CoverageMappingRule GridFunction, GridFunctionType Coverage schema

Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 213 element name=sequenceRule type=gml:SequenceRuleType minOccurs=0 element name=startPoint type=gml:integerList minOccurs=0 sequence complexType The gml:startPoint is the index position of a point in the grid that is mapped to the first point in the range set this is also the index position of the first grid post. If the gml:startPoint property is omitted the gml:startPoint is assumed to be equal to the value of gml:low in the gml:Grid geometry. Subsequent points in the mapping are determined by the value of the gml:sequenceRule.

19.3.14 sequenceRule, SequenceRuleType, SequenceRuleEnumeration

The sequenceRule is described by the content model: complexType name=SequenceRuleType simpleContent extension base=gml:SequenceRuleEnumeration attribute name=order type=gml:IncrementOrder attribute name=axisOrder type=gml:AxisDirectionList extension simpleContent complexType The gml:SequenceRuleType is derived from the gml:SequenceRuleEnumeration through the addition of an axisOrder attribute. The gml:SequenceRuleEnumeration is an enumerated type defined as: simpleType name=SequenceRuleEnumeration restriction base=string enumeration value=Linear enumeration value=Boustrophedonic enumeration value=Cantor-diagonal enumeration value=Spiral enumeration value=Morton enumeration value=Hilbert restriction simpleType These rule names are defined in ISO 19123. If no rule name is specified the default is “Linear”. The axisOrder attribute has the following content model: simpleType name=AxisDirectionList list itemType=gml:AxisDirection simpleType simpleType name=AxisDirection restriction base=string pattern value=[\+\-][1-9][0-9] restriction simpleType The value of a gml:AxisDirection indicates the incrementation order to be used on an axis of the grid. EXAMPLE 1 +3 means that the points in the grid are to be traversed from lowest to highest on the 3rd axis. 214 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. The different values in a gml:AxisDirectionList indicate the incrementation order to be used on all axes of the grid. Each axis shall be mentioned once and only once. EXAMPLE 2 +1 -2 +3 means that the points are to be traversed from lowest to highest on the 1st axis, starting at the highest value on the 2nd axis and the lowest value on the 3rd axis points, incremented fastest on the 1st axis before incrementing on the 2nd axis and finally the 3rd.