editing finished SRTM data

[Guest davidglaister]

Hi sometime ago I used SRTM data with slarti to remesh a small area. Now I have added a few scenery objects in the same area I have found I have to make a small adjustment to the mesh.I would like to use the finished SRTM data, but I cannot download it in hgt format.Is it possible to download the SRTM data, make a few small height adjustments, and then save it in hgt format.Thanks, David

[Guest jimkeir]

Hi,You can edit the mesh using the method I described in the Slarti manual. Cinepaint is (was?) extremely clunky but did get the job done.The original format of the data shouldn't matter a huge amount. It depends on where you get it from. It'll either be in one-degree blocks of raw data or in a GeoTIFF. If it's raw, use the RAW Cinepaint plugin I provided; if it's GeoTIFF it should load immediately.Does anyone else know of any programs that allow 16-bit image painting that are better than Cinepaint?HTHJim

[Guest Horst]

Hello,Sorry not knowing a freeware tool.But in addition to your tutorial, when allowed, since Photoshop 8.0 it is better.Maybe some user getting ideas, and maybe having 8.0 or higher, reading this also:http://www.shadedrelief.com/dem/dem.htmlfor areas, we can not have good free data.RegardsHorst

[Guest davidglaister]

Thanks for the advice.I have been having a nightmare with this for two weeks, trying about 20 different progs to edit/convert dems. It was like banging my head against a brick wall. If a utility could edit a type of dem, another utility could not read it.I tried Microdem, Blackart, 3Dem, LandSerf, Global Mapper, GridConvert, GeoTiff4 etc. But none of the progs formats appeared to be suitable to the other, or could not edit/read a dem format.I was hoping to use the a GeoTiff in Microdem, use the "Edit Dem Grid" function to sort out the small areas that needed adjusting, then save that as a "Microdem Dem", and use MDem2Dem to convert it into a format that BlackArt could read, but this wouldn't work either ( not sure if Microdem has changed its format since the utility was written ).I have a useable result by using BlackArt to edit my original hgt file and using windows magnifier utility to zoom in on the area.The most stable prog was 3Dem, most other progs could read its formats, but you cannot edit single elevations.Another odd thing was that the "USGS ASCII" export format from Microdem could not be read by any other prog, maybe it was something I was doing wrong?David

[Holger 0]

Hi David,welcome to the world of GIS in general! I have been in this "business" (as a researcher) for almost 20 years now and with almost all projects a huge amount of time is spent (i.e., wasted) getting source data of differing format and resolution into a clean database to work with. And it's just the same for FS design work.I've done some hand editing of raster elevation data for FS twice, both times with the editing function of MicroDEM. As you probably know by now it's a very clunky tool and if I have to do this again I definitely will look into other options first (Photoshop 8 is a bit expensive but seems to be nice for this task).In my case I didn't use SRTM data as a source but the way I'd approach this is to do the base interpolation first (in Blackart or Slartibartfast), then import the resulting file into MicroDEM, do the hand editing where needed, then export the final version as 16-bit BSQ, which can be processed directly by resample.exe.The other option might be to do the editing first and then do the mesh interpolation and generation in Slartibartfast. I recently tested Slarti's interpolation algorithm with SRTM data and it is almost as good as Blackart and beats MicroDEM, 3DEM, SRTM2BGL, and other options hands-down (I'm not talking accuracy, which is a bit of a moot point for interpolation, but rather believability in the sim of the interpolated sections).Please let us know what procedure you end up using. Good luck!Cheers, Holger