[Gdal-dev] Warping Plate Carree images to Mercator

[Robert Rose]

On Jun 2, 2006, at 7:13 AM, Lennox Antoine wrote:

> I believe this is the same projection used in VirtualEarth
> (http://local.live.com/default.aspx? 
> v=2&cp=0~0&style=h&lvl=1&scene=1875974),
> so you can check out the projection they used to get it into
> Geographic LL coordinates.
>
> http://www.brains-n-brawn.com/default.aspx?vDir=veworldwind
>
> I'll paste the reprojection area of the code here :
>
> //NOTE tiles did not line up properly with ellps=WGS84
> //string [] projectionParameters = new string[]{"proj=merc",
> "ellps=WGS84", "no.defs"};
> //+proj=longlat +ellps=sphere +a=6370997.0 +es=0.0
> string [] projectionParameters = new string[]{"proj=merc",
> "ellps=sphere", "a=" + earthRadius.ToString(), "es=0.0", "no.defs"};
> proj = new Projection(projectionParameters);
>
> I have also had luck estimating it with tangent and log functions
> without using proj.4.

Hi Lennox, thanks for the response.

I'm not sure how to turn what you've given me into command line  
parameters for gdalwarp or gdaltranslate tho...  The Mercator  
projection string sounds pretty similar to what I was trying before...

1) Save http://veimages.gsfc.nasa.gov/7107/world.topo.bathy. 
200408.3x5400x2700.jpg as world.jpg..

2) gdal_translate -a_srs EPSG:32662 -gcp 0 0 -180 90 -gcp 5400 0 180  
90 -gcp 5400 2700 180 -90 world.jpg world.tif

3) gdalwarp -s_srs EPSG:32662 -t_srs "+proj=merc +datum=WGS84" -ts  
512 512 world.tif worldm.tif

(EPSG:32662 is the projection code for WGS84 Plate Carree)

So are you suggesting I add "+ellps=sphere", "es=0" and  
"+a=earthRadius" to my gdalwarp command?

-robert
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