Welcome to SSAM’s documentation!

Spatial Sustainability Assessment Model (SSAM)


SSAM is a QGIS plugin for sustainability assessment in geographic environment, using environmental, economic and social criteria. It implements the algorithm TOPSIS [2] which defines a ranking based on distance from the worst point and closeness to an ideal point, for each used criteria. Entry of weights can be done directly, if known, or with the use of a pairwise comparison table; in this way the user is led to define a final vector weight, by means of a repeatable and verifiable path.

The plugin works in QGIS [3], a free and open source geographic software, widely used in several fields. With QGIS and python it is quite simple extend the software functionality and build new plugin.

SSAM is hosted in the official qgis plugin repository [http://plugins.qgis.org/plugins/] and is available under GNU GPL licence. The outputs of SSAM are both geographic and graphic. The first show the maps of the multicriteria analysis results for each elementary area. The graphic output shows the numerical value of sustainability, with the use of bars , bubbles and points .

The plugin implements the DOMLEM [4] algorithm based on the “dominance based rough set” theory [5]. With its use the user can know the decisional rules derived from the TOPSIS algorithm and have a better overview of the ranking of sustainability shown by maps and graphs. The transparency, the analysis and the back analysis capability are extremely increased.

The plugin SSAM uses a geographic vector file, eg. a shapefile, where the graphic data represent the single evaluation units (for example countries, regions or municipalities), while the alphanumeric data (the attribute table), describe the environmental, economic and social indicators. The use of the algorithms available in the plugin allow to treat separately the indicators representing the three dimensions of sustainability, and to compute three different indexes. The linear combination of the three indexes gives a overall sustainability index for each geographic unit.

The user can use a wide number of indicators (the same number of those present in the shapefile) or he can use a set of data prepared by himself. However, using the data supplied from ARPA Umbria grants more robustness and repeatability of output. In the next paragraphs we will use “plugin” and “SSAM” as synonymous. We intend for “research unit” an administrative unit described by environmental, economic and social indicators (eg. municipality, province, region, country, etc.) . The numeric output of SSAM is the “sustainability index”, given from the linear combination of three different indexes: environmental index, economic index and social index. Higher is the value of those indexes and better is the performance of a single “research unit”.