Because many organizations need similar datasets, there has been a special emphasis on the development of web based repositories for searching and finding geographic data. Crucial to this effort is the concept of "metadata."
Metadata is often defined as "data about data." Metadata is essential because it is information about a particular dataset: things like who created it, when was it created, why was it created, rules for its use, what time point(s) it represents, etc. Note that metadata is important for geographic and nongeographic datasets. It would be impossible to share data without metadata. Keep this in mind from now on. Documenting your data will be a key part of your GIS work.
In the United States, the Federal Geographic Data Committee (FGDC) has made a major effort to develop standards for the development of GIS metadata.
The GeoData Alliance also works on enabling the creation, flow, and beneficial use of geographic information.
Other organizations and companies have developed tools that have become standards. Galdos Systems, Inc., for example, has become a leader in Geography Markup Language (GML), an XML application that is becoming the world standard for geographic information delivery over the Internet.
In the USA, collection of metadata is often required for agencies or research programs that receive federal funding.
There a numerous web sites that provide access to metadata (and often freely shared datasets themselves). The gradual existence of metadata is providing the capacity to search the web for GIS data much more easily. There is a collection of internet servers responsible for storing and sharing metadata listed below.
The Federal Geographic Data Committee coordinates the sharing of geographic data, maps, and online services through an online portal for domestic data (US): Geospatial One-Stop, that searches metadata held within the NSDI Clearinghouse Network. Take a few minutes to explore this website and search for data. For example, you might want to try searching for topographic information on Amherst, MA USA.
The Clearinghouse Network is a community of distributed data providers who publish collections of metadata that describe their map and data resources within their areas of responsibility, documenting data quality, characteristics, and accessibility (US and International data). You can try to find some data, but DO NOT search all clearinghouse servers. Just choose a couple. For example, you might try to see what kinds of data are available for Africa, by selecting the "African Data Dissemination Service" and/or the "African Geospatial Data Sets" option.
Global Spatial Data Infrastructure Gateway makes access to geospatial information possible as well as making it possible to publish your own geospatial data. NOTE: We had some periodic problems accessing this server]
The Global Spatial Data Infrastructure Association "...is an inclusive organization of organizations, agencies, firms, and individuals from around the world. The purpose of the organization is to promote international cooperation and collaboration in support of local, national and international spatial data infrastructure developments that will allow nations to better address social, economic, and environmental issues of pressing importance." There are news letters and discussion lists, including ones focusing in on particular regions of the world, such as Africa.
Go to Geography Network where you can find many types of geographic content including dynamic maps, downloadable data, and more advanced Web services. It is a service from the commercial GIS software company ESRI.
You can enter a key word (Amherst, MA, for example) and search available data in a given category (e.g. environmental).
Explore the ways in which you can access information clicking in the tabs: web services, data, maps, etc. Have a look at the option of getting "dynamic data and maps". This is one direction GIS is moving -- utilizing data that is maintained by the data owner and accessing it in real time over the Internet.
The below provides a list of other portals and GIS resource sites that we are aware of.
The Center for Spatially Integrated Social Scienceshttp://www.csiss.org/
The GIS Data Depot http://data.geocomm.com/. Has data for US states and counties (some of this data is free, some must be purchased)
The ESRI guide to GIS http://www.gis.com/index.cfm
The GIS Portal http://www.gisportal.com/
GIS and remote sensing educational materials and tutorials http://www.photogrammetry.ethz.ch/general/persons/jana/isprs/ed_material.html
UMASS Open GIS curriculum project link page with quick access to the most important open source GIS programs.
Massachusetts GIS information about GIS around the world http://www.mass.gov/mgis/giswww.htm
University of Edimburgh GIS WWW resource list http://www.geo.ed.ac.uk/home/giswww.html
University of Texas's useful Internet sites for GIS and water resources http://www.ce.utexas.edu/prof/maidment/gishydro/docs/websites/othr_web.htm
USGS GIS data for water resources http://water.usgs.gov/maps.html
WMS Sites, a catalog of public web mapping service resources online. http://wms-sites.com/
There are lots of GIS and map sources available using US Federal websites, although most data is now accesible through the Geospatial One-Stop that we visited earlier. Some of those sites keep data on other countries in addition to the US.
Take some time to take a look at these sites, and perhaps try searching for something of interest to you.
http://seamless.usgs.gov/ Seamless Data Distribution System, Earth Resources Observation and Science ? (EROS). Here you can download seamless US and global data for a given geographical area that you select interactively. It is VERY useful to obtain elevation data (DEM) at different resolutions, as well as land cover, transportation, hydrography, orthoimagery, boundaries and national atlas data.
http://redhook.gsfc.nasa.gov/~imswww/pub/imswelcome/ The NASA Earth Observing System Data Gateway. A portal for U.S. NASA data.
http://edcsns17.cr.usgs.gov/EarthExplorer/ The USGS EarthExplorer site. A tool to query and order satellite images, aerial photographs, and cartographic products through the USGS. As an example, this is how you would do a search on available Landsat satellite images for the Amherst, MA region:
Enter as GUEST
Click on define on map
Zoom in to your geographic area of interest.
Select the types of datasets you are interested in. Let's just select Landsat for this exercise.
Press continue
Select the acquistion date or temporal range you are interested in.
Press search
Click on the hyperlink that is returned to see the list. You can browse available images, look at their previews and footprints, and details about their quality.
http://www.census.gov/ US Census Bureau website. Note the "Geography" option and the reference to "Tiger files". These are GIS layers related to census data (such as various census geographic boundaries).
http://www.nationalatlas.gov/atlasftp.html The U.S. National Atlas. Provides abundant US data, for example:
Agriculture: Agriculture Census 2002 - Crops, Expenses, Farmland...
Biology: Bat Ranges, Butterflies, Forests, Invasive Species, Land Cover...
Boundaries: Congressional Districts, Counties, Federal lands, States...
This is one location where students in the US can get congressional boundaries in GIS format.
Climate: Precipitation, Hazard Events, Hurricanes, Sea Temperature...
Environment: Air Releases, Hazardous Waste, Toxics Release...
Geology: Earthquakes, Landslides, Shaded Relief, Volcanoes...
History: Presidential General Election 2000 County and State Results.
Map Reference: Cities and Towns, Urban Areas...
People: Census, Crimes, Energy Consumption, Mortality...
Transportation: Airports, Parkways and Scenic Rivers, Railroads, Roads...
Water: Aquifers, Dams, Watersheds, Streams and Waterbodies...
Non-GIS data can be linked as secondary data to any GIS layer, enhancing the power of GIS analysis. In other words, you may often have a need for some data that are not currently associated with a GIS layer, but could be. For example, suppose you were interested in summary statistics for a c?rtain public health problem for each U.S. State. If you could find that summary statistical data in some kind of tabular or spreadsheet format and having for each row its associated state, you could "join" this data to a polygon layer of US states. Once done, you could do various queries looking at the geographic pattern of this issue across the U.S. at the state level of aggregation.
Some examples of useful websites for data sets that are not necessarily GIS layers:
Social and economic statistics
Statistics and Social Science Data at the University of Virginia http://fisher.lib.virginia.edu/collections/stats/
FEDSTATS: The U.S. Federal Government main statistics portal. More than 100 agencies contribute their data to this site. http://www.fedstats.gov/
The US Census Bureau site http://www.census.gov/
Biodiversity
The Global Biodiversity Information Facility http://www.gbif.org/
HerpNet http://herpnet.org/
The Mammal Netowrked Information System at UC Berkeley http://manis.mvz.berkeley.edu/pres/PresentationServlet?action=home
The Ocean Biogeographic Information System http://www.iobis.org/Welcome.htm
The Ornithological Information System http://ornisnet.org/
The System-wide Information Network for Genetic Resources http://singer.grinfo.net/. A database of crop, vegetable and agroforestry information.
The United National Environment Program http://na.unep.net/datasets/datalist.php