On 6/13/12 10:00 AM, gdal-dev-requ...@lists.osgeo.org wrote
David Hoese wrote
>
> I'm attempting to project satellite data to an AWIPS grid. Assuming I
> have the grid defined correctly with proj4 parameters, I've been using
> "+proj=latlong +datum=wgs84" as my s_srs parameters. Does that sound
> correct for satellite data? So my command line call (still for testing)
> becomes:
>
Is it publicly available satellite data? I will give it a go myself if i
have some sample data.
I'm not sure at the moment, it's VIIRS data. I'm playing around with
different existing remapping tools, I have one that works called
ms2gt(ll2cr/fornav) which you might be able to google for the old
versions, but it's slightly outdated and is single purpose. I would
like to use GDAL if it can handle it, because of the various formats
that it supports as output.
David Hoese wrote
>
> gdalwarp -s_srs "+proj=latlong +datum=wgs84" \
> -te 59.844 -123.044 14.335 -65.091 \
> -ts 5120 5120 \
> -t_srs "+proj=lcc +lon_1=-95.000 +lon_0=-113.133 +lat_2=25.0001
> +lat_1=24.9999 +lat_0=16.369" \
> -geoloc -of GTIFF \
> image.vrt out.tif
>
> The output grid is 5120x5120 and I wasn't sure if -te was lat/lon
> points, but that's what I used. -te has lat/lon of upper left pixel of
> the grid and lat/lon of the lower right pixel of the grid. Does any of
> this look correct? Thanks for the help.
>
Geographic WGS84 (lat/lon) is an obvious choice if you're not sure, but its
not necessarily correct. As you can see, your Lambert target projection has
coordinates in a similar value range, so you cannot be sure just based on
the values alone.
The syntax for gdalwarp seems alright to me. Because you're outputting to a
rather large area (geographically), it might be useful to test it for a
small subset first to rule out difficulties in finding a proper
transformation, although im not sure if it could help in this case.
So I've played around with this for a while now and have gotten
somewhere. I was able to get data into the geotiff, but with a lot of
guess work and small tweaking. My t_srs is now:
"+a=6378137 +lon_1=-95.000 +b=6356752.314 +lon_0=-123.044 +proj=lcc
+lat_1=25.000 +lat_0=59.844 +ellps=WGS84 +no_defs +wktext +units=m"
All of which are probably not necessary, but at this point it doesn't
hurt. The origin in that projection is the upper left corner of my
grid. So I now specify -te as something like:
"-te 0.0 -5120000.0 5120000.0 0.0"
Which gets me something in the geotiff. I've played around with
different extents and my best result comes from me manually changing the
extents to match a picture I have from another system. The grid I'm
trying to match to is the first one on this page:
http://www.nws.noaa.gov/noaaport/html/icdtb48_2.html
I have tried using pyproj and plugging in different corner points to get
the extent points in meters, but when I use those I get skewed images
(the grid should be 5120 x 5120).
So at this point, I just need to find a way to get the extents figured
out in a programmatic way (like 1km * 5120 grid pixels = 5120000
meters). If you have any more advice that'd be great, otherwise I'll
just have to keep playing around and asking people around my work.
Thanks a lot for the help so far.
-Dave
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