Service Interoperability Tests

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GMU WCS Server - DataFed Client Test

Accessing a test file from the GMU WCS server was completed successfully without a hitch. This possibility of actually seeing the service at work and playing with the paramters was immensily useful for this service chaining experiment. Overall it allows us to see both the progress we have in exposing satellite data through WCS as well as the remaining issues of service interoperability.

The WCS getCoverage for this test file was given by Peisheng Zhao of GMU as:

http://laits.gmu.edu/cgi-bin/NWGISS/WCS1020?
request=getCoverage&service=WCS&
version=1.0.20&
COVERAGE=%2Fdata4%2Figodata%2FMOD021KM.A2001038.1615.002.2001047054313.hdf%3ASwath%3AMODIS_SWATH_Type_L1B%3AEV_1KM_RefSB&
CRS=EPSG:4326&
RESPONSE_CRS=EPSG:4326&
BBOX=-92.323402,21.9771,-62.770599,43.1637&
FORMAT=HDF-EOS&
WIDTH=500&HEIGHT=500&
store=true

As requested, the WCS query returned a pointer to an HDF-EOS file. The images below are renderings of the various test queries using the IDL-based ENVI data visuaisation/processing softare.


Spatial Subsetting by BBOX Works Fine

This facility worked as expected. The two images below show that the data are properly set in the requested BBOX, filling the empty space with NULLS


LAITS MODIS Subset -85 25 -65 40.png LAITS MODIS Subset -125 15 -65 52.png


Subsampling Grid-Resolution Change Works Fine

The WCS query allows requesting a user-specified grid resolution of the returned data. The WIDTH=500 HEIGHT=500 parameters define the frid size. The two images below show two grid resolutions for 500 and 2000 pixels respectively. Clearly, the subsampling algorithm is working fine.

LAITS MODIS W500 H500.png LAITS MODIS W2000 H2000.png

WCS Query Questions

  • The WCS getCoverage request returns only one MODIS granule. Hence:
The user needs to know the precise file name of the granule. Question: How do I get that name.
Since each MODIS granule is a different coverage, the
Getting a coverage for multi-granule requires mosaic services using the necessary granules
sepa    the user does not have is  qu
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