GIS modelling with rapidly changing data sets : An application of model builder to assess public accessibility in Colombo city

Abstract

Geographic Information System modelling with rapidly changing datasets requires systematic development of analysis sequences incorporating sufficient details and establishing flow of each process. Absence of a structured approach would consume a significant time for recalculations to accommodate datasets that require consistent and frequent updating.

A typical case is the modelling of the spatial variations of the accessibility in a specific land extent based on zoning changes, unwelcome incidents, national or local ceremonies etc. Apart from such dynamic data the relatively static data such as land use, road network admin boundaries become a part of a GIS model's base data set. A GIS modeller needs the vision to structure a particular application enabling the generation of output maps on each occasion of changes affected either to one, a few or all data layers. Hence it is of great importance to identify the method, strengths and weaknesses of such an application. ModelBuilder is a component of ArcGIS software which enables creating, editing and management of GIS models. There are two basic application methods. One is the capability enabling exploratory project works, and the other includes the development of generic tools that would be reused and shared. The ModelBuilder creations enable the visualization and exploration of results in ArcMap/ArcCatalogue. The ModelBuilder also facilitates the changes of parameter values, rerun selected processes, add or delete processes and intermediate data. The present work is an application of ModelBuilder to assess the spatial variability of accessibility in the city of Colombo. Data sets of 1:50,000 scales were used with ArcGIS software. The systematic development of ModelBuilder assembly and the potential of GIS modelling results generation with ease for varying data layers. Situations are demonstrated.

These types of applications enable the public to identify locations suitable for access as a result of various scenarios such as public rallies or public unrest situations which may not be predictable, or due to scenario which may periodically occur within a day such as morning and evening, evening office rush periods, or school traffic durations. Therefore, this ModelBuilder application would help resource managers to customize spatial data set based models to facilitate rapid and rational decision making.