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Running ROI_PAC on a Sandbox Wiki

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Fabrice Brito edited this page Mar 6, 2014 · 10 revisions

Understanding the processing steps

The application is described in the Application Descriptor file.

It describes two processing nodes in the Directed Acyclic Graph (DAG):

  • processing step dem
  • processing step roipac

Processing step dem

This processing step relies on an external WPS service to generate DEMs using STRM v4.1 data for ROI_PAC or GAMMA. An instance of that appliance has to be triggered to process this step.

Pseudo-code
  • invoke the DEM generation appliance OGC WPS service with one of the ASAR product reference
  • parse the DEM generation appliance OGC WPS result to grep the URL to the DEM
  • publish the downloaded DEM to the sandbox HDFS filesystem
  • pass the ASAR dataset and DEM references to the roi_pac processing step
Inputs

The processing step dem takes the Envisat ASAR pair references:

To access these URLs, you'll need to access Terradue's VPN

These products are also available on the European Space Agency (ESA) virtual archive for the Geohazard Supersites and Natural Laboratories available at http://eo-virtual-archive4.esa.int/:

The query on ESA Virtual Archive to return the pair above is: http://eo-virtual-archive4.esa.int/search/ASA_IM__0P/html?startIndex=0&start=2010-03-28&stop=2010-05-02&bbox=-116,30,-112,33&track=084

It defines:

  • a bounding box covering -116,30,-112,33 (min lon, min lat, max lon, max lat)
  • the start/end time of the Time of Interest spanning from 2010-03-28 to 2010-05-02
  • the track 084 (relative orbit in the Envisat cycle)

More information about the Virtual Archive API available here: http://eo-virtual-archive4.esa.int/help.html

|On ESA's Virtual Archive 4, browsing for data does not require being registered while downloading the data requires an ESA UM-SSO account (a few steps starting here http://eosupport.eo.esa.int/sso/registration.php)

Parameters

The processing step dem uses the DEM generation appliance OGC WPS service to generate a DEM spanning 1 degree in all directions from the first ASAR product centroid of the pair (ASA_IM__0CNPDE20100502_175016_000000172089_00084_42723_0354.N1).

The processing step dem needs the DEM generation appliance OGC WPS service access point:

http://DEM_generation_appliance_IP>:8080/wps/WebProcessingService

Output

The processing step dem produces references to

Processing step roi_pac

Pseudo-code
  • retrieve the DEM from the HDFS filesystem
  • for each Envisat ASAR products pair
  • get the acquisition date from the product metadata to create the folder YYMMDD
  • get the product identifier from the metadata to create the ROI_PAC make_raw_envi.pl invocation
  • copy the Envisat ASAR product to the YYMMDD folder
  • invoke ROI_PAC make_raw_envi.pl
  • generate the ROI_PAC proc file
  • invoke ROI_PAC process_2pass.pl
  • publish the results
Inputs

Outputs of the processing step dem

Parameters

None

Output

Outputs of ROI_PAC process_2pass.pl

Future work

Auxiliary and orbital data

The auxiliary and orbital data are contained in the repository. This is not practical for processing time-series of interferograms. To overcome this, the roi_pac step could be enhanced to pick-up the auxiliary and orbital data needed for each pair of ASAR data from a virtual archive with temporal queries:

  • get the ASAR product start and stop times
  • query the catalogue for all needed auxiliary data using the times above as time of interest
  • download the auxiliary data locally
  • repeat the approach for the orbital data
More improvements

This application produces one interferogram for a pair of Envisat ASAR data. Another application could take a stack of a master and several slaves and process in parallel the all master/slave combinations

Exploitation

This application can be exploited as an OGC Web Processing Service and scale-up on Cloud computing resources to produce interferograms that can be used as input in other toolboxes such as STAMPS or GIAnT.

References

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