GetVirtualHeightMapInBBox does not work when DEMFileRegistrationMode is Cell

[g0ro]

Trying to get heightmap in bbox, using GeoTiff dataset with Cell file format, fails when bbox is partially covered.

RasterService.GetVirtualHeightMapInBBox(...) returns a hightmap half pixel shifted. This results in incorrect height map when merging tilesHeightMap in ElevationService.GetHeightMap(....)

When DEMFileRegistrationMode is Cell, we should add (metadata.pixelSizeY / 2d) to metadata.DataEndLat, and (metadata.pixelSizeX / 2d) to metadata.DataStartLon (File: https://github.com/dem-net/DEM.Net/blob/168cd8e0e277793227f9cacd1cd26310ba495928/DEM.Net.Core/Services/Raster/RasterService.cs#L560 , Lines: 560, 566, 567, 576) Reference: https://github.com/dem-net/DEM.Net/blob/168cd8e0e277793227f9cacd1cd26310ba495928/DEM.Net.Core/IO/Raster/GeoTiff.cs#L440

[xfischer]

Hi @g0ro, thanks for reporting this. Can you submit a PR ?