Copyright © 2006. Open Geospatial Consortium, Inc. All Rights Reserved.
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6.7 Coordinate reference systems
Coverage geometries and the geometric properties of GML features and annotations include coordinates which are interpreted within the context of a coordinate reference system CRS.
According to the rules of GML, the coordinate reference system is specified via URI. This URI may identify the CRS by reference to an authority and an authority maintained code.
Alternatively, these URI may identify the physical location of a CRS definition.
In those cases where an actual CRS definition is required, GML provides a grammar for encoding such coordinate reference systems. The coordinate reference system definitions
encoded in GML can then be packaged with the JPEG 2000 data as for features etc. and referenced from the coverage description, or features, or can exist externally. This enables
both network-centric and standalone implementations of GML in JPEG 2000 to be deployed.
Some coordinate reference systems may require use of a GML coordinate reference system application schema. Mechanisms for referencing andor transporting GML application
schemas are discussed in Clause 8.
6.8 Units of
measure
Coverage values and properties of GML features and annotations may employ references to units of measure UOM. According to the rules of GML, the units are specified via URI. This
URI may identify the UOM by reference to an authority and an authority maintained code. Alternatively, these URI may identify the physical location of a UOM definition.
In those cases where an actual UOM definition is required, GML provides a grammar for the encoding of such units of measure. The units of measure definitions encoded in GML can then
be packaged with the JPEG 2000 data as for features etc. and referenced from the coverage description, or features, or can exist externally. This enables both network-centric and
standalone implementations of GML in JPEG 2000 to be deployed.
Some units of measure may require use of a GML units of measure application schema. Mechanisms for referencing andor transporting GML application schemas are discussed in
Clause 8.
7 Encoding rules for GML in JPEG 2000
7.1 Introduction
This section describes specific rules that SHALL be followed when encoding GML data for use within JPEG 2000 files.
All GML instance data associated with a specific codestream is contained in a single GML feature collection called the codestream specific feature collection, which contains the
following:
a GML Coverage objects ONE only.
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