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/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2011, Open Source Geospatial Foundation (OSGeo)
* (C) 2004-2005, Open Geospatial Consortium Inc.
*
* All Rights Reserved. http://www.opengis.org/legal/
*/
/**
* {@linkplain org.opengis.metadata.quality.DataQuality Data quality} and {@linkplain
* org.opengis.metadata.quality.PositionalAccuracy positional accuracy}. The following is adapted
* from OpenGIS® Spatial
* Referencing by Coordinates (Topic 2) specification.
*
* The parameters that define a coordinate reference system are chosen rather
* than measured to satisfy the degrees-of-freedom problem in the changeover from observation to
* coordinate quantities. Coordinate reference systems are therefore by definition error-free (i.e.,
* non-stochastic). A coordinate reference system is realised through a network of control points.
* The coordinates of those control points, derived from surface and/or from satellite observations,
* are stochastic. Their accuracy can be expressed in a covariance matrix, which, due to the
* degrees-of-freedom problem, will have a rank deficiency, described in geodetic literature.
*
*
Coordinate transformations between coordinate reference systems usually have
* parameter values derived from two sets of point coordinates, one set in system 1, the other set
* in system 2. As these coordinates are stochastic (i.e., have random-error characteristics) the
* derived transformation parameter values will also be stochastic. Their covariance matrix can be
* calculated.
*
*
Coordinates that have not been "naturally" determined in coordinate reference
* system 2, but have been determined in coordinate system 1 and then transformed to system 2, have
* the random error effects of the transformation superimposed on their original error
* characteristics. It may be possible in well-controlled cases to calculate the covariance matrices
* of the point coordinates before and after the transformation, and thus isolate the effect of the
* transformation, but in practice a user will only be interested in the accuracy of the final
* transformed coordinates.
*
*
Nevertheless the option is offered to specify the covariance matrix of point
* coordinates resulting exclusively from the transformation. It is outside the scope of this
* specification to describe how that covariance matrix should be used. Because a covariance matrix
* is symmetrical, only the upper or lower diagonal part (including the main diagonal) needs to be
* specified.
*
*
For some transformations, this accuracy information is compacted in some
* assessment of an average impact on horizontal position and vertical position, allowing
* specification of average absolute accuracy and, when relevant and available, average relative
* accuracy. Hence separate quality measures may be specified for horizontal and for vertical
* position in those objects.
*
* @version ISO 19115
* @since GeoAPI 2.0
*/
package org.opengis.metadata.quality;