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8.3.4 SquareMatrix

A SquareMatrix is a special case of an ArrayType that is considered to be two- dimensional with an equal number of elements in both dimensions. SquareMatrix is derived from AbstractMatrix and thus provides for optional localFrame and referenceFrame properties. If the coordinate frame definitions are present, the SquareMatrix coordinate values specify the transformational relationship of the localFrame to the referenceFrame. For a SquareMatrix, the required elementCount must equal the total number of elements in the matrix. Example: a 3x3 square matrix would have an elementCount of 9. The elementType for a SquareMatrix must be of type Quantity. The values can be encoded according to the encoding property. Note: A SquareMatrix is typically be used to define a transformation matrix.

8.4 Temporal Aggregates

8.4.1 Scope

ISO 19108 provides a basic temporal schema. However, there are several gaps in the schema which may be relevant in SWE. These particularly concern temporal aggregates, which occur as the independent axis of a time series. ISO 19108 provides TM_TopologicComplex but the matching temporal geometric complex is missing. Furthermore, there is no class for temporal aggregates, to parallel GM_Aggregate provided in ISO 19107 Spatial Schema. ISO 19123 provides the CV_Grid class that may be used to describe a grid in a temporal frame using time positions expressed numerically in a temporal coordinate system e.g. GPS time. We propose that a model for grids based on the conventional temporal encodings is also required. The model shown in Fig. 8.6 extends the ISO 19108 temporal schema to provide the required classes. Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 47 S e n s o r M o d e l L a n g u a g e O G C 0 7 - 0 0 0 Figure 8.6. Temporal Aggregates, geometric complex, and grid NOTE: these classes provide functionality which is also supported by the DataArray class described above, when populated with Time elements as array elements. The schema described in this sub-clause is intended to provide a model that is consistent with the idioms of ISO 19108 and ISO 19123.

8.4.2 TM_Aggregate

A TM_Aggregate is composed of member with TM_Object instances as values.

8.4.3 TM_GeometricComplex

A TM_GeometricComplex is composed of primitive TM_GeometricPrimitive TM_Instant, TM_Period instances. 8.4.4 TM_Grid, TM_InstantGrid, TM_IntervalGrid The model for a temporal grid is modelled on ISO 19123 CV_Grid. A TM_Grid is described primarily by its extent, which is a pair of integers corresponding to the low and high index of the grid in the 1-D case, and the offsetDuration giving the grid spacing. The total temporal duration covered by the grid may also be recorded. The grid is tied to an external frame by its origin which gives the position of the grid point whose index=0. Two concrete specializations are provided. TM_InstantGrid is the array of time instants corresponding to the grid points. TM_IntervalGrid is a regular array of time intervals. The duration of each interval is described by the value of the windowDuration. If the value of windowDuration is equal to the offsetDuration, then the grid intervals cover the sample space exactly. Copyright © 2007 Open Geospatial Consortium, Inc. All Rights Reserved. 48 S e n s o r M o d e l L a n g u a g e O G C 0 7 - 0 0 0

8.5 Encoding