Using digital elevation models in position estimation

[giaminhhoang]

Hello,
In GNSS position estimation, known altitude is useful to improve the accuracy or constraint the results, and I found that your algorithm is using it. I am wondering how can you compile the *.hgt files in /digital_elevation_model to a full egm96-5.pgm 2-D map. I guess to have the full map, the number of *.hgt files should be more.
Could you share some insights?
Thanks a lot.
Best.

[JonasBchrt]

That's correct.
You can download more .hgt files from here: https://e4ftl01.cr.usgs.gov/MEASURES/SRTMGL1.003/2000.02.11/
The ones in the repository cover just Oxford.

Alternatively, use ETOPO1 for global coverage.

(More details in the doc string of eph_util.get_elevation(...):

snapshot-gnss-algorithms/eph_util.py

Line 3545 in 422d679

def get_elevation(latitude, longitude, model='ETOPO1', geoid='egm96-5'):

)

Does this help?

[giaminhhoang]

Thanks Jonas. It helps a lot.

[giaminhhoang]

Though the global coverage of ETOPO1 is quite interesting, its 1-arc minute resolution is not enough for my study. So I have to come back to SRTM 1 Arc-Second. The link you provided to download .hgt files for this model while https://earthexplorer.usgs.gov/ gives only dted, bil or GeoTIFF formats. But I understood that they come from the same SRTM.
Do you know which one I should use? Thanks in advance.

[JonasBchrt]

I used the .hgt files because they are supported by the python-srtm package.
I believe DTED and GeoTIFF should be able to store the same information. (Don't know about BIL.) There are Python packages for those formats, too. (If Python is your language of choice.) They might differ in file size, though. I believe I have also seen converters for those file types out there.

[giaminhhoang]

Thanks a lot for your quick reply. I am using Matlab and just founding this project using Matlab to read the .hgt file https://fr.mathworks.com/matlabcentral/fileexchange/36379-readhgt-import-download-nasa-srtm-data-files-hgt.