Our data comes from real world satellite survey heightmaps, so for our projects all height need to be accurate in z to around 0.5m, so no Mudbox or Zbrush is not the solution. The reason we need real elevation data is that we are making railways, road projects and city planning. Greyscale maps dont contain real elevation data, they only contain 65,536 shades of grey. The problem is that there is no correlation between the shades of grey and their real world heights. If the total height between white and black are known then its possible that it could be scaled somehow. But UE4 doesnt even seem to have a min and max value that can be entered, so im guessing that scaling is the only way. Weirdly enough UE4 wont even accept unity raw 16bit images, so thats a good example of why RAW is an overly complex format.