[gradsusr] NWS NDFD grids and GRADS

[Jennifer Adams]

Wayne --
Without knowing what "asciigrid" is doing, it's hard to say what the  
problem might be. Have you tried to export the data as a geotiff and  
importing that into GRASS? Also, you should try to find an NDFD  
variable such as land mask that would have recognizable non- 
meteorological features in the data -- then you could reliably point  
to the data set that has the bad navigation, either in your GrADS  
descriptor or in your ascii output.
--Jennifer


On Oct 5, 2010, at 5:29 PM, Wayne Gibson wrote:

>   In attempting to use the temperature National Digital Forecast Grids
> (NDFD) with GRADS, I've found some unexpected results.  If I export  
> the
> grids to ASCII format and read them into another GIS package (GRASS),
> the temperature minimum at a location near Las Vegas are shifted in
> space  westward into California.  The original NDFD grids are in  
> Lambert
> projection GRIB2 format.
>
> My steps are
>
> 1) create GRADS control file using g2ctl.pl
> 2) Created index file using gribmap
> 3) Run Grads
>
> open temperature.bin.ctl
> define newgrid=tmpsfc-273.15
> asciigrid newgrid output.asc
>
> 4) Import into GRASS, display and compare the geographic locations of
> the temperature minima.
>
> Here are 2 links for graphics showing the apparent shift between the
> GRADS plot and the GRASS GIS plot.
>
> GRADS original:
> http://prism.oregonstate.edu/~gibson/grads/grads_original.png
> GRASS shifted: http://prism.oregonstate.edu/~gibson/grads/grass_shifted.png
>
> As you can see, the feature pointed to by the arrows in each plot has
> significantly change location in space.... about 1 degree in  
> longitude.
> I've not reset the dimensions (set x, set y)
>
> Perhaps this is an issue with the way that the National Weather  
> Service
> creates these grids.   Wesley Ebisuzaki has confirmed that the NDFD
> grids are encoded with an unusual scanning mode.  wgrib2 will not work
> with these grids and the "-new_grid" switch.
>
> At this point in time, I'm not sure what other options I have.  I've
> been using this paradigm for years converting NWS Stage IV radar  
> data in
> GRIB1 format to ASCII grids successfully ... no apparent shift in the
> data.  I tried exporting the data using fprintf but had other problems
> (sent a message to the user list a couple days ago).  Somehow I need  
> to
> export the data to an ASCII grid format.
>
> Wayne Gibson
> Oregon State University
>
> -------------------
> ga-> q config
> Config: v2.0.a8.oga.1 little-endian readline printim grib2 netcdf
> hdf4-sds hdf5 opendap-grids,stn athena geotiff shapefile
> Grid Analysis and Display System (GrADS) Version 2.0.a8.oga.1
> Copyright (c) 1988-2010 by Brian Doty and the
> Institute for Global Environment and Society (IGES)
> This program is distributed WITHOUT ANY WARRANTY
> See file COPYRIGHT for more information.
>
> Built Mon Jul 12 21:25:55 EDT 2010 for i686-pc-linux-gnu
>
> This version of GrADS has been configured with the following options:
>   o Built on a LITTLE ENDIAN machine
>   o Athena Widget GUI ENABLED
>   o Command line editing ENABLED
>       http://tiswww.case.edu/php/chet/readline/rltop.html
>   o printim command for image output ENABLED
>       http://www.zlib.net
>       http://www.libpng.org/pub/png/libpng.html
>       http://www.libgd.org/Main_Page
>   o GRIB2 interface ENABLED
>       http://www.ijg.org
>       http://www.ece.uvic.ca/~mdadams/jasper
>       http://www.nco.ncep.noaa.gov/pmb/codes/GRIB2
>       g2clib-1.1.8
>   o NetCDF interface ENABLED
>       http://www.unidata.ucar.edu/software/netcdf
>       netcdf 4.1.1 of Jul 12 2010 21:21:40 $
>   o OPeNDAP gridded data interface ENABLED
>   o OPeNDAP station data interface ENABLED
>       http://iges.org/grads/gadoc/supplibs.html
>       libgadap 2.0.oga.1
>   o HDF4 and HDF5 interfaces ENABLED
>       http://hdfgroup.org
>       HDF 4.2r5
>       HDF5 1.8.4
>   o GeoTIFF and KML output ENABLED
>       http://www.libtiff.org
>       http://geotiff.osgeo.org
>   o Shapefile interface ENABLED
>       http://shapelib.maptools.org
>
> For additional information please consult http://iges.org/grads
> --------------------------
>
>
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--
Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org



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