Formal description of a coverage

202 Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. urn:x-ogc:specification:gml:schema-xsd:coverage:3.2.1 All schema documents are listed in Annex C.

19.1.4 Relationship with ISO 19123

The coverage components of the GML schema specified in this clause provide a conformant, partial implementation of the ISO 19123 coverage schema. The relationship is discussed in detail in D.2.11. The ISO 19123 coverage types implemented in GML are specified in ISO 19123; additional constraints specified in ISO 19123 for these types are also constraints on the coverage components of the GML schema.

19.2 Grids schema

19.2.1 Overview

An implicit description of geometry is one in which the items of the geometry do not explicitly appear in the encoding. Instead, a compact notation records a set of parameters, and a set of objects may be generated using a rule with these parameters. This clause provides grid geometries that are used in the description of gridded coverages and other applications. In GML two grid structures are defined, namely gml:Grid and gml:RectifiedGrid.

19.2.2 Grid

gml:Grid implements ISO 19123 CV_Grid see D.2.11 and ISO 19123:2005, 8.3 and is defined as follows: element name=Grid type=gml:GridType substitutionGroup=gml:AbstractImplicitGeometry element name=AbstractImplicitGeometry type=gml:AbstractGeometryType abstract=true substitutionGroup=gml:AbstractGeometry complexType name=GridType complexContent extension base=gml:AbstractGeometryType sequence element name=limits type=gml:GridLimitsType choice element name=axisLabels type=gml:NCNameList element name=axisName type=string maxOccurs=unbounded choice sequence attribute name=dimension type=positiveInteger use=required extension complexContent complexType The gml:Grid implicitly defines an unrectified grid, which 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 region of interest within the grid is given in terms of its gml:limits, being the grid coordinates of diagonally opposed corners of a rectangular region. gml:axisLabels is provided with a list of labels of the axes of the grid gml:axisName has been deprecated. gml:dimension specifies the dimension of the grid. In GML the gml:limits element contains a single gml:GridEnvelope, in accordance with the following schema definitions: