Mesh for small zones

I would like to modify the hilly reliefs of a dwarfish zone (16 squared Kms) so that the scenery that I have created results positioned to the correct altitude. I have not given DEM of the zone but I possess one detailed altimetric map in staircase of grey. I have tried with Gmax and the command "displace" but the problem is that FS sees the hills as an object and therefore you cannot be landed us above. I have tried with the "Re-mesh" of ground2k but the detail from me in demand it is not possible to have him. Is there some program freeware or also payware that gives the possibility to recreate the meshes in way detailed for a small zone departing from an image in staircase of grey? Thanks Antonio LB-TMY I-TOMY