[gdal-dev] Geostationary Projection with microradians

[Even Rouault]

On mercredi 8 mars 2017 14:55:36 CET Zachary Flamig wrote:
> Hi all,
> 
> The GOES-16 satellite has started delivering full disk netcdf files that
> conform to a new portion of the CF standard:
> https://cf-trac.llnl.gov/trac/ticket/72
> <https://cf-trac.llnl.gov/trac/ticket/72> Unfortunately, they choose to use
> units of micro-radians instead of meters so it doesn’t appear the files are
> immediately compatible with GDAL.
> 
> It is rather straight forward to convert from the radians to meters given
> the height of the satellite (which is included in the projection
> information). Would this be something appropriate for GDAL to convert or is
> it more of a PROJ4 problem?

I don't pretend to have a very well informed opinion on the GEOS projection, but if you can 
fix that in GDAL and do the conversion from microradians to meters it seems reasonable. 
Projection support in WKT and proj.4 assumes that the units of x, y values are linear (meter, 
feet, etc...), so dealing with angular units would probably be complicated at that level. 
Especially since the conversion from microradians to meters depend on another parameter 
(height of the satellite). So a fix in the netCDF driver would seem OK to me. 

> 
> I’ve uploaded some example netcdfs here:
> https://www.dropbox.com/s/ell4iy0hiwzquqy/fulldisk_wv.zip?dl=0
> <https://www.dropbox.com/s/ell4iy0hiwzquqy/fulldisk_wv.zip?dl=0> The data
> is tiled into 4 separate netcdfs that can be combine for the full disk
> image.
> 
> Cheers,
> Zac


-- 
Spatialys - Geospatial professional services
http://www.spatialys.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20170308/de82ed68/attachment.html>