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The most important component of the accessibility map model is the travel time cost surface. Once created, this can be quickly used to model any number of accessibility scenarios. The ease of this process means it must be used with care and circumspection. Where it is easy to create maps, it is also easy to create maps which show any desired outcome, however unrealistic it may be. This “looking for patterns” approach can be very tempting and is often deceptive. It is far better to make decisions about location of services based on knowledge of the landscape and populations within it and then to model the results of those decisions to see their impact, rather than to play with the model with the hope that a good decision will happily drop out of it.
CIAT (2006) Accessibility Analyst http://www.ciat.cgiar.org/access/ (accessed Mar 15, 2006) The data used in this case study was taken from this CIAT website which is gratefully acknowledged.
Nelson A. & Farrow A (no date) Rural Accessibility: mapping the poverty trap Centro internacional de agricultura tropical (CIAT), A.A .6713. Cali. Colombia. On line paper
Nelson A. & Knapp E. (no date) Integrating data across geographic scales: Methods and applications in Honduras. Centro internacional de agricultura tropical (CIAT), A.A .6713. Cali. Colombia. On line paper
Nelson A. & Farrow A (2001) Accessibility modelling in ArcView 3 Centro internacional de agricultura tropical (CIAT), A.A .6713. Cali. Colombia. On line paper
The examples given in this paper were modelled in ArcGIS 9.1 Spatial Analyst which has a full cost distance mapping toolkit.