by Michael Silberbauer
Poster at AGILE 2011, the 14th AGILE international conference on geographical information science
In arid regions, the effect of pollutants on the quality of water resources is much greater than under hydrological... more
In arid regions, the effect of pollutants on the quality of water resources is much greater than under hydrological regimes that have an abundance of water for dilution. Thus in dry areas, the monitoring of water chemistry is a very important component of water resource management. Spatial visualisation assists managers by pinpointing areas where anomalies in chemical composition of solutes occur. Multivariate point symbols provided by commercial and open source GIS are usually limited to pies and bar charts, which are difficult to compare visually on a map. Fortunately, the well-known Maucha ionic diagram is fairly easy to program. In southern Gauteng Province in South Africa, the characteristic sulphate spike in the lower left of certain Maucha symbols shows sites where the ionic balance has changed from the natural ratio, dominated by calcium and bicarbonate, to an abnormal, sulphate-dominated ratio. The Maucha symbol utilises the human visual system’s ability to detect angular displacement quickly and accurately and combines the ‘pop-out’ visual cues of angle, colour and size that trigger an automatic response in the visual cortex. This type of multivariate spatial analysis of point data can reveal important trends and the GIS that can provide this facility as a built-in feature will be much sought after.
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