IMPLEMENTING SPACE SYNTAX IN AN OPEN SOURCE GIS : GRASS GIS approach 100

Being a set of techniques for analyzing spatial patterns in buildings and cities, space syntax has been implemented in various software of spatial analysis. Due to the common requirement of handling spatial information, a significant portion of this spatial analysis software is built upon a geographic information system (GIS). Although these spatial analysis software may be available free of charge for academic or noncommercial use, they have to run inside a proprietary GIS such as MapInfo or ArcView, or a proprietary CAD such as AutoCAD or Microstation. The emergence of free and open source software is one of the most significant computer-related developments in recent years. The philosophy is about freedom, which means users of such a computer program have the freedom to run it, study how it works and adapt it to their needs, redistribute it, and improve it and release the improvement to the public. This philosophy is particularly attractive to academia in that knowledge embedded in such software will be preserved, disseminated, and further developed regardless the commercial viability of the software. Linux operating system and Apache HTTP server are two most well known examples of free and open source software. In terms of GIS, Geographic Resources Analysis Support System (GRASS) is the oldest and most popular full-fledged GIS released as free and open source software. With the advent of GRASS 6 and its much improved vector map processing capabilities, it became feasible to implement the space syntax techniques in an open source GIS. This paper describes an experimental implementation of the space syntax techniques in GRASS 6 that relies particularly on its vector network analysis modules and scripting capability. To test the effectiveness of the implementation, a case study is conducted using the same chosen study area but with two different street configurations, which are before and after the development of a special district for a high-speed railway station in the central part of Taiwan. The result shows that given the enormous capacities and flexibility of GRASS, the implementation is rather straightforward and works as expected. This demonstrates the true value of taking the open-source approach.