Terra Communis (tComm): a free data provider for historical census micro-data

Abstract

The growing availability of census micro-data - demographic data aggregated for small-areas, allows detailed analysis of the social structure of small neighbourhoods. Such exercises are in most cases static since census tracts geometries change between every census exercise. Using dasymmetric mapping techniques implemented within a spatially enabled PostgreSQL database, historical datasets were built for Portuguese census information, for the years 2001 and 2011. Information is freely made available using the Open Geospatial Consortium (OGC) Web Feature Service (WFS) Interface Standard. Geoserver is used to share data over the web and an interface is implemented using the JavaScript library OpenLayers. The innovative nature of tComm is three-folded: (1) for the first time, a large scale comprehensive time-space database is built for Portuguese census data; (2) the fact that data is made available online contributes to the goal of making knowledge symmetrically available; (3) the fact the only Free and Open Source Software (FOSS) is used means that, other than man-hours, the project is costs'free