[gradsusr] Geotiffs in Grads

Wed Dec 22 22:35:58 EST 2010

Yaqiang Wang and Jennifer,

Thanks you both for your help.  I have tried the script you (Jennifer) wrote for me and it is working correctly, but I too am having trouble getting the resolution right.  I will keep working on it.  This has been extremely helpful.

Thanks,
Nick

----- Original Message -----
From: Jennifer Adams <jma at cola.iges.org>
Date: Wednesday, December 22, 2010 11:24 am
Subject: Re: [gradsusr] Geotiffs in Grads
To: GrADS Users Forum <gradsusr at gradsusr.org>

> Nick,
> If you use the following script, you can convert the data in the 
> third  
> column of 20100424_160000.dat (presumably the oil/no-oil grid) into 
> a  
> binary file. Note that dummy.ctl can be any GrADS data set, it is  
> irrelevant, you just need to have some file open, and I changed the 
> 
> 'oil' value from 16777215 to 1.
> 
> 'open dummy.ctl'
> 'set gxout fwrite'
> file = "20100424_160000.dat"
> 'set fwrite c3.dat'
> row=1
> while (row<=212930)
>   ret = read(file)
>   rc = sublin(ret,1)
>   data = sublin(ret,2)
>   c1 = subwrd(data,1)
>   c2 = subwrd(data,2)
>   c3 = subwrd(data,3)
>   if (c3=16777215)
>     'd 1'
>   else
>     'd 0'
>   endif
>   row = row+1
> endwhile
> rc = close(file)
> 'disable fwrite'
> 
> After you do that, this descriptor file will load that binary grid  
> into GrADS:
> 
> dset ^c3.dat
> xdef 535 linear 1 1
> ydef 398 linear 1 1
> *xdef 535 linear -1.0515988822025 175.4381134356
> *ydef 398 linear -58.3371844811313 175.4013801622
> title c3
> undef -9.99e8
> zdef 1 levels 0
> tdef 1 linear 1jan0001 1dy
> vars 1
> c3 0 99 c3
> endvars
> 
> I left the 0's in as valid data and used -9.99e8 as a missing 
> value,  
> but you could use 0 as an undef if you wanted to. The commented out 
> 
> lines for xdef and ydef reflect the values in the first and second  
> columns of your original .dat file (by the way, it's not a good  
> practice to give a file containing ascii a .dat extension). I don't 
> 
> know what those grid values mean -- you must figure out if or how 
> they  
> map to latitude and longitude. I couldn't figure out the 
> geolocation  
> by loading your geotiff file into Quantum GIS, a tool that will  
> display a Geotiff, but it did provide this metadata: "Layer Spatial 
> 
> Reference System: +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs".
> 
> --Jennifer
> 
> 
> On Dec 21, 2010, at 2:54 PM, Nick Heath wrote:
> 
> > Hi,
> >
> > Thank you both for the help!  I have found a way to convert the  
> > geotiffs into gridded data.  I have attached 2 of the output 
> files  
> > after the conversion (I tried two different formats).  Now, I am 
> a  
> > bit lost on how to make a control file with this data as I am 
> used  
> > to working with Grib or netcdf.  Maybe someone could help?  In  
> > the .dat file, I believe the 3 columns are Y,X, and either 0 (no  
> > oil) or 16777215 for oil.  I am not sure why the converter picked 
> 
> > that number.  Thanks an advance for the help!
> >
> > -Nick
> >
> > ----- Original Message -----
> > From: Jennifer Adams <jma at cola.iges.org>
> > Date: Tuesday, December 21, 2010 10:48 am
> > Subject: Re: [gradsusr] Geotiffs in Grads
> > To: GrADS Users Forum <gradsusr at gradsusr.org>
> >
> >> Hi, Nick --
> >> What you are asking for is a 'dtype geotiff' which does not exist
> >> in
> >> GrADS. Turning the information in a geotiff file into a grid of
> >> values
> >> that you can analyze with GrADS is a job for customized stand-alone
> >>
> >> code. You may find some useful utilities to help you get started in
> >>
> >> the libgeotiff distribution.
> >> --Jennifer
> >>
> >>
> >> On Dec 21, 2010, at 10:29 AM, Nick Heath wrote:
> >>
> >>> Hi everyone,
> >>>
> >>> I am working with oil spill data, and I need a way to display the
> >>
> >>> oil in my model.  I have geotiffs of the oil locations and I was
> >>> wondering if there is any way to read those into Grads.  I also
> >> have
> >>> the locations in .gif files.  If that is not possible, does
> >> anyone
> >>> have any good ideas of how I could make a "blob" of oil that I
> >> could
> >>> apply equations to (such as a wind drift to watch how it moved
> >>> through time)?
> >>>
> >>> Here is the config of the Grads I'm using:
> >>>
> >>> Config: v2.0.a8 little-endian readline printim grib2 netcdf 
> hdf4-
> >> sds
> >>> hdf5 opendap-grids,stn geotiff shapefile
> >>> Grid Analysis and Display System (GrADS) Version 2.0.a8
> >>> 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 Fri Mar 26 10:24:10 EDT 2010 for x86_64-unknown-linux-gnu
> >>>
> >>> This version of GrADS has been configured with the following
> >> options:>  o Built on a LITTLE ENDIAN machine
> >>> o Athena Widget GUI DISABLED
> >>> 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-rc2 of Mar 23 2010 09:31:58 $
> >>> o OPeNDAP gridded data interface ENABLED
> >>> o OPeNDAP station data interface ENABLED
> >>>     http://iges.org/grads/gadoc/supplibs.html
> >>>     libgadap 2.0
> >>> o HDF4 and HDF5 interfaces ENABLED
> >>>     http://hdfgroup.org
> >>>     HDF 4.2r3
> >>>     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
> >>>
> >>> Thanks for the help!
> >>>
> >>> Nick
> >>> _______________________________________________
> >>> gradsusr mailing list
> >>> gradsusr at gradsusr.org
> >>> http://gradsusr.org/mailman/listinfo/gradsusr
> >>
> >> --
> >> Jennifer M. Adams
> >> IGES/COLA
> >> 4041 Powder Mill Road, Suite 302
> >> Calverton, MD 20705
> >> jma at cola.iges.org
> >>
> >>
> >>
> >>
> > < 
> > 20100424_160000 
> > .zip 
> > 
> ><20100424_160000.asc>_______________________________________________> gradsusr mailing list
> > gradsusr at gradsusr.org
> > http://gradsusr.org/mailman/listinfo/gradsusr
> 
> --
> Jennifer M. Adams
> IGES/COLA
> 4041 Powder Mill Road, Suite 302
> Calverton, MD 20705
> jma at cola.iges.org
> 
> 
> 
> 