Enviroware s.r.l.

The Google Earth tool for studying Air Quality

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Any person involved in air quality studies knows that cartographic representation of data (input, output or measured) is very important, time consuming and, most often, difficult. One of the difficulties is to find a suitable cartographic base over which the information (sources, sensible receptors, buildings, isopleths, etc.) must be represented. Sometimes the cartographic base is available, but it is not georeferenced, therefore the user must try to reference it using the coordinates of some known points and the dimension in pixels of the image. This procedure may introduce some positioning mistakes. When things go well, there are georeferenced images (for example tiff images with their world file – or tfw files) which can be loaded in GIS systems. The drawback of the GIS systems is that their use presents some difficulties and they are expensive (with some noticeable exceptions of free systems, such as MapWindow and TatukGIS). Most often the cartographic georeferenced bases are very expensive. Since some years a new powerful tool, Google Earth (abbreviated with GE sometimes in the rest of the document), is available to (virtually) navigate over the globe, finding places and visualising information. Google Earth (http://earth.google.com/) is a computerised 3D representation of the world that uses satellite, aerial and geographic information system imagery combined with mapping software. Moreover, digital topographic data from NASA and other sources are used to model orography. The Google Earth interface allows to insert very easily graphical and textual information, but the great power of the tool is the KML language (Keyhole Markup Language ), which allows to show very complex information with a relatively simple syntax. Google Earth is a geographic browser, and the KML is its language, just as HTML is the language of the internet browsers. Other geographic browsers exist, as for example Microsoft Live Earth and NASA World Wind, but this document focuses on Google Earth. This document describes some possible uses of Google Earth for representing Air Quality (AQ) data. In particular it shows how Enviroware uses Google Earth to represent AQ data in its air dispersion evaluation studies.

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