dataQuality.xsd 3.0 How to encode positional data quality information. Builds on units.xsd to encode the data needed to describe the positional accuracy of coordinate operations. Primary editor: Arliss Whiteside. Last updated 2003/05/21. Copyright (c) 2002-2003 OpenGIS, All Rights Reserved. This schema encodes the Data Quality (DQ) package of the extended UML Model for OGC Abstract Specification Topic 2: Spatial Referencing by Coordinates. That UML model is adapted from ISO 19111 - Spatial referencing by coordinates, as described in Annex B of Topic 2. Position error estimate (or accuracy) data. A description of the position accuracy parameter(s) provided. Closeness of reported coordinate values to values accepted as or being true. Closeness of the relative positions of two or more positions to their respective relative positions accepted as or being true. Quantitative result determined by evaluation procedure used. Error estimate covariance matrix. Ordered sequence of units of measure, corresponding to the row and column index numbers of the covariance matrix, starting with row and column 1 and ending with row/column N. Each unit of measure is for the ordinate reflected in the relevant row and column of the covariance matrix. Unordered sequence of elements in this covariance matrix. Because the covariance matrix is symmetrical, only the elements in upper or lower diagonal part (including the main diagonal) of the matrix need to be specified. Any zero valued covariance elements can be omitted. An element of a covariance matrix. Row number of this covariance element value. Column number of this covariance element value. Value of covariance element.