Let me give you a brief general introduction first:

  • For this tutorial I assume you have free tools and data in mind, and that you use FS9. If you're willing to spend money, you can reduce your efforts a lot, and there's a plethora of commercial stuff for GIS data conversion in high quality out there. As a small overview there's quite a list hereI was extremely impressed by Global Mapper, which seems to fulfill every possible wish regarding the easy retrieval and conversion of elevation data.
    Anyways, the free resources we're using here are somewhat limited, of course. 
  • Be prepared to invest a lot of time and probably get frustrated or even irritated when you  – for which reason ever – leave the easy path pointed out here on the basis of free tools only. GIS data are available in hundreds of formats which seem to be very hard to convert: Even professional programs only cover a very limited range. Data conversion is one of the most difficult tasks you'll have to manage.
  • Freely available Elevation Data (especially older SRTM1 data) will most likely have many void spots, and therefore have to be processed / interpolated. Otherwise you’ll see deep holes in your FS environment later! (see: Advancing Your Scenery)
  • You'll find a lot of information in the SBuilder Help documents and in the SBuilder Forum. Don't forget to "study around" and get some basic understanding of it... you might even see your first own results with some pride, once you realized how difficult the "thing" is!
  • There are other scenery elements which affect mesh: Flatten polygons override it with their particular height (e.g. airfields) as well as  water polygons do, and VTP lines also influence the terrain underneath the line in a number of ways. If the result you get in FS doesn't come up with your expectations in detail, the reason doesn't necesssaily have to be the mesh.
  • If you don’t have a very particular area and want to avoid re-inventing the wheel, you can go there and download nice, free meshes for big parts of the world – most of them in ready-made BGL format. The CFS2 meshes offered there work for FS9 as well.

As an overview, here are the few simple steps described in the following are:

  1. Start this tutorial with a sample scenery
  2. Find and download the required Elevation Data
  3. Convert the data to SBuilder BMP format 
  4. Calibrate the Heightmap, select your mesh area and compile (BGL)
  5. Put the files into a scenery folder and activate the addon scenery in FS
  6. Enjoy :-)