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api.geonames.org/srtm3? incorrect values for coordinates with elevations below MSL  XML
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jooppeek



Joined: 09/04/2010 08:09:20
Messages: 8
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Hello Marc,
It seems that srtm3 does not return correct values for coordinates which have elevations below MSL. E.g. Lelystad Airport in the Netherlands(http://ws.geonames.org/srtm3XML?lat=52.46&lng=5.53) returns 251, but should be approx. -4m (-13feet)
Could you please reply what is wrong, or what I'm doing wrong.
Thank you very much,
Joop
marc



Joined: 08/12/2005 07:39:47
Messages: 3762
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Hi Joop

This seems to be wrong indeed. I don't know what is wrong, it could be that the srtm data production process has issues with this area.

Best Regards

Marc

[WWW]
jooppeek



Joined: 09/04/2010 08:09:20
Messages: 8
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Hello Marc,
It is still not working for below MSL coordinates. Is there anyone you or I could address?
Best regards,
Joop
marc



Joined: 08/12/2005 07:39:47
Messages: 3762
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Well, there is no fast solution. The data is from NASA with improvements made by CGIAR:
http://geonames.wordpress.com/2012/02/20/improved-srtm-digital-elevation-data/

Building new satellites, sending them to orbit etc will take some time ...


Best Regards

Marc

[WWW]
jooppeek



Joined: 09/04/2010 08:09:20
Messages: 8
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Hello Marc,
I cannot open the link you posted.

It's strange that the service now returns incorrect below MSL altitudes, because I used it quite extensively a couple of years ago (2009/2010) and then it worked perfectly.

Well, I'm using it not very extensively for the Netherlands anymore, so I'll survive
Thanks for your effort and replies.

Regards,
Joop
jooppeek



Joined: 09/04/2010 08:09:20
Messages: 8
Offline

Hello Marc,
In previous mail I said that your link wasn't working. Disregard this remark. There was something wrong with my internet connection, and the link is ok.
Regards,
Joop
marc



Joined: 08/12/2005 07:39:47
Messages: 3762
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You are right. The previous srtm data version has negative elevation at this position

http://api.geonames.org/srtm3XML?lat=52.46&lng=5.53&source=srtm3&username=demo

It looks like an error in the improved version.

Best Regards

Marc

[WWW]
marc



Joined: 08/12/2005 07:39:47
Messages: 3762
Offline

Update:

It turned out to be an error in the processing of the raw data. The error has been fixed, the data reprocessed and redeployed to all servers.

Best Regards

Marc

[WWW]
 
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