Coverages FAQ

Frequently asked questions on coverages and coverage services. -- PeterBaumann - 30 Jun 2014

How to represent a 0-dimensional coverage?

Related issues: What happens when all the CRS dimensions get sliced in a WCS request? How to encode the CIS/GMLCOV description?

Answer: As per CIS/GMLCOV, the domain set of a coverage cannot have 0 dimensionality: at least for the GML encoding, the //gml:domainSet/@dimension attribute shall be greater or equal than 1. There is no clear guidance on 0-D in the OGC standards, The recommended solution is to represent such a coverage by the single (atomic or composite) range value in the range set and an empty domain set .

Example: See the rasdaman WCS test oracle for 0-dimensional output rectified grids: browser:systemtest/testcases_services/test_wcs/oracle/18-get_coverage_0D.oracle.

Are time intervals closed or open?

Answer: Discussion on the TC Discussion list has confirmed that time intervals represent left-closed, right-open intervals, often written as [a:b). This maintains clean interval arithmetics, such as avoiding duplicate values when combining two adjacent intervals.

Related: In its latest release, ISO 8601 seems to drop 24:00 as a valid timestamp as it is equivalent to 00:00 of the next day. This removes an ambiguity where two different notations indicated the same time.
Topic revision: r2 - 27 Sep 2018, PeterBaumann
 

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