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Geographic Information Systems (GIS) provide a powerful way to visualize and analyze spatially distributed data. Geographic Information Systems (GIS) are a set of computer programs that can organize, display, and analyze spatially distributed data. At its simplest, GIS is "mapping", providing a geographic arrangement of diverse information, allowing for visual comparison. Such maps are therefore a powerful means to educate, in class and in publications. Additional GIS tools can extract related features, provide geostatistical analysis, and generate 3D models and movies of time-dependent changes. GIS has been applied in geology, biology, psychology, anthropology, sociology, linguistics, history, political science, economics, and many other fields. GIS data is commonly in one of two forms: Raster: A grid of rows and columns of colored cells. These might represent
photographic or scanned images. Vector: A geometric shape, including points, lines, and polygons. These might represent buildings, roads, and counties. Either of these can have tables of data associated with them, e.g. elevation, population, financial values, etc. These associated data can be used to color a map so that it conveys information with visual impact. Some samples of GIS-produced maps for the town of Amherst are shown below, clear evidence of its cross-disciplinary value. The data underlying these maps comes from many sources: the Town of Amherst, the State of Massachusetts, the U.S. Census Bureau, and the U.S. Geological Survey.
Course OverviewBecause of its diverse applications and multiple data types, learning GIS can take several classes. First Class: Constructing and Sharing MapsYou will learn to construct maps using GIS data such as the above. You will discover how to use GIS for exploratory analysis of geographic data. You will also learn how to export your maps into a number of formats such as PDF or Google Earth, so that it can be shared with others who don't have this GIS software. The data has been prepared (geographically referenced) in advance so that you can focus on the general skills required to work with it. Often geographic data is not ready-to-use, and in subsequent classes you learn how to use these different formats. Second Class: Mapping Place Name DataYou will learn to map data from tables that use names for geographic locations. This includes census data and street address data. In these simple tables, information about each geographic region is in a single row, viz. its name and attribute data. This type of data can be geographically
referenced by associating it with existing prepared data. Third Class: Mapping Coordinate DataYou will learn about geographic spatial references and how the globe is projected onto flat maps on computer screens and paper. In the process you'll learn to map another common tabular format for geographic data that uses X-Y coordinates such as latitude and longitude. The data collected by a Global Positioning System (GPS) receiver is in this format. This type of data
can be geographically referenced by associating it with descriptions
of its spatial reference (i.e. how its coordinate system is oriented
in space). Fourth Class: Mapping Raster DataYou will learn about the basic characteristics of rasters, which represent a regular grid of data covering the Earth’s surface. Examples include aerial or satellite photos, scanned maps, and digital elevation models. Their regularity and coverage allow rasters to be used in calculations to determine characteristics such as watersheds — regions of land where water flows downhill and through a particular location (usually the mouth of a stream or river). You will also learn how to georeference scanned paper
maps, which still
provide a lot of information about our world; when brought into a GIS they can be overlayed with other data for comparison. Fifth Class: Editing Map Data and GeostatisticsScanned maps usually include features that you may want to extract, e.g. houses, roads, property boundaries, etc. With ArcGIS’s vector editing tools, such features can be traced into new sets of GIS data. Editing tools also allow you to work with existing vector data to transform it in various ways, e.g. merging or splitting polygons, reshaping lines, etc. Geostatistics is the application of statistics to the characterization and modeling of geographically distributed data. It is based on the observation that locations generally have similar characteristics, implying that they are not independent of each other. As seen in the previous section, there is a wide variety of data that can be used to build your own maps. Finding this data and pulling it together in a usable format is typically the largest effort involved in GIS. For example, data from the Third World or precise historical data can be difficult to come by. As a result, the most effective academic uses of GIS are:
The Reference Librarians will be of great assistance in obtaining existing data, and Academic Technology Services can assist you in all of these activities. The ArcGIS SoftwareThe ArcGIS software that Amherst College provides has made "desktop GIS" a reality. Geographic Information Systems have been around for more than fifty years, but have become increasingly accessible as computing power has increased. Amherst College has one of the best GIS available, the Arc products from Environmental Systems Research Institute commonly referred to as ESRI. Their current software, ArcGIS, has made GIS significantly easier than it was even a decade ago. There are also a large number of extensions, for example for
spatial or three-dimensional analysis. ArcGIS is available on all Windows computers in most campus computer labs, as well as on classroom projection computers. Faculty, staff, and students can install ArcGIS on any Windows computer where they are administrators, from the Amherst Software Collection. Anyone with a Windows computer can also install the free program ArcReader (available from ESRI), allowing them to view "published maps" produced by ArcGIS. Contact Academic Technology Services for
more information or assistance. Additional GIS Training and ResourcesThere are many other options for learning GIS and extending your knowledge. Amherst College's license for the ArcGIS software includes a number of online courses prepared by ESRI. Contact Academic Technology Services for more information or to obtain a license code. Amherst College maintains a collection of ArcGIS documentation in the form of Adobe Acrobat (PDF) digital books, on the network at
including:
The K:\Maps folder also contains a great deal of data that can be used as the foundation for your own maps. The Amherst College Library maintains a web page of GIS resources, including links to the GIS books in the library's collection. There are a number of tutorials that can be found on the Internet, some of which are:
ESRI also provides a useful collection of tips and shortcuts for the Arc software.
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