Question Re: SRTM 2 BGL program and source data

[Guest rugerdog]

Hello.I'm a new user of the SRTM 2 BGL terrain mesh program available here at AVSIM and would like to ask a question about the source data format needed to generate a source (.bat) file for the Microsoft Resample BGL compiler program.On the USGS seamless data map/download site, I can download both 30 meter and 90 meter SRTM data sets in four differenet formats: ARC, BIL, GRID, and TIFF. The SRTM 2 BGL documention only references SRTM '.HGT' file extensions as being needed to be placed in the source directory before generating a .bat file for RESAMPLE compiling. I cannot find any files with '.HGT' extensions in any of the USGS SRTM data set formats I mentioned above when downloading SRTM archive sets from the USGS. Can someone please tell me where to obtain the correct .HGT extension files needed for use by SRTM 2 BGL? Thank you very much.

[Guest sgreenwood]

Hi,The *.hgt files are available here:ftp://edcsgs9.cr.usgs.gov/pub/data/srtm/Stevewww.fs-traveler.com

[Holger 0]

Howdy:I assume that SRTM2BGL is limited to the 1x1 degree tiles available for download here: http://www.jpl.nasa.gov/srtm/pub_dist.htm Since the utility will merge the tiles for you there's no benefit I know of with using the seamless data website instead.Having said this, for the U.S. it doesn't make sense to use SRTM data at all. If you read the documentation available at the website I listed above (or do a search for SRTM in this forum) you'll quickly see that they currently are in a 'preliminary' state, with lots of voids, holes, and spikes. I'm just about to upload new SRTM-based mesh files but they are for Canada and we don't have anything better available here.Since you're already familiar with the USGS site, why not use the much more accurate NED 30-m or 10-m data instead? If you download them as BIL format, you can use them directly with resample.exe (the parameters for the .inf file will be in the .blw and .hdr files); just remember to figure out first(!) the boundaries of the area you need to select to fit with the LOD grid of your choice. Steve's website provides the necessary knowledge: http://www.fs-traveler.com/welcome.shtml ... unless you're interested in Alaska, because the NED Alaska data are in a different datum (NAD27) and need to be re-projected to WGS84 before use with FS.Cheers, Holger

[Guest rugerdog]

Thank you both Steve and Holger. I hadn't realized that the SRTM data was second rate compared to the 10 meter dems available from the USGS but you are quite right. I will go to Steve's sight and read up on 'meshing around', looks like a lot of fun really. Thanks again for all the info!