Hi,
I’m trying to generate a GPT workflow. I don’t have a complete functioning GPT file yet, so I’m posting here and not in the GPT sub-forum. Please let me know if you’d like to see GPT questions in the sub-forum or only mature workflows.
I’m trying to reproject a Sentinel 3 scene to a specific projection, subset, and resolution. Specifically, I am trying to match this description;
Map Projection: Sinusoidal
Map Reference Latitude: 0
Map Reference Longitude: 0
Map Equatorial Radius: 6371007.181 ;wgs84 meters
Map Origin X: -3335851.559000007
Map Origin Y: 10007554.676999498
Grid Map Origin Column: -0.5
Grid Map Origin Row: -0.5
Grid Map Units per cell: 500
Grid Width: 7200
Grid Height: 7200
I’ve determined that the “Sinusoidal” refers to the MODIS global sinusoidal grid (see image here: https://nsidc.org/data/docs/daac/mod10_modis_snow/landgrid.html ) and I’m looking at Greenland which is under Tiles h15v00 through h17v02.
I can re-project to the MODIS Sinusoidal grid and downsample to 500 m resolution with a GPT element of:
<node id="Reproject">
<operator>Reproject</operator>
<sources>
<source>BandSelect</source>
</sources>
<parameters>
<crs>PROJCS["MODIS Sinusoidal",
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.01745329251994328,
AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4326"]],
PROJECTION["Sinusoidal"],
PARAMETER["false_easting",0.0],
PARAMETER["false_northing",0.0],
PARAMETER["central_meridian",0.0],
PARAMETER["semi_major",6371007.181],
PARAMETER["semi_minor",6371007.181],
UNIT["m",1.0],
AUTHORITY["SR-ORG","6974"]]</crs>
<resampling>Nearest</resampling>
<orthorectify>false</orthorectify>
<noDataValue>NaN</noDataValue>
<includeTiePointGrids>false</includeTiePointGrids>
<addDeltaBands>false</addDeltaBands>
<pixelSizeX>500.0</pixelSizeX>
<pixelSizeY>500.0</pixelSizeY>
</parameters>
</node>
What I’m now having trouble with is how to shift this to the exact offsets and trim to 7200 x 7200 pixels. Do I set -pnorthing
to Map Origin Y
? And same for easting
and X
?. And use the Reproject
operator width
and height
? Or should this be done in separate GPT operators such as Resample
and Subset
?
Thanks,
-k.