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

Mon Jun 11 09:20:15 EDT 2012

Hello,

I have tried with the approach given below by Angelo, but I could not
succeed. I get a tif file after using set gxout kml, but when I try to
convert this file via gdal_translate, my result still stays in
latlon-projection.

Can anyone help me on how to go from geotiffs to pngs in mercator
projection? Thanks!

Jonas

On Wed, Jun 6, 2012 at 11:53 AM, Jonas Kaufmann <me at j0nes.de> wrote:
> Hello Angelo,
>
> thank you for your help! Would the resulting ctl file in my case (GFS
> 0.5 degrees) look like this then?
>
> xdef 720 levels 0 0.5 1 1.5 (etc)
> ydef 360 levels -90 -89.5 -89 (etc)
>
> Thanks again for your help!
>
> Best regards,
>
> Jonas
>
> On Tue, Jun 5, 2012 at 6:16 PM, Angelo Bertozzi
> <angelo.bertozzi at meteocenter.it> wrote:
>> hi
>> I've a method for producing map overlay with Grads in mercator projection,
>> but is not so straightforward
>>
>> i'm starting from rotated lat-lon or lambert conformal preprojected data in
>> grib files
>> 1) remove pdef directives in ctl files and sobstitute the "linear"
>> progression in xdef and ydef with "levels" directive with the list of
>> latitudes (ydef) and longitudes (xdef) of any single grid nodes
>> This steps in my case is producing a huge .ctl files (the grib ctl files
>> describing a 1600x2000 grid); a perl text-manipulation script is doing this
>> work
>> 2) plot a tiff image with "set gxout kml",
>> 3) converting and rescaling with imagemagick the *tiff image in PNG
>>
>>
>>
>>
>> 2012/6/5 Jonas Kaufmann <me at j0nes.de>
>>>
>>> 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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>>
>>
>>
>> --
>> ------------------------------------------------------------------------
>> Bertozzi Angelo
>> Meteorologist - HPCC admin & research
>> Atmospheric and Environmental numerical modeling division - head
>> Mobile 345-71.335.07 - Office 0546-046207
>> METEOCENTER (Sms Srl)
>> Parco delle Arti e delle Scienze "TORRICELLI" - Via Albert Einstein, 8 -
>> 48018 FAENZA (RA) - ITALY
>>
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