SWE Common Data Model OGC 08-094r1
instance so that it can be used as a key to uniquely identify andor index each one of the record components.
Requirement
http:www.opengis.netspecSWE2.0requml-record-componentsrecord-field-name-unique
Req 39. Each “field” attribute in a given instance of the “DataRecord” class shall be
identified by a name that is unique to this instance.
Example
A “DataRecord” can group related values such as “temperature”, “pressure” and “wind speed” into a structure called “weather measurements”. This feature is often used to organize the data and present it in a clear way to the
user. Similarly a “DataRecord” can be used to group values of several spectral bands in multi-spectral sensor data.
However, using a “DataArray” may be easier to describe hyper spectral datasets with several hundreds of bands.
Note: The slightly different definition of record found in ISO 19103 provides for its schema to be specified in an associated “RecordType”. When used as a descriptor, the
“DataRecord” implements the ISO 19103 “RecordType”. When used as a data container, it is self-describing: the descriptive information is then interleaved with the
record values.
7.3.2 Vector Class
The “Vector” class is used to express multi-dimensional quantities with respect to a well defined referenced frame usually a spatial or spatio-temporal reference frame. This is
done by projecting the quantity on one or several axes that define the reference frame and assigning a value to each of the axis projections.
The “Vector” class is a special case of a record that takes a collection of coordinates that are restricted to a numerical representation. Coordinates of a “Vector” can thus only be of
type “Quantity”, “Count” or “Time”. Its UML diagram is shown below:
AbstractDataComponent «Type»
Vector
«property» + referenceFrame:
SC_CRS + localFrame: SC_CRS [0..1]
+ coordinate: AnyNumerical [1..]
Figure 7.26 – Vector Class
Copyright © 2011 Open Geospatial Consortium
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OGC 08-094r1 SWE Common Data Model
Requirement
http:www.opengis.netspecSWE2.0requml-record-componentsvector-coord-name-unique
Req 40. Each “coordinate” attribute in a given instance of the “Vector” class shall be
identified by a name that is unique to this instance.
This class contains a mandatory “referenceFrame” attribute that identifies the frame of reference with respect to which the vector quantity is expressed. The coordinates of the
vector correspond to values projected on the axes of this frame.
The “referenceFrame” attribute is inherited by all components of the “Vector”, so that it shall not be redefined for each coordinate. However the “axisID” attribute shall be
specified for each coordinate, in order to unambiguously indicate what axis of the reference frame it corresponds to.
Requirement
http:www.opengis.netspecSWE2.0requml-record-componentsvector-component-no-ref-frame
Req 41. The “referenceFrame” attribute shall be ommited from all data components
used to define coordinates of a “Vector” instance.
Requirement
http:www.opengis.netspecSWE2.0requml-record-componentsvector-component-axis-defined
Req 42. The “axisID” attribute shall be specified on all data components used as
children of a “Vector” instance.
The optional “localFrame” attribute allows identifying the frame of interest, that is to say the frame we are positioning with the coordinate values associated to this component by
opposition to the “referenceFrame” that specifies the frame with respect to which the values of the coordinates are expressed.
Requirement
http:www.opengis.netspecSWE2.0requml-record-componentsvector-local-frame-valid
Req 43. The “localFrame” attribute of an instance of the “Vector” class shall have a
different value than the “referenceFrame” attribute.
Correctly identifying the local and reference frame is an important feature that allows chaining several relative positions, something that is essential to correctly compute
accurate position of sensor data especially remote sensing data.
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Copyright © 2011 Open Geospatial Consortium
