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GIS Help
What is GIS?
A geographic information system is a system designed to capture, store, analyze, and manage data and attributes that are spatially referenced to Earth.
What is GIS used for?
GIS encompasses a wide variety of uses including but not limited to scientific investigations, asset management, environmental assessment, urban planning, marketing, and cartography. In its most basic form, GIS is great tool to create, analyze, and view maps.
What is GIS data?
GIS data represents real world data with digital data. Two methods are used to store data in a GIS: Vector and Raster. The vector data model represents each feature as a row in a table, and feature shapes are defined by x,y locations in space (the GIS connects the dots to draw lines and outlines). Features can be discrete locations or events, lines, or polygons. In the popular GIS software ESRI ASrcGIS, these are called shapefiles.
The raster data model represents features as a matrix of cells in continuous space. Each layer represents one attribute (although other attributes can be attached to a cell). Most analysis occurs by combining the layers to create new layers with new cell values. Raster data is stored in various formats; from a standard file-based structure of TIF, JPEG, etc.
Most of the GIS files contained in our website are raster images that have been geo-referenced. The zipped files contain the TIFF image, a world file and other files that contain geospatial data to be used by a GIS application to correctly open the map in its intended geographic location on Earth.
What is a geo-referenced image?
Georeferencing is the process of establishing a relationship between an image ( such as a historic image that has been scanned and converted to TIFF or JPEG) and real world known coordinate points. Using applications such as GIS, an image is overlayed over a base map and control points are used to fix the image to its relative locations on the base map, thus giving the scanned image its exact geographic location on the Earth surface according to the datum and projection of the base map.
What do I need to view GIS files?
In order to open and view the GIS files you must first download ArcExplorer, a free GIS application available through ESRI.
How do I open and view the GIS files?
Click on the GIS file link of the selected map and proceed to unzip the file. You can save all your unzipped GIS files in a folder on your computer. Open the ArcGIS Explorer and click on the add layer button. In the new window called catalog, change file type to image files and proceed to look for the folder containing the unzipped GIS files in the table of content. Clicking the file you want to add will bring it up on the main screen of the catalog window, you then highlight the file or files you want to add and click the add file button located on the top left of the catalog window.
How do I use AEJEE?
For video tutorials on installing and using AEJEE (ArcExplorer—Java Edition for Education), please see our Tech-Ease website.
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