3D Grid Viewer Update

I've been learning OpenGL programming by writing a 3D grid viewer which uses the terrain data I'm collecting from Second Life. I put an old screen shot below. I recently changed the file format for the height data from a grayscale bitmap to a text file. Since then I've updated the viewer to use the new format and implemented a simple level of detail mechanism which operates on a sim by sim basis. The next step is frustum culling of sims.