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With beaches eroding, how much sand is being added to a system? With this sand being carried along the shore by currents, how much of this sand is being deposited in spits? A geographic information system (GIS) can be used to help answer these questions.

A GIS is computer software that can statistically analyze and map spatial data. The software can perform a wide variety of functions including calculating dimensions (length, area, etc.), determining arrangement (number of geographic features within a set distance, etc.), modeling surfaces (slope direction, slope angle, visibility, etc.), and much more. The following web sites provide examples of GIS analyses:

Local Examples:

http://camelot.coastal.edu/data.php

http://www.scgn.net

 

Other Examples:

http://www.esri.com/news/arcnews/arcnews.html

http://www.esri.com/software/internetmaps/visit_sites.html

http://www.nps.gov/yell/technical/gis/examples.html

For this project, the computer software was used to rectify scanned historical aerial photographs. The rectification process projects a photograph onto a known map, so that locations on the picture have correct geographic positions (altering the shape of the photograph so that it lines up with the map). After the rectification, pointing at a road intersection (or corner of a building, center of a tree, etc.) on the projected photograph will give a correct latitude and longitude position as would measuring that location on the map. The rectification process is accomplished by creating links between distinct features on the historical photographs with known location on a map (or an already corrected aerial photograph). Using several links, the computer them maps the photograph into the correct geographic location. Once corrected, the aerial photographs can be used to examine coastal change by map overlay, similar to flipping through paper maps of same size and area (which is not always the case with paper maps!).