar. (This is broadly in line with Manifold treating all surfaces as cell-centred, not grid-centred--but again there's room for disagreement.) Note that Manifold is not reporting averages--on the contrary it is reporting actual data values, without blending or smoothing. Why is it important to you that you get interpolated elevation values reported in the status bar, for this data?
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