| GeoTIFF help - conversion to lat/lon [message #94512] |
Fri, 16 June 2017 01:32  |
rjp23
Messages: 97
Registered: June 2010
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Member |
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I'm hoping someone can help as the GeoTIFF format is confusing me somewhat.
I'm following David's excellent tutorial at http://www.idlcoyote.com/map_tips/tiffoverlay.html
However, my GeoTIFF is missing some of the geotag information that David uses in his example.
I don't have the variables to do this bit:
; Map the corners in lat/lon space by inverse transformation.
alberMap = MAP_PROJ_INIT('Albers Equal Area Conic', $
DATUM=8, $ ; WGS84
CENTER_LAT=geotag.PROJNATORIGINLATGEOKEY, $
CENTER_LON=geotag.PROJNATORIGINLONGGEOKEY, $
STANDARD_PAR1=geotag.PROJSTDPARALLEL1GEOKEY, $
STANDARD_PAR2=geotag.PROJSTDPARALLEL2GEOKEY)
lonlat = MAP_PROJ_INVERSE([xOrigin, xOrigin, xEnd, xEnd], $
[yOrigin, yEnd, yEnd, yOrigin], $
MAP_STRUCTURE=alberMap)
And I can't work out what the equivalent is with what I have:
IDL> help, geotag
** Structure <637638>, 18 tags, length=184, data length=158, refs=1:
MODELPIXELSCALETAG
DOUBLE Array[3]
MODELTIEPOINTTAG
DOUBLE Array[6, 1]
GTMODELTYPEGEOKEY
INT 1
GTRASTERTYPEGEOKEY
INT 1
GTCITATIONGEOKEY
STRING 'Projected Coordinates |'
GEOGRAPHICTYPEGEOKEY
INT 4326
GEOGCITATIONGEOKEY
STRING 'WGS84'
GEOGGEODETICDATUMGEOKEY
INT 6326
GEOGPRIMEMERIDIANGEOKEY
INT 8901
GEOGLINEARUNITSGEOKEY
INT 9001
GEOGANGULARUNITSGEOKEY
INT 9102
GEOGELLIPSOIDGEOKEY
INT 7030
GEOGSEMIMAJORAXISGEOKEY
DOUBLE 6378137.0
GEOGSEMIMINORAXISGEOKEY
DOUBLE 6356752.3
PROJECTEDCSTYPEGEOKEY
INT 32611
PCSCITATIONGEOKEY
STRING 'UTM / WGS84'
PROJECTIONGEOKEY
INT 16011
PROJLINEARUNITSGEOKEY
INT 9001
Also listgeo doesn't seem to exist at https://www.remotesensing.org/geotiff/listgeo.html any more.
Any help would be much appreciated
Thanks
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| Re: GeoTIFF help - conversion to lat/lon [message #94568 is a reply to message #94550] |
Tue, 11 July 2017 10:58  |
gombgg
Messages: 7
Registered: November 2013
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Junior Member |
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On Sunday, July 2, 2017 at 7:28:50 AM UTC-6, rj...@le.ac.uk wrote:
> On Monday, June 26, 2017 at 11:55:38 PM UTC+1, gom...@gmail.com wrote:
>> You probably found your answer by now, but your data appears to be using the UTM coordinate system, which is different than Lat/Lon. You'll need to convert your UTM coordinates to Lat/Lon first if you need to use that coordinate system.
>
> Thanks! I'm still struggling to get this right so if you could point me in the right direction that'd be great.
Something like this should come up on a search:
http://www.idlcoyote.com/map_tips/convertutm.php
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