Limitations of the Study

It is important to understand the limitations of GIS-based scoring systems. In order to understand how to use this point system appropriately, it is necessary to examine its limitations.

Data Driven Process

Prioritizing land for acquisition with GIS is a data-driven process. The analysis was conducted using only existing data, and data that could be derived quickly from the parcel coverage such as existing openspace and zoning. These data do not necessarily account for all of the resources that should be considered when evaluating a parcel's value as openspace.

Further discussion of data driven processes and a general critique of GIS is available in Mapping a Sense of Place another thesis at the Center for Environmental Studies by Nathan James.

A list of the data sets used in this analysis, along with a brief description of each data set is located in the metadata section of this site. The analysis conducted in this study should be used to identify possible areas for protection and to provide overview information about the site. This analysis should not be used to replace a complete site analysis when a parcel is being considered for protection. The evaluation of each individual parcel should incorporate additional data that was not available for this study

For example, there may be rare species habitat on a potential parcel that is not included in the GIS analysis but is discovered through other data sources. This information should be taken into account when the evaluating the value of the parcel for acquisition.

Accuracy of Existing Data

The accuracy of the data is another important aspect to take into account. Some of the data sets used, such as the wetlands data set, do a very good job in denoting where wetlands do or do not exist. Others, such as the cultural data sets, and the rare species habitat data sets, do not do a very good job in reflecting the spatial distribution of these resources.

A listing of these data, along with links to detailed information about their accuracy, is in the metadata section.

Rigid Process

There are many variables that must be taken into account in openspace acquisition that cannot be reflected in a GIS format. An extensive study that incorporates qualitative data into GIS has been conducted by Nathan James. The point system that was developed in this study is rigid, and does not leave room for the case by case decisions that will have to be made when acquisition occurs. An example of this might be a site's proximity to certain kinds of development, or a specific landuse that impacts the value of the land around it as openspace. Such variables could not be taken into account in this point system, so some room must be left for case by case decisions about the value of the land.