An easy way to do this is to convert the PGM to GeoTIFF using the
"gdal_translate" tool that is part of FWTOOLS:
http://fwtools.maptools.org/
gdal_translate -a_srs EPSG:4326 -a_ullr -180 -35 180 35
SeaWiFS_median_depth.35N.35S.180W.180E.pgm SeaWiFS_geotiff.tif
This took about 5 seconds on my intel pc.
Then you can visualize it (instantly) using the OpenEV viewer that
comes with FWTOOLS, or visualize it in IDV (I think, since IDV handles
GeoTIFF)
-Rich
On 9/6/06, Don Murray <dmurray@xxxxxxxxxxxxxxxx> wrote:
Hi Valentijn-
Valentijn Venus wrote:
> i'm looking for a utility developed by Unidata in the days of Ynot:
> pgmtonc
>
> This utility takes an image in the Portable Gray Map intermediate
> format and writes it to a netCDF file. I would like to convert a
> shallow waterdepth product from SeaWIFS into a netCDF file to be able
> to display and use it in the IDV.
>
> coral reefs shallow waterdepths from SeaWIFS:
> ftp://ocdist5.sci.gsfc.nasa.gov/pub/seawifs_bathymetry/README
>
> pgmtonc: see
> http://www.unidata.ucar.edu/newsletter/1993spr/93sprel.html#article6
>
> quote:
>
> Pbmplus utilities you can get them via anonymous ftp from
> ftp.unidata.ucar.edu in the file pub/pbmplus.tar.Z. This compressed
> tar file contains all of the Pbmplus utilities, including pgmtonc.
> Or, you can FTP it from the contrib directory in the Ynot
> distribution account (this will only work if you are a licensed Ynot
> user). The file name is pgmtonc.tar.Z. To build the Pbmplus
> utilities, you will need the various Pbmplus libraries included in
> the tar file, as well as the netCDF library.
Even if you had this file, you'd still need to add in navigation
information since that is not in the file.
> Unfortunately, it's no longer on the server. Any ideas/other
> solutions?
You could take the PPM version and convert it to a GIF and
then read it into the IDV and use the Navigated Image formula.
However, if I uncompress the PPM file, it's 756 Mb. I used
ppmtogif to create a GIF which was 103 Mb (36000x7000 pixels).
You could subsample the navigated image with the following
Jython:
def skip(image, skip):
from ucar.unidata.data.grid import GridUtil
return GridUtil.subset(image, int(skip))
and have your formula be:
skip(image, numpts[isuser=true])
which would prompt you for the number of points. I used 100
and displayed it with a Color Shaded Plan view which produced
a blocky image.
By comparison, on my Windows system, it took the Windows Fax
and Picture viewer about 10 minutes to generate the preview of
the full image.
Don
*************************************************************
Don Murray UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx P.O. Box 3000
(303) 497-8628 Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************
--
Dr. Richard P. Signell (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598
