I Used this method to quickly create a 3d model based on a terrain I built in SL (I wanted it for experimenting in VastPark and Unity)

1. Export a RAW terrain file from SecondLife. You need to be estate owner or ask the estate owner to do this.. (Region/estate menu –> terrain –> Download RAW terrain)
2. Open the RAW file in PhotoShop using the following import settings: 256×256, no header, 13 interleaved channels.
3. turn off all but red channel (should look like a greyscale version of the sim from the air)
4. select all and cut and past into a new file so you only have this grayscale channel as a single layer
5. save out as a Targa file, 24 bit
6. follow the instructions on the following page, starting at the heading–> “Create grid and add the image as texture”: http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Making_Landscapes_with_heightmaps BUT I recommend ‘unwrapping’ the mesh when it is a flat grid for UV texturing later (so unwrap and create UV image before you start to click the noise button)
7. texture by painting the UV or using the technique outlined here: http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Landscape_Modeling_II:_Texture_Stenciling (which will allow you to replicate SL style land texturing by painting areas where different textures will blend across the terrain surface