A Geographic Information System (GIS) is a computer system that analyzes and displays geographically referenced information. It uses data that is attached to a unique location.
Most of the information we have about our world contains a location reference: Where are USGS streamgages located? Where was a rock sample collected? Exactly where are all of a city's fire hydrants?
If, for example, a rare plant is observed in three different places, GIS analysis might show that the plants are all on north-facing slopes that are above an elevation of 1,000 feet and that get more than ten inches of rain per year. GIS maps can then display all locations in the area that have similar conditions, so researchers know where to look for more of the rare plants.
By knowing the geographic location of farms using a specific fertilizer, GIS analysis of farm locations, stream locations, elevations, and rainfall will show which streams are likely to carry that fertilizer downstream.
These are just a few examples of the many uses of GIS in earth sciences, biology, resource management, and many other fields.
Related Content
Can I import a US Topo map into my Geographic Information System (GIS)?
Most Geographic Information System (GIS) vendors do not yet provide geospatial PDF import capabilities. US Topo maps are derived from GIS data sets and are formatted as PDF for the benefit of non-specialist users. We consider the product to be primarily an output of—rather than an input to—GIS. However, we recognize the demand for symbolized maps in GIS, and we are working on a companion product...
Are there metadata files for USGS topographic maps?
GeoPDF files for both Historical Topographic maps (produced 1884-2006), US Topo maps (produced 2009-present), and OnDemand Topo maps come with an XML metadata file attached to each GeoPDF file. To access the metadata file, download the GeoPDF file, open it in Acrobat Reader, click on the paperclip icon, then select a file from the list that appears (US Topo maps also come with a Map Symbols sheet)...
How are different map projections used?
The method used to portray a part of the spherical Earth on a flat surface, whether a paper map or a computer screen, is called a map projection. No flat map can rival a globe in truly representing the surface of the entire Earth, so every flat map misrepresents the surface of the Earth in some way. A flat map can show one or more--but never all--of the following: True directions True distances...
Related Content
- FAQ
Can I import a US Topo map into my Geographic Information System (GIS)?
Most Geographic Information System (GIS) vendors do not yet provide geospatial PDF import capabilities. US Topo maps are derived from GIS data sets and are formatted as PDF for the benefit of non-specialist users. We consider the product to be primarily an output of—rather than an input to—GIS. However, we recognize the demand for symbolized maps in GIS, and we are working on a companion product...
Are there metadata files for USGS topographic maps?
GeoPDF files for both Historical Topographic maps (produced 1884-2006), US Topo maps (produced 2009-present), and OnDemand Topo maps come with an XML metadata file attached to each GeoPDF file. To access the metadata file, download the GeoPDF file, open it in Acrobat Reader, click on the paperclip icon, then select a file from the list that appears (US Topo maps also come with a Map Symbols sheet)...
How are different map projections used?
The method used to portray a part of the spherical Earth on a flat surface, whether a paper map or a computer screen, is called a map projection. No flat map can rival a globe in truly representing the surface of the entire Earth, so every flat map misrepresents the surface of the Earth in some way. A flat map can show one or more--but never all--of the following: True directions True distances...
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