Hi,
A couple of things,
1. Planar world is not 44.000.000 meters wide. It follows from the meter
definitions that it is 40 000 000 meters
2. Mercator maps cannot span to +/- 90 degrees latitude
3. The images in www.oera.net/How2/TextureMaps2.htm are not Mecator
4. and changing something like 179.12345 to 180.0 . You should not do that.
Coordinates in the world file are that of the CENTER of the top left pixel
5. The whole thing was easy task with Mirone.
I used the first image on that page and with it just do:
Put this inside a file named EarthMap_2500x1250.jgw
0.144000
0.0
0.0
-0.144000
-179.928000
89.928000
and now
gdalwarp EarthMap_2500x1250.jpg -s_srs +proj=latlong -t_srs +proj=laea
EarthMap_2500x1250.jpg dest.jpg
Which will show ... another manifestation of the gdalwarp bug
(http://trac.osgeo.org/gdal/ticket/2305)
when dealing with global files
Joaquim Luis
I tried georeferencing one of these images ( http://www.oera.net/How2/TextureMaps2.htm ) using
MapWindow GIS; the pogram generated a .jgw file, which then I fixed by replacing , by
. and changing something like 179.12345 to 180.0 .
Then I tried again this command:
gdalwarp -s_srs +proj=merc -t_srs +proj=laea world.jpg dest.jpg
Ok, program now does not complain for any error... but what I get as output is
EXACTLY the SAME image!!!
What's wrong now?
And how do I specify the center of the Lambert projection to be on north pole?
*** BEGIN FORWARDED MESSAGE ***
On 09/02/2009 at 13.47 jumpjack jumpj...@libero.it wrote:
From: jumpjack jumpj...@libero.it
To: Wendy Fay Stevenson steve...@erau.edu
CC: gdal-dev@lists.osgeo.org
Date: Tue, 10 Feb 2009 18:48:45 +0100
Subject: Re[4]: [gdal-dev] gdalwarp: mercator to lambert azimutal equeal area
Thanks, but I can't yet understand...
I have a map of the whole world. It is 640 pixel wide. Planar world is
44.000.000 meters wide so which number should I specify as A??
The same applies for E.
About C and F: which coordinates should I specify? Lat and Lon? This
would be 90,-180, I guess, being the map centered on Lat,Lon=0,0 and 360°
wide and 180° tall.
Thanks for your pacience.
(Please reply on the list, others could be interested!)
bye,
Jumpjack
*** REPLY SEPARATOR ***
On 09/02/2009 at 13.47 Wendy Fay Stevenson wrote:
As long as the world file is the same name as the input file to gdalwarp,
it will work.
As for specifying the world file:
A: number of meters across / number of pixels across
D B: 0
E: -1 * number of meters in length / number of pixels in length
C and F specify the center of the top left pixel in eastings and
northings, i.e. where on the projection the first pixel corresponds to.
*** END FORWARDED MESSAGE ***
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