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|Definitionskos:definition||This engineering report capture the work to extend the existing Web Coverage Service (WCS) profiles, particularly the Earth Observation Application Profile (EO-WCS [OGC 10-140r1]) to support multi-dimensional subsetting of 3D space and 1D time. The updated EO-WCS (EO-WCS1.1 [OGC 10-140r2]) have removed the requirement for the 2D coverages so that it can explicitly allow coverages with more dimensions as long as they have geographic footprint. Furthermore it also clarified the use of rangeType when non-NCNAME characters are present in a band identifier. The example of GetCapabilites, DescribeEOCoverageSet, and _GetCoverage request in the updated EO-WCS1.1 is shown with use case on fire emission data in San Francisco.Following the recommendation for EO-WCS to fully embrace the N-D, multi-dimensional, concept of Coverages as a function of time and other coordinates alongside the geospatial ones, the proposed recommendations/changes in the extension for WCS DescribeCoverage, EO-WCS DescribeEOCoverageSet, and WCS GetCoverage are discussed with use case example using National Centers for Environmental Prediction (NCEP) Global 0.25 deg wind data. Based on the mutual recommendation from the US National Aeronautics and Space Administration (NASA) and Baart et. al (2012), Network Common Data Form (NetCDF) was the output format due to presence of its libraries in multiple languages to lower the burden in changing on developers of WCS-compliant servers and clients.For the extension of the WCS DescribeCoverage, it is recommended that CIS1.1 should be considered adopting a scheme for transmitting coordinates similar to the _cis:rangeSet where data are referred to as an attached Multipurpose Internet Mail Extensions (MIME) part. Time, as much as possible, be treated as just another coordinates dimension so that it could be access with the same tools used for other coordinate dimensions. To tackle the issue on order of coordinate dimensions, it is recommended to add implementation note to the EO-WCS specifications so that implementers are aware of the mismatches between dataset coordinate reference systems (CRSs) and actual axis order.For the extension of EO_WCS DescribeEOCoverageSet, the issue on missing range of results API needed to be resolved by adding a request mechanism for requesting a range of matching results. It is also recommended that DescribeEOCoverageSet activity might be of more use to the client if the client need to supply only the subset conditions, and not a list of identifiers.For the extension of WCS GetCoverage, it was discovered that for the GetCoverage operation for higher dimensioned datasets, existing WCS-2.0 request interface provided adequate syntax for subsetting higher dimensional data. Scaling (re-gridding) operation appears to be a natural fit for the EO-WCS subsetting, specifically SCALEEXTENT activity, however simpler explanation might be needed to fully understand its use as it appears other scaling and subsetting commands may be more than adequate for the desired outcomes. Additionally allowing SlicePoint subsetting is also recommended.After performing the testing in the client side, there were few potential recommendations for improvements. More information on whether the coverage is 2D or 3D form the GetCapalilites request might be helpful to client so it can limit the number of DescribeCoverage requests to construct a list of available coverage on the server. Furthermore additional metadata information for displaying meaningful native gird coordinates is also recommended for clarification. Finally automatic detection of lat/lon axes along with clear treatment of XY and lat/lon axes ordering would be an improvement in the existing operations.|
|Creatorcreator||Ranjay Shrestha, Liping Di, Eugene G. Yu|
|OGC document typedoctype||Public Engineering Report|