What is a geographic information system (GIS)?

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.

8 Base Layers of The National Map

(Credit: Sexton, Pamela Ann. Public domain.)

 

 

 

Related Content

Filter Total Items: 4

How do I add a REST service on ArcGIS Server to TNM Viewer?

REST services on ArcGIS Server can be added with the following procedures: 1) Click the Add Data tool in the Advanced tab toolbar to open a dialog box. By default, the ArcGIS Server (AGS) service is selected. 2) Type (or copy and paste) an AGS REST service URL. Note that the URL should end in ".../ArcGIS/rest/services" without an ending "/". 3)...

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--...

Are there metadata Files for USGS topographic maps?

Yes. GeoPDF files for both Historical topographic maps (produced 1884-2006) and US Topo maps (produced 2009-present) 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 (a US Topo Map...

Can I import a US Topo map into my Geographic Information System (GIS)?

Most 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...
Filter Total Items: 1
Filter Total Items: 3
Date published: February 8, 2017

Imagery Services Update to The National Map

The USGS announces the sunset of National Map High Resolution Orthoimagery Data and Service

Date published: August 18, 2016

BLM, USGS Publish Data and Visualization Site for Sagebrush Geospatial Data

 

The Bureau of Land Management and the U.S. Geological Survey  have published a hub to enable easy visualization and access to geospatial data about the west’s “sagebrush sea.” This will help guide sagebrush conservation efforts during the 2016 fire season and beyond.

Date published: January 25, 2010

Volunteered Geographic Information for The National Map

The United States Geological Survey (USGS) sponsored a workshop on volunteered geographic information January 12-13, 2010 in Herndon, Va. The workshop explored how citizen mapmakers might contribute to The National Map, the USGS source for topographic information for the nation.

Filter Total Items: 4
8 Base Layers of The National Map
January 31, 2012

8 Base Layers of The National Map

8 Base Layers of The National Map

November 18, 2004

PubTalk 11/2004 — From Plane Tables to Pixels

The Revolution in Mapping at the U.S. Geological Survey

by Susan P. Benjamin, Research Geographer

  • Mapping the United States in the 19th century was arduous, dangerous work; flash floods, bears, and bandits were just a few hazards
  • By the mid-20th century, aerial photography, photogrammetry, and stereophoto pairs, allowed
...
Status map of The National Map Corps submitted structure edits as of November 30. 2018

Status map of The National Map Corps submitted structure edits as of N

Status map of The National Map Corps submitted structure edits as of November 30. 2018.