a) Using standard library - based on geotiff intensity from LIDAR converted by using GDAL, or standard GeoTiff with noisy intensity values. Errors are coming from mismatch heightmap between neighboring tiles.
b) Triangle.NET library. Static mesh terrain from x y z csv dataset. accurate representation and height, however static mesh is not easy to put texture on it. Even, after static mesh conversion into normal Unity Landscape, the texture stretch and looks awful
However, Unity Triangle.NET triangulated static mesh let you perform complex iterations.