smoothing vector lines

[scott967 62]

I've been using the SRTM water body shapefiles for coastlines. It appears these were developed from the 30m data. It looks like there is good accuracy, the problem is that when you look at it in the sim it looks bad -- all the coastline is 90 degree turns.My question is, is there some tool that I could use to process the vector data to get rid of this artificialness? What I was thinking was some way to smooth the data, and then maybe add some random noise.scott s..

[LuisFelizTirado 33]

Hello Scott,I agree with you - the accuracy is reasonable, but it does lack in detail (because of the military requirements, probably. Not that the military limits public access to this, but that they do not want greater accuracy for their own use!)You can try appending the shapefile in SBuilder and then use the Check Poly function. I use a value of about 200 for large coasts and about 100-150 for smaller lakes and this gives good results.In this view, you can see the smoothed polygon and the original blocky line under it:http://forums.avsim.net/user_files/147802.jpgIt does not compare, however, to drawing the coast using a topographic map - much better results. Best regards.Luis

[scott967 62]

Thanks -- will give that a try.scott s..

[Holger 0]

Hi there,that's an interesting approach, Luis, and looks like it does generate good output.I haven't worked with those SWBD directly but would probably opt for Jim Keir's "Slartibartfast", as it has two different parameters that control smoothing, will compute fixed lake elevations based on the elevation data, and also compiles the mesh and a basic elevation-dependent land class file at the same time. What's particularly nice about the mesh generation is that Slarti uses the best interpolation algorithm I've tested (and I've tested a lot!) for the gaps in the SRTM data, with the possible exception of John Child's "Blackart" (which is a separate utility and has much longer computing times).Cheers, Holger

[LuisFelizTirado 33]

I agree with you, Holger. For the money (no, wait, it's free!), Slarti is the best way to make this kind of scenery. And many thanks to Jim for such an amazing program. The automatic rivers feature is my favorite - all I can say is, "wow!"On the other hand, the Sbuilder approach is infantile in its simplicity. Append the blg, select the polygon, set the value for CheckPoly and click on Auto Check. That is it.Results are pretty good, but, as I mentioned, a map is much better since the SRTM data does not include much detail. Particularly drainage that really gives terrain a realistic appearance.Here is an SRTM water mask as seen in TMFViewer:http://forums.avsim.net/user_files/147983.jpgThis is the same place, but using a detailed map:http://forums.avsim.net/user_files/148001.jpgAdmittedly, there is a lot more going on here, but then, that is the advantage of a map.And here is how it looks in the game.http://forums.avsim.net/user_files/148002.jpgNotice particularly the drainage and how all the tributaries and branches are drawn. This is particularly impressive when flying and, as far as I am concerned, is the most missed element in the default terrain.In sum, and as I surmised when the SRTM water was first released, the principal advantage to this source of data is that is aligns with the DEM. Otherwise, though, a good topographic map will give much better results.Best regards.Luis