[gradsusr] Generating image overlay for Open Street Map / Mercator Projection

[Jonas Kaufmann]

Hello,

thank you for your answer! Too bad there is no support for Mercator
projection available (yet).

I just had a look at the GeoTIFF output, but I did not succeed in
creating a PNG (or whatever) file that I could overlay on OSM or
Google Maps. The tif file gets created, but it is looking almost
completely black when viewing with an image viewer (but I think this
is expected behaviour?). I have tried to convert it to PNG using the
GDAL tools with gdal_translate, but I only get grayscale noise images.

Can someone explain the correct workflow to go from 'set gxout
geotiff' to a displayable PNG image?

Thank you for your help!


Jonas


On Thu, May 31, 2012 at 5:05 PM, Chris Slocum
<cslocum at atmos.colostate.edu> wrote:
> Hi Jonas,
>
> I too have been looking for a Mercator projection to
> use with something like Open Street Map. To date,
> I do not think there is a public extension for a Mercator
> projection but the idea has been bounced around.
>
> I know that Weather Underground had someone
> develop the projection for their WunderMap so it
> is possible to do.
>
> In the interim, you could look at the GeoTIFF option.
>
> -Chris
>
>
>
> On Thu, May 31, 2012 at 6:46 AM, Jonas Kaufmann <me at j0nes.de> wrote:
>>
>> Hello,
>>
>> I am trying to generate an image with GrADS that should cover the
>> whole world. The image should be based on an forecast from the GFS
>> model. I want to use this image as a layer on top of Open Street Map.
>>
>> I can already create an image without borders, labels etc that I can
>> put on my map. However it seems that the projection still is wrong,
>> e.g. the continent borders drawn by GrADS do not match the borders on
>> the map. I think this might be related to the map projection used, in
>> OSM this should be Mercator projection which is not available in
>> GrADS. The complete script can be found at the bottom of the mail.
>>
>> Is there a way to make the forecast map fit on OSM?
>>
>>
>> Thank you for your help!
>>
>>
>> Jonas
>>
>>
>> -------
>>
>> 'open gfs'
>>
>> 'set gxout shaded'
>> 'set parea 0 11 0 8.5'
>> 'set mpdraw off'
>> 'set frame off'
>> 'set xlab off'
>> 'set ylab off'
>> 'set mproj latlon'
>> 'set grads off'
>>
>> 'set mpdset hires'
>> 'set map 1 1 1'
>>
>> 'set lon -180 180'
>> 'set lat -90 90'
>>
>> 'd mag(ugrd10m, vgrd10m)'
>>
>> 'printim world.png x512 y512'
>> 'quit'
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>
>
>
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