Spatial Analysis II: Distance Measures and Buffers

Note: This laboratory covers material in chapters 8 and 9. It requires the ArcView Spatial Analyst extension. If you do not have Spatial Analyst, skip this lab.

Spatial Decision Support Systems (SDSS).Humans frequently need to consider a variety of factors and information in making spatial decisions. If a county needs to add a new fire station for example, the county planners will require information about suitable locations, relative costs, and potential benefits. While a software system can be designed to support optimal single-site solutions, planners have found that they prefer to be presented with several viable solutions rather than a single optimal solution. This is because there are sometimes intangible reasons for not wishing to employ the single "best" solution. Planners then want to have alternative choices that, while not the best, are still quite good. SDSS are GIS systems that serve data to a heuristic algorithm that produces multiple near-optimal solutions. In this lab, you will be using Spatial Analyst and buffers to produce a number of alternative solutions to a simulated GIS problem.

Buffer analysis, and point-in-polygon overlay. The buffer is a frequently used analysis device. Buffers calculate distances from spatial objects, and produce polygons that reflect the object and the area around it. Buffer zones are frequently used to mitigate environmental hazards. Emergency plans for nuclear power plants, for example, include multiple buffers which describe the level of hazard at increasing distance from the plant.

The overlay operation is one of the generic operations central to GIS. All types of spatial objects can be overlain in order to analyze spatial relationships between sets of objects. In this lab we will perform a point in polygon overlay analysis which will find all of the points from one data set that spatially coincide with the buffer polygons that you will create.

Spatial analysis project design. The success or failure of a GIS project generally lies in the quality of the design. There are frequently several adequate solutions to a problem using GIS, and so selecting an approach usually will devolve to considering costs such as time expended on the project. The concept of parsimony or simplicity is also a good test for the quality of a project design. In this lab, the analytic approach has been designed for you, but it is still worthwhile for you to consider whether or not this is the way you would have designed the project.