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

[Jonas Kaufmann]

Hello,

do you have an idea how to use 'set gxout geotiff' to generate
displayable PNG images for use on a map software? Or do you have any
other hints how Mercator projection in GrADS works?

Thank you for your help!

Jonas

On Fri, Jun 1, 2012 at 10:55 AM, Jonas Kaufmann <me at j0nes.de> wrote:
> 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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