[gdal-dev] A strange thing with a png geospatial file and gdalwarp. Is it a bug?
aborruso
aborruso at gmail.com
Wed Sep 4 01:51:25 PDT 2013
Dear all,
I have a geospatial png file - http://ge.tt/7tmMR7r/v/0?c -and gdalinfo give
me this projection info:
PROJCS["Popular Visualisation CRS / Mercator",
GEOGCS["Popular Visualisation CRS",
DATUM["Popular_Visualisation_Datum",
SPHEROID["Popular Visualisation Sphere",6378137,0,
AUTHORITY["EPSG","7059"]],
TOWGS84[0,0,0,0,0,0,0],
AUTHORITY["EPSG","6055"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.01745329251994328,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4055"]],
UNIT["metre",1,
AUTHORITY["EPSG","9001"]],
PROJECTION["Mercator_1SP"],
PARAMETER["central_meridian",0],
PARAMETER["scale_factor",1],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
AUTHORITY["EPSG","3785"],
AXIS["X",EAST],
AXIS["Y",NORTH]]
It's EPSG:3785.
If I run this command:
gdalwarp -s_srs EPSG:3785 -t_srs EPSG:4326 -of GTiff "input.png"
"output.tif"
The output file has this extent:
Upper Left ( -0.6064394, 44.7016078) ( 0d36'23.18"W, 44d42' 5.79"N)
Lower Left ( -0.6064394, 44.6980730) ( 0d36'23.18"W, 44d41'53.06"N)
Upper Right ( -0.5975973, 44.7016078) ( 0d35'51.35"W, 44d42' 5.79"N)
Lower Right ( -0.5975973, 44.6980730) ( 0d35'51.35"W, 44d41'53.06"N)
Center ( -0.6020184, 44.6998404) ( 0d36' 7.27"W, 44d41'59.43"N)
If I run this command, without -s_srs parameter:
gdalwarp -t_srs EPSG:4326 -of GTiff "Avenue de Mont-de-Marsan.png"
"male.tif"
This output has an extent that is different from the previous (look at
latitude):
Upper Left ( -0.6064394, 44.8937072) ( 0d36'23.18"W, 44d53'37.35"N)
Lower Left ( -0.6064394, 44.8901724) ( 0d36'23.18"W, 44d53'24.62"N)
Upper Right ( -0.5975973, 44.8937072) ( 0d35'51.35"W, 44d53'37.35"N)
Lower Right ( -0.5975973, 44.8901724) ( 0d35'51.35"W, 44d53'24.62"N)
Center ( -0.6020183, 44.8919398) ( 0d36' 7.27"W, 44d53'30.98"N)
Is it normal?
I'm using GDAL 1.10.1, released 2013/08/26, downloaded from here
http://vbkto.dyndns.org/sdk/.
Thank you,
Andrea
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