SQUAD: A Tool for Spatial Quality and Anomalies Diagnosis – Documentation and Tutorial (QGIS version)

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Author(s): Spencer J, Wilkes B

Year: 2018

SQUAD: A Tool for Spatial Quality and Anomalies Diagnosis – Documentation and Tutorial (QGIS version) Abstract:

When working with datasets, ensuring the quality of data is always a challenge. The challenge increases with large datasets that contain hundreds or thousands of geographic coordinates. Validating spatial data can quickly become overwhelming since it is necessary to check the accuracy of both the spatial information (the accuracy and precision of the recorded coordinates) and the attribute information (data associated with that location, such as a location name, address, or associated administrative unit). Both of these domains must be accurate, and they must be in agreement.

When working with large spatial data sets, manually reviewing each record to validate both location and attribute information can be prohibitively time-consuming. A more effective approach would be to look for anomalies in the data that may indicate data quality issues. MEASURE Evaluation’s Spatial Quality Anomalies Diagnosis (SQUAD) Tool can rapidly identify the presence of any of these anomalies, which can then be investigated further to determine if there is a data quality issue. Narrowing the focus to records most likely to have an error will greatly reduce the time and effort necessary to identify and resolve errors in a database. This tool may not identify every record that has incorrect information, but it will systematically identify records that should be investigated further to resolve anomalies.

The tool produces a list of which records need to be corrected, and it also gives specific feedback on what may be wrong with the data. If these errors are identified early on, the dataset can be corrected and made stronger, more useful, and more trusted.

This tool is available as a plug-in from the QGIS website. The method for doing this is detailed in the main documentation and also in the QGIS Tool Quick Start Guide, which includes a tutorial that uses the sample data file also available below. You will need to extract the contents of this file, which should be used with the documentation and tutorial above or with the Quick Start Guide below. 

NOTE: This tool requires the use of QGIS 2.18 or 3.0. QGIS is available as a free download from www.qgis.org.

Access main SQUAD tool information page

Filed under: GIS , Data Quality , Geographic Information Systems , Spatial data