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[Paparazzi-devel] Re: utm


From: Pascal Brisset
Subject: [Paparazzi-devel] Re: utm
Date: Wed, 18 Apr 2007 11:36:08 +0200
User-agent: Icedove 1.5.0.10 (X11/20070329)

Hi Martin,

UTM coordinates are not used for SRTM: the SRTM files are aligned of geographic (lat, long) coordinates. Unfortunately, data are missing for Norway, north of latitude 60° (see for example, http://www.caf.dlr.de/dlr/presse/archiv/sonderseiten/srtm/coverage.htm).

But, ..., I found another source

   http://www.viewfinderpanoramas.org/dem3.html

where the provided P31.zip contains the desired N60E005.hgt (now available from
www.recherche.enac.fr/~brisset/N60E005.hgt.bz2 )

It seems almost correct (well the sea surface is about 15m in the harbour !) and anyway should be enough for
the GCS.

--Pascal

PS: By the way, some other awfull problems are hidden behind UTM coordinates usage in Paparazzi ...


Martin Mueller wrote:
Hi Pascal,

there is some strange thing we saw. We did some simulations for eastern Norway 
where the meteo guys from University of Bergen live. They are in Hildesheim 
right now and think about using Paparazzi for measurement (we met Prof. Reuder 
outside the Braunschweig building before going to DLR last summer, he started 
the EU COST paper work).

We did a flight plan for Bergen (N 60.382817 E 5.330858) and loaded the SRTM. 
There is no SRTM info in the GCS for Bergen area, it shows 32768m. If you turn 
on the UTM grid on in GCS and walk south with the mouse, it will appear at some 
UTM grid border. I remembered some strange UTM behaviour and saw that 
http://www.dmap.co.uk/utmworld.htm

In eastern Norway and Svalbard (which is intersting to them...) the grid is 
different http://www.fmnh.helsinki.fi/english/botany/afe/map/utm.htm

Most UTM converters are not aware of that and give grid 31 for the region. This 
one seems to do it http://www.dmap.co.uk/ll2tm.htm If you enter values around 
the borders (e.g. N 56'0 E 5'0 and 55'59 E 5'0) you will have another grid and 
a different eastern reading as it starts at a different longitude.

Could it be that this utm "anomaly" makes the SRTM go away?

See you,
Martin
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