[ gpsdrive ] grib files

[Hamish]

Chris H wrote:
> I started exploring the possibility of including grib file (weather 
> data) that is freely available on line.
....
> It appears that gdal_translate has the capability of converting NetCDF
> files to geotiff.

NetCDF is a bit complex, but things look rather good in GDAL-land:
  http://www.gdal.org/frmt_grib.html


> Now since gdal is used to prepare NOAA charts for example the same
> program could in theory convert, converted grib files via the
> process described above...theoretically of course.

sure, presumably this is mostly useful at continental map scales?

> The only part that is not known to me is if gpsdrive could
> overlay the grib files over the geo referenced chart tiles??

you would have to overlay the data upon processing the GRIB NetCDF.
NetPBM offers a tool for that, we use a similar method in GRASS to overlay the map and decoration layers for display in the GUI window. It's pretty straight forward as long as the GRIB data is suitable for transparency.

for updates keep your map.koords table the same and replace the gpsdrive
map tiles (preserving filename). (or replace map dir and koords file together)  .. I don't know about gpsdrive tile caching, maybe there is a problem there.


> Just wondering as it would be a nice addition for marine use and grib
> files are free. See saildocs.com if interested.  If it was possible
> it would be a rather elegant solution for dealing with weather when
> gpsdrive is used for marine applications. 

the only thing I worry about is how to ensure the tiles are up to date? use netpbm tool to overlay a watermark timestamp in the top left of each tile??


I'll put it on my virtual list of things to look at once I get back from away; if no one else gets to it first.


regards
Hamish