[gradsusr] Geotiffs in Grads
Yaqiang Wang
yaqiang.wang at gmail.com
Wed Dec 22 02:42:13 EST 2010
In fact, your data is tif not geotif. The tfw file is world file for
geolocation of the image, but it's not the projection parameters.
Your 'tfw' file obviously is not correct with too big x and y scales.
I ajust the x and y scales to 0.017 and the geolocated figure is
attached. It's still not correct, because I don't know the exactly the
geo-location of the image. If you know, you can adjust it to the right
location.
The description of world file is following:
World File
Images are stored as raster data, where each cell in the image has a
row and column number. In order to display images in real-world
coordinates, it is necessary to establish an image-to-world
transformation that converts the image coordinates to real-world
coordinates. This transformation information is typically stored with
the image.
This information was stored in a separate ASCII file. This file is
generally referred to as the world file, since it contains the
real-world transformation information used by the image. World files
can be created with any editor. They can also be created using
MeteoInfo.
It’s easy to identify the world file which should accompany an image
file. The first and third characters of the image file’s suffix and a
final "w" are used for the world file suffix. Therefore, for
‘mytown.tif’, the world file would be ‘mytown.tfw’. For
‘redlands.gif’, its world file would be ‘redlands.gfw’.
The contents of the world file will look something like this:
20.17541308822119 -A
0.00000000000000 -D
0.00000000000000 -B
-20.17541308822119 -E
424178.11472601280548 -C
4313415.90726399607956 -F
When this file is present, it performs the image-to-world transformation.
A = x-scale; dimension of a pixel in map units in x direction
B, D = rotation terms
C, F = translation terms; x,y map coordinates of the center of the
upper-left pixel
E = negative of y-scale; dimension of a pixel in map units in y direction
Note: The y-scale (E) is negative because the origins of an image and
a geographic coordinate system are different. The origin of an image
is located in the upper-left corner, whereas the origin of the map
coordinate system is located in the lower-left corner. Row values in
the image increase from the origin downward, while y-coordinate values
in the map increase from the origin upward.
On Wed, Dec 22, 2010 at 11:44 AM, Nick Heath <nkh09 at fsu.edu> wrote:
> Hi,
>
> Thanks for the information. I have attached the geotiff file that I used to create the ASCII grid format along with the world file that accompanied it. Thank you all again for the help.
>
> -Nick
>
> ----- Original Message -----
> From: Yaqiang Wang <yaqiang.wang at gmail.com>
> Date: Tuesday, December 21, 2010 7:37 pm
> Subject: Re: [gradsusr] Geotiffs in Grads
> To: GrADS Users Forum <gradsusr at gradsusr.org>
>
>> Hi Nick,
>>
>> I have checked your data. "20100424_160000.asc" is ESRI ASCII Grid
>> format data which could be supported in many GIS software. The problem
>> is I don't know the projection information of the data which is not
>> longitude/latitude coordinate, and the ESRI ASCII Grid format has no
>> information of the projection. The projection information should has
>> been included in the geotiff file.
>>
>> On Wed, Dec 22, 2010 at 3:54 AM, Nick Heath <nkh09 at fsu.edu> 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
>> >>
>> >>
>> >>
>> >>
>> >
>> > _______________________________________________
>> > gradsusr mailing list
>> > gradsusr at gradsusr.org
>> > http://gradsusr.org/mailman/listinfo/gradsusr
>> >
>> >
>>
>>
>>
>> --
>> *************************************************
>> Dr. Ya-Qiang Wang
>> Centre for Atmosphere Watch and Services (CAWAS), CMA
>> Chinese Academy of Meteorological Sciences (CAMS)
>> 46, Zhong-Guan-Cun South Avenue
>> Beijing, 100081
>> China
>>
>> yaqiang.wang at gmail.com
>> **************************************************
>>
>> _______________________________________________
>> gradsusr mailing list
>> gradsusr at gradsusr.org
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>>
>
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>
--
*************************************************
Dr. Ya-Qiang Wang
Centre for Atmosphere Watch and Services (CAWAS), CMA
Chinese Academy of Meteorological Sciences (CAMS)
46, Zhong-Guan-Cun South Avenue
Beijing, 100081
China
yaqiang.wang at gmail.com
**************************************************
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