26 replies to this topic

[Martin Gamache]

Anyone had any success loading SRTM 30 data in .DEM format into Arcmap.
The data was downloaded from:ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM30/

I followed the instruction provided here:
http://support.esri....l...how&d=22749

but was unsuccessful and got errors when trying to convert the .bil file to a grid.

I'm now on a linux machine (not by choice) and do not have access to winzip so I'm not sure if the decompression software I have access to is corrupting the TAR file or if the problem is somewhere else.

mg

[CHART]

Martin, not sure if this ArcGis extension could help. I have used the MapInfo one and it does a nice job of translating various grid format.

http://www.geomatics...s/GTPArcGIS.htm

[Brian Moran]

Hey Martin-

That data can be directly read and exported as a grid by ArcMap in 9.2. I assume you're on 9.1 or earlier? If so, my only suggestion would be to make sure your hdr and prj files are in the same place as your dem, and open them in a text editor to check for corruption. Also, you could try using the "copy raster" tool in place of the "export > raster to different format" process the instructions suggest... and use no file extension for your output to specify a grid. good luck...

[Martin Gamache]

Thanks Brian,

[Cartisan Maps]

Martin, have you found a solution?

When you originally posted, I thought it a little odd as I've worked with SRTM data before and it was easy to import. However, this time I received the same errors. Didn't have ny good input for the thread, but I was still interested in the outcome. But much to my surprise, it turns out I need to use SRTM data for a project, and many of the tiles I've downloaded are giving me the same error.

I've used the same site as you, and then uncompressed and imported the files in the exact same manner. Out of all 27 global tiles, 11 failed.

Headers and projection files are appear to be normal.

Export to Different Raster Format fails.

Copy Raster fails.

I was looking for another efficient download site for SRTM v2 data, and haven't had any luck. I did find a source for SRTM v3, and am currently downloading it (ftp://srtm.cgiar.org/srtm_v3/SRTM_Data_GeoTiff/).

Brody.

[John Lovaas]

I downloaded the DEM file from

ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM30/e020n40

and:

- Using the DEM to Raster tool in my copy of ArcCatalog 9.1 gives me a "corrupt input file" error message.
- Trying to open the DEM in MicroDEM give me an "unacceptable DEM" error message.

I browsed over to the "version1" files and got the same result.

hmmm...

[Charlie Frye]

As Brian poinited out: you need to download the header file as well (.hdr). While you're at it get the PRJ file and you your day will go even better.

ArcGIS 9.2 reads this data natively, no conversion needed.

[Cartisan Maps]

Charlie, I've got the hdr and prj files, in the same directory. When I grabbed the data it all came nicely compressed together for me. This applies for the files that did import correctly, as well as the files that did not.

Brody.

[Andrew]

Hi all,

Just wanted to add a site where I have been getting my SRTM data from. I download the tiles I want as a GeoTiff and then load them seamlessly into ArcMap. So far I have experienced no problems, and its actually quite easy.

I must add though the data is only the SRTM 90 metre product, which is the best we can get down here.

CGIAR-SRTM downloads

Hope someone finds this useful.
Andrew

[Charlie Frye]

Charlie, I've got the hdr and prj files, in the same directory. When I grabbed the data it all came nicely compressed together for me. This applies for the files that did import correctly, as well as the files that did not.

Sounds like some the data's corrupted--lost packets on transmission or it may have been corrupted when it was created. You'll have to check with the data provider--though they'll usually ask if you tried downloading it again just to verify that it was not a download issue (check the file sizes, etc.). If that doesn't work, see if anybody else has been successful with that dataset. Or, like Andrew suggests find another provider who has the same data.

[Cartisan Maps]

The CGIAR SRTM data works just fine, and it is accessible via FTP (link in an earlier post in this thread). The only difference being much larger file sizes and Version 3, as opposed to Version 2 on NASA's site.

The other SRTM distribution sites I've come across either feet back to the NASA FTP site, or in the case of the GLCF ESDI, serve v3 data. I was hoping to compare the two versions before jumping into v3, but the specific tile I'd like to use is one of the corrupted ones. But, since v3 works, and is billed as being better than v2...it'll work for me.

Brody.

[Martin Gamache]

Note that there are some significant differences between the CGIARS data and the data sitting at JPL.

CGIARS has run some correction and patching on their data and was (at least in its early version ) based on the 1st SRTM data release.

From the JPL FTP site you can pull down version 2 SRTM data which has had some patching done and flat water areas/coastlines fixed.

My preference is for the version 2 rather than CGIARS after doing some non scientific comaprisons over some rugged areas. I'd rather do the patching myself and have better control over the process.

IMO just finding another source doe snot necessarily mean you are getting the same dataset.

Being able to read this SRTM data in natively may be worth upgrading to 9.2 for me.


mg

[Matthew Hampton]

The CGIAR data is now Version 3.

[MaryLynne]

I've been following this thread and decided to take a closer look at the SRTM data now that I just upgraded to 9.2. Perhaps someone has some suggestions on how to create a hillshade that looks like the .gif that is delivered with the data. The default hillshade I created looks pretty poor.

Thank you.

Mary Lackner

[Matthew Hampton]

The data is in decimal degrees - so in Spatial Analyst-->Surface Analysis-->Hillshade... the Z factor should be set to .0001 (or something close) instead of the default "1."

It makes quite a difference!