Step 1: |
Download landuse data from
http://gisdata.usgs.net/website/MRLC/viewer.php.
Either of the 1992 or the 2001 data sets may be used, though the correct code for converting the urban categories
to the categories used by the UCM should be run in step 3, below.
After selecting an area to download, make sure to select GeoTIFF format
in the "Request Summary Page" by clicking on "Modify Data Request". Previously, the data were available in BIL
format, which removed the need for format conversions in step 2; however, BIL format appears to no longer work.
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Step 2: |
After downloading the data, unpacking the archive should yield a
directory with a .tif file and a .tfw file, among others. In order for the information in the GeoTIFF
file to be useful, the .tif image must be converted into the binary format used by the WPS.
This conversion can be accomplished using the GDAL translation tool, gdal_translate,
(http://gdal.org;
pre-compiled on the classroom machines as /wrfhelp/SOURCE_CODE/gdal-1.8.1/apps/gdal_translate) by running the command
> gdal_translate -of ENVI foo.tif data.bil
where foo.tif is the name of the GeoTIFF image that was downloaded in Step 1. The output format "ENVI" is a simple
binary raster format that matches the format used by geogrid. After converting the GeoTIFF to a binary file,
the resulting data.bil file must be renamed to 00001-ncols.00001-nrows,
where ncols is the number of columns (in i5.5 format) and nrows is the number of rows (also in i5.5 format) in the
image; these values should have been printed to the screen when the gdal_translate program was run.
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Step 3: |
Re-map the categories onto categories that are defined in LANDUSE.TBL. If only urban categories are required (for use,
perhaps, with the UCM in WRF), this may be accomplished using the code for 1992 data
or the code for 2001 data (pre-compiled on the classroom machines as
/wrfhelp/SOURCE_CODE/getcat-2001). In general, either of these codes may be modified to re-map the categories
as necessary.
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Step 4: |
Create an "index" metadata file for the data.
In the directory created by unpacking the land use data, a .tfw file should also exist.
The last two lines in this file give the location of the north-west corner of the data tile, which is used
in the index file for variables known_lat and known_lon. If this location is given as
(x,y) coordinates, in meters, then the this code (available on the classroom machines
as /wrfhelp/SOURCE_CODE/convert_albers) may be used to convert to (latitude, longitude), which is required by the index file.
type=categorical
category_min=31
category_max=33
projection=albers_nad83
dx=30.0
dy=30.0
known_x=1.0
known_y=4161.0 # <- edit
known_lon=-77.673554 # <- edit
known_lat=39.582862 # <- edit
truelat1=29.5
truelat2=45.5
stdlon=-96.0
wordsize=1
missing_value=0.
row_order=top_bottom
tile_x=5449 # <- edit
tile_y=4161 # <- edit
tile_z=1
units="category"
description="3-category NLCD 2001 urban"
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Step 5: |
Add an entry to GEOGRID.TBL file specifying the path to the directory
with the data tile and index file. This entry might look something like:
===============================
name=LANDUSEF
priority=2
dest_type=categorical
interp_option = default:nearest_neighbor
abs_path = default:/mmmtmp/duda/49019336/ # The path to your new land use data
===============================
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Step 1: |
Download topography data from http://seamless.usgs.gov/
After selecting an area to download, make sure to select BIL format
in the "Request Summary Page" by clicking on "Modify Data Request".
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Step 2: |
After downloading the data, unpacking the archive should yield a
directory with a .bil file and a .hdr file. The .hdr file will give the
number of rows and columns in the data tile; using these dimensions, the
.bil file should be renamed to 00001-ncols.00001-nrows, where ncols is the
number of columns (in i5.5 format) and nrows is the number of rows (also
in i5.5 format). Since ncols and nrows can have at most 5 digits, the
data tile cannot have a dimension larger than 99999.
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Step 3: |
Create an "index" metadata file for the data.
Also in the directory, a .blw file should exist. This file gives the
(i,j) location of the upper-left corner of the data tile. Convert these
coordinates to a latitude and longitude (if they aren't already given as such)
and use them in the index file.
type=continuous
projection=regular_ll
missing_value=0.
dx=0.0002777
dy=0.0002777
known_x=1.0
known_y=3820.0 # <- edit
known_lon=-79.358497 # <- edit
known_lat=40.256750 # <- edit
wordsize=2
row_order=top_bottom
endian=little
signed=yes
tile_x=4632 # <- edit
tile_y=3820 # <- edit
tile_z=1
units="meters"
description="topography"
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Step 4: |
Add an entry to GEOGRID.TBL file specifying the path to the directory
with the data tile and index file.
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