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Geographic Information Systems

This guide will help you get started with understanding what GIS is, the nature of geospatial data used in GIS, and how to get started using GIS for your research.

What is Geospatial Data?

Geospatial data is data that contains location or geographic information. This means that the records in a dataset have locational information tied to them such as geographic data in the form of coordinates, address, city, or ZIP code. Geospatial data comes in many formats. The format type depends on data to be displayed. File formats are categorized as vector, raster, imagery, and legacy GIS file formats.They can then be layered and analyzed to visualize data.

Vector Data

Vector data is a representation using points, lines, and polygons. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and streets. Common formats include Shapefiles and File Geodatabase Feature Classes

The vector data displayed below depicts the eight districts of the New Orleans Police Department.

Raster Data

A raster consists of pixels organized into a grid. Each cell is comprised of a value representing information. Raster data is data in a .JPG, .TIF, .GIF or similar format. Items scanned using a flatbed scanner like this map are examples of raster files.

The map below is an example of raster data. Scanned maps must then be geo-referenced with accurate location data to align them with a map coordinate system.

Numeric Data

Numeric data is statistical data which includes a geographical component or field that can be joined with vector files so the data can be queried and displayed as a layer on a map in a GIS. An example of numeric data is an excel spreadsheet of  911 calls for service with location information. In this example location information is represented by longitude and latitude. However, location information could also be displayed using a street address or intersection.

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