GIS Mapping

GIS Mapping

The Geographical Information System, or GIS, is a continually growing resource used to visualize and understand geographical data. The system reveals relationships and trends in a particular area through maps, reports and charts. It is used throughout the world to connect the social, economic, environmental, and physical aspects of a community in a way to allow the members of that community to “work in a much more interactive way to address the multi-faceted nature of [their] informal settlements” (Abbott, 2003). GIS mapping is a tool used in urban planning, which makes it especially beneficial to informal settlements due to their lack of infrastructure and framework and their need of redevelopment. GIS is effective because it can express the social, economic, and demographic changes that can be expected when a physical change is proposed in the area (Abbott, 2001b).

GIS maps are very versatile and can show themes, patterns, individual features, quantitative data, density data, and much more (ESRI, 2009). They use three different types of images: points, lines, and polygons. Points represent a specific location, such as an address. Lines represent features including area boundaries, roads, and contour lines. Polygons represent different areas with similar characteristics. For example, a polygon of a certain color shown on a GIS map could indicate an area of a city that has over 70% Hispanic population, while a polygon of a different color could indicate an area with over 70% Asian population. Polygons can also represent structures such as churches, businesses, and schools (WPI CTPC, 2008).

By examining a GIS map one can determine the distribution of demographic features in a particular area and therefore can predict emerging patterns (ESRI, 2009). A GIS map can also exemplify certain demographics so that a community is able to plan accordingly. For example, most urban communities plan for an emergency evacuation in case of a natural disaster or a similarly dangerous event. By using a GIS map, the community can observe locations of low income families who may have difficulty evacuating a dangerous situation for reasons like lack of personal transportation. For that reason, it would be beneficial for urban planners to develop a public transportation system or any other evacuation plan particularly in the extremely low-income neighborhoods.

Usually, a GIS map is used to illustrate data that has already been collected. However, informal settlements have limited data due to the fact that they are less frequently analyzed than “legal” settlements or communities. This creates a more challenging approach to redevelopment in these areas. Often the only available data is an aerial view of the settlement. If an aerial map is not provided, a planner must either draw a layout of the city to the best of his or her ability by hand or using a computer program, or obtain an aerial photo from a different source. If an aerial map is provided, the different points, lines, and polygons are simply drawn over the map to indicate their locations. The process of locating these different features starts with conducting several mapping exercises with the community members and co-researchers. Mapping exercises could include locating street lighting, emergency access roads, or most popular routes of travel on the aerial map, followed by taking pictures of the map with the new data drawn on it. These pictures are then documented and digitized into GIS (WPI CTPC, 2008). The data shown on a GIS map of an informal settlement is similar to that of a formal community, including demographic and socio-economic data, economic opportunities, physical planning and design data, and housing data (Abbott, 2003).

One major objective of urban upgrading in an informal settlement is to educate the residents about what their existing community looks like compared to what a sustainable community looks like, and how this sustainability is achieved. GIS mapping will allow the community to obtain a physical image of “the interaction between the spatial and physical elements on the one hand, and the social and economic opportunities on the other” (Abbott, 2003) that the changes will bring. This image creates a comprehensible technique for educating the community members. Furthermore, the maps created using GIS can be used in future redevelopment and urban planning and mapping efforts.

In our project we used two different computer programs for our mapping: Google Earth and Arc GIS. Click either name to learn more.