Changes between Version 12 and Version 13 of PetascopeSubsets

Timestamp:

Mar 22, 2014, 12:33:23 AM (11 years ago)

Author:

Piero Campalani

Comment:

—

PetascopeSubsets

@@ -14 +14 @@
  ''What is a grid? :: As by [http://www.opengeospatial.org/standards/gml GML standard] a grid is a ''"network composed of two or more sets of curves in which the members of each set intersect the members of the other sets in an algorithmic way"''. The intersections of the curves are represented by points: a point is 0D and is defined by a single coordinate tuple (see ISO:19107 `GM_Point`).
 
-A first question arises on where to put the grid '''origin'''. The GML and [https://portal.opengeospatial.org/files/?artifact_id=48553 GMLCOV] standards say that the mapping from the domain to the range (feature space, payload, values) of a coverage is specified through a function, formally a `gml:coverageFunction`.  The default mapping which is assumed when no coverage function is described. From the GML standard: ''"If the `gml:coverageFunction` property is omitted for a gridded coverage (including rectified gridded coverages) the `gml:startPoint` is considered to be the value of the `gml:low` property in the `gml:Grid` geometry, and the `gml:sequenceRule` is assumed to be linear and the `gml:axisOrder` property is assumed to be `+1 +2`"''. 
+A first question arises on where to put the grid '''origin'''. The GML and [https://portal.opengeospatial.org/files/?artifact_id=48553 GMLCOV] standards say that the mapping from the domain to the range (feature space, payload, values) of a coverage is specified through a function, formally a `gml:coverageFunction`. From the GML standard: ''"If the `gml:coverageFunction` property is omitted for a gridded coverage (including rectified gridded coverages) the `gml:startPoint` is considered to be the value of the `gml:low` property in the `gml:Grid` geometry, and the `gml:sequenceRule` is assumed to be linear and the `gml:axisOrder` property is assumed to be `+1 +2`"''. 
 
 To better understand this, the following image is showing the difference between a ''linear'' sequence rule (what we adopt) and an other kind of mapping, the so-called ''boustrophedonic'' (check out [http://www.schemacentral.com/sc/niem20/e-gml_sequenceRule-1.html this] page for other available rules):