HGT update

Ingo Rau shared this question 4 months ago
Answered

Is it possible to update HGT files with Locus? Are they updated at all? Or are there different sources for some countries with better resolution, and newer?

I was glacier trekking last week in Switzerland, and sometimes the actual altitude was more than 100m (!) below what Locus was showing me.

I realize that for probably 99.9% of the earth's surface, the altitude profile doesn't change significantly over the years - but glaciers are an exception, and unfortunately these days a big one.

Anyone knows anything about this?

Comments (10)

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Hi,

we use several free sources for elevation HGT data. For Austria, Slovenia and part of Germany we use elevation data from Local Lidar missions but the main part of data is from Viewfinderpanoramas project. ViewFinderPanorames used also several datasources to obtain the most precise digital elevation model. It seems that majority of data it's from years 2000 or 2009. I'm sorry but we can't provide newest data.


I know that global warming is here but I wouldn't expect such changes. Please check your settings Menu > Settings > GPS and location > Altitude correction > enable "Altitude offset" and "Automatic correction" on Offset tab. This settings correct elevation from GPS to "real" values. Please see http://docs.locusmap.eu/doku.php?id=manual:user_guide:tools:altitude#altitude_offset


Thank you

Best regards

Petr

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Hi guys,

Peter, I should be careful with "wouldn't expect". For example here is clearly "First results from field measurements indicate that the extreme warm and dry weather conditions in summer 2003 caused an average loss in thickness of glaciers in the European Alps of about 3 meters water equivalent, nearly twice as much as during the previous record year of 1998 (1.6 m), and roughly five times more than the average loss of 0.65 m per year recorded during the exceptionally warm period 1980 - 2000. In 2003 alone, the total glacier volume loss in the Alps corresponds to 5-10% of the remaining ice volume (18).".

So since year 2000, total change of glacier height may be even close to 50 metres. Just for your info ...

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Thx for the explanation. I'm in Switzerland btw - what data do you use there?

However, it's not a matter of settings - we crosschecked the data with several separate altitude meters on several days, always calibrating it at the last fixed point. So yes, sad but true, but some glaciers can lose more than 100m of height within a decade or two (if you're interested: It's the Gornerglacier in Zermatt). The finding is also confirmed by our mountain guide that has been doing this route for more than 20 years...

Anyway, I just thought because I have the HGT files cached on my phone: Does Locus ever checked for updates at all (if there are any)? I could probably force an update by deleting the file, sure, but that's tedious...

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Because I'm not aware of any news in HGT files on Petr's side ( on server ), Locus Map itself ( my side ) do not check for any news in HGT files for now.

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Hi,

thank you for info. I really didn't expect that it's possible to loose 100m in one decade.

However to your question. Locus does not check for updates of HGT files because there are no updates or are very rare. Basically we changed only files for Austria and Slovenia (mentioned Lidar mission) during last 4 years. I'm not sure but I think that there aren't any new (free) data sources we could use for update.

It's seems that Swisstopo provides swissALTI3D elevation dataset updated in an cycle of 6 years but the data are quite expensive.

Petr

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Just so there's no wrong impression: The 100m was of course a maximum - a glacier looses mass very differently at different locations depending on a lot of factors. Menion's 50m is probably a better value to work with as average - which of course includes locations with 100m loss.

Anyway, thx for clearing up my understanding of the HGT files (now I know that it's no use deleting them manually).

Last question: If I bought (if that's possible) the swissALTI3D data, would I be able to use it in Locus or is HGT not a standard format?

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Hi,

I'm sorry for the late response (I've overlooked the last post). The conversion would be very likely possible. I think that conversion is possible with qGIS and gdal_translate or gdal2xyz module. Honestly I didn't try it but hgt is known format and gdal should support it.

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OK, thx. Will try if I decide to get the data (and can get a hand on it ;).

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Uh-uh, I checked it out - those swissALTI3D are much too expensive for normal people...

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Yes, it is. I don't know if there is any alternative for Switzerland. Please let me know if you find some useful and free dataset.

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