Problems with Heightmaps

Hi,

I’ve downloaded a tif heightmap from http://reverb.echo.nasa.gov and converted it to RAW in Photoshop (CS2 & CS5) then imported that to Unity.
Then I’m using a TerrainImporter script to build the terrain. (unifycommunity.com)
I’m just getting some sheer edges now on my test heightmap - http://screencast.com/t/i2oZkZqZMwN8

The actual area I want to get a terrain for comes out more like a sheet of braille with the occasional pin poking through - http://screencast.com/t/qT2q3AN1

Are these issues just down to the quality of the height data or is there something more that can be done with Unity to manipulate the data?

thanks.

Heightmap resolution must be power of two plus one. The dimensions of the terrain don’t have anything to do with the resolution.