Geographic Information Systems (GIS)

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ISU GIS Facility - The GIS Support and Research Facility is a public computing facility established to support the use of geographic information system (GIS) technology at Iowa State University. The mission of the facility is to provide a high level GIS research support laboratory for students, faculty and staff as well as to provided GIS education and outreach to the ISU community and the state of Iowa.
    Iowa Geographic Map Server

Map and GIS Data By US State
DRGs By State/Territory
DRGs Available Free Online
GSTC Geospatial Data Clearinghouse
Geospatial Freeware

Doyle's GIS Links Web Page - From these web pages you can download Aerial photographs (DOQs), Topographic Maps (DRGs), Digital Elevation Models (DEMs), Digital Line Graphs (DLGs) and other GIS info.

Environmental Systems Research Institute, Inc. (ESRI) - designs and develops the world's leading geographic information system (GIS) technology. GIS is an important tool--one that helps shape the world around us.
    Site Map

GIS Data Depot - Free GIS Data  
    GIS Data - USGS Quad Grids - Nationwide (US)
    GIS Data - by State
    Index Maps

USGS Resources
    Locator Map(s) (CONUS)
    Digital Raster Graphics (DRG)
    Search USGS by State

MacGPS Pro - One of the advantages of MacGPS Pro is its ability to use digital maps from a wide variety of sources. We have compiled a current sampling of digital maps as a starting point to help you find the right maps for your application. This is by no means an all inclusive list, but we will continue to monitor and update this list on a regular basis to serve as a resource for the GPS community. If you find an error or broken link in this list, please let us know so it can be updated. We value your feedback as our customer and will continue to strive to meet your needs.

While some of these maps are free for downloading, others are available for various fees. Some are supplied over the Internet; others are supplied on CDROM. As we have no affiliation with these organizations and have not verified that all maps from these sources are compatible with MacGPS Pro, it is the customer's responsiblity to verify that any map purchased is in a format that MacGPS Pro can use.

GPSy (TM) Digital Map Support - A comprehensive (we haven't seen one that's more extensive) list of all of the digital maps available on the internet.

Graphical Locater Home Page - The positional accuracy of Graphical Locater is limited by the pixel size (reported with every location), the users aim (unknown), and the underlying map data (+/- about 50 meters for the 1:100,000 map data). The program introduces no error of its own, as far as I know. Graphical Locater results are better than any other method available to me, so I have no way to independently test its accuracy, others are invited to do so and report back. The median absolute difference between Graphical Locater elevations and the elevation reported for over 30,000 named places in the us_concise file of the GNIS was 5.5 meters. Of the 10 largest errors, all were in the name file. As with all grid interpolations, the elevation of peaks will be low and the elevations of dips will be high. The roughness gives a measure of the point elevation uncertainty.

National Geodetic Survey Data Sheets - Information about survey monuments on record with the National Geodetic Survey (NGS) is published in a Digital Survey DATA (DSDATA) format. The format consists of fixed field records in an 80 column ASCII text file.

Documentation and Tools for Utilizing USGS Digital Raster Graphic Data

Geodetic Coordinates From Maps
    Wikimapia (coordinates in url)
    USGS National Map Viewer
    Graphical Locater (map)
    Latitude/Longitude Position Finder

Finding Coordinates from Maps and Orthoquads
    MSR Maps
    USGS National Map Viewer



Copyright 2010 - Samuel J. Wormley