The explosion of consumer demand for geospatial information and tools such as geographic information systems (GIS) to manipulate and graphically display such information has brought GIS into the daily lives of millions of Americans, whether they know it or not. Google Earth and handheld or dashboard navigation systems represent enormously popular examples of the wide variety of applications made possible through the availability of geospatial information. The release of Google Earth in 2005 represented a paradigm shift in the way people understand geospatial information, according to some observers, because it offered multi-scale visualization of places and locations around the globe that was free and easy to use. This report provides a primer on geospatial data and GIS and provides several examples of their use. It should be recognized that the amount of geospatial data is expanding rapidly, the methods for acquiring geospatial data are growing, and the ways geospatial data are being used are diversifying throughout local and state governments, as well as within the federal government. It is beyond the scope of this report to present the universe of geospatial data and its utility to the federal government. However, the federal government has had and continues to have a major role in the overall framework for geospatial data, including its organization, coordination, and sharing among federal agencies and with state and local entities. In addition to providing basic information on GIS and geospatial information, this report describes the federal geospatial enterprise and how it is organized. Given the complexity of managing, sharing, and using geospatial data from a variety of sources and across the breadth of the federal government, the 112 th Congress in its oversight role may have an interest in the programs and geospatial "assets" belonging to most federal departments and agencies. CRS Report R41826, Issues and Challenges for Federal Geospatial Information , explores geospatial policy issues of interest to Congress, including organization and management, data sharing, coordination, the role of nonfederal stakeholders, and proposals for a national GIS, as well as examples of legislation. CRS Report R40717, Issues Regarding a National Land Parcel Database , delves into one specific federal responsibility: the coordination and management of land parcel data for all federal lands. Together, these three reports introduce basic concepts and discuss more complex policy issues regarding the federal geospatial enterprise. A discussion of classified geospatial information and national security issues is beyond the scope of this report. GIS is a computer data system capable of capturing, storing, analyzing, and displaying geographically referenced information—information attached to a location, such as latitude and longitude, or street location. Geographically referenced information is also known as geospatial information. Types of geospatial information include features like highway intersections, office buildings, rivers, the path of a tornado, the San Andreas Fault, or congressional district boundaries. Information associated with a specific location is referred to in GIS parlance as an attribute, such as the population of a congressional district, or amount of movement per year along the San Andreas Fault. Other terms common to geospatial data and GIS analysis are described in the box below. The power of GIS is the ability to combine geospatial information in unique ways—by layers or themes—and extract something new. For instance, a GIS analysis might include the location of a highway intersection and the average number of vehicles that flow through the intersection throughout the day, and extract information useful for locating a business. GIS might include both the location of a river and the water depth along its course by season, and enable an analysis of the effects of development on runoff within the watershed. Overlaying the path of a severe thunderstorm with geospatial data on the types of structures encountered—homes, stores, schools, post offices—could inform an analysis of what types of building construction can survive high winds and hail. Geospatial data may be acquired by federal, state, tribal, county, and local governments, private companies, academic institutions, and nonprofit organizations. The collection and management of geospatial data are considered by many to be the costliest components of a GIS—some experts attribute close to 80% of GIS total costs to data acquisition. Geospatial data can be acquired using a variety of technologies. Land surveyors, census takers, aerial photographers, police, and even average citizens with a GPS-enabled cell phone can collect geospatial data using GPS or street addresses that can be entered into GIS. The attributes of the collected data, such as land-use information, demographics, landscape features, or crime scene observations, can be entered manually or, in the case of a land survey map, digitized from a map format to a digital format by electronic scanning. Remote sensing data from satellites is acquired digitally and communicated to central facilities for processing and analysis in GIS. Digital satellite images, for example, can be analyzed in GIS to produce maps of land cover and land use. When different types of geospatial data are combined in GIS (e.g., through combining satellite remote sensing land use information with aerial photograph data on housing development growth), the data must be transformed so they fit the same coordinates. GIS uses the processing power of a computer, together with geographic mapping techniques (cartography), to transform data from different sources onto one projection and one scale so that the data can be analyzed together. Local and state governments provide geospatial data for use in GIS for a variety of public services such as land records, property taxation, local planning, subdivision control and zoning, and others. Local governments often contract with private-sector companies to acquire more recent and higher-resolution data than what is available to the federal government. Whether and how the most up-to-date and detailed geospatial information is made available to users other than the local government for which the data were acquired are long-standing issues. For example, in the immediate aftermath of a natural disaster, such as Hurricane Katrina in 2005, it may be important for the federal government to acquire the most current and detailed geospatial information about the disaster area. In many instances, however, impediments to data sharing such as lack of interoperability between systems, restrictions on use, concerns about data security, and a lack of knowledge about what data exist and where the data can be found could hinder a timely and effective emergency response. The federal government sometimes acquires geospatial data for federal needs, such as for updating floodplain maps from paper flood insurance rate maps to a digital format. Assessing the need to update floodplain maps on a periodic basis is required by law, and the Federal Emergency Management Agency (FEMA) has spent over $1.4 billion since FY2003 to convert paper flood insurance rate maps (FIRMs) to digital flood insurance rate maps (DFIRMs) and to produce a format usable in GIS. Simply converting paper maps to digital formats does not necessarily improve their accuracy, which often depends on the resolution of the original data. New techniques for collecting more data, such as Light Detection and Ranging (LIDAR), would help produce more accurate floodplain maps. Geospatial data are increasingly acquired and provided by the private sector, and many companies as well as professional organizations support and promote the role of private-sector data providers. One organization, the Management Association for Private Photogrammetric Surveyors (MAPPS), bills itself as the only national association exclusively composed of private geospatial firms. MAPPS itself is a member of a larger coalition—the Coalition of Geospatial Organizations (COGO). COGO is comprised of 11 organizations and associations involved in geospatial data and policy issues. The attributes of different types of geospatial data—such as land ownership, roads and bridges, buildings, lakes and rivers, counties, or congressional districts—can each constitute a layer or theme in GIS. (See Figure 1 for a schematic representation of data layers in GIS.) GIS has the ability to link and integrate information from several different data layers or themes over the same geographic coordinates, which is very difficult to do with any other means. For example, GIS could combine a major road from one data layer as the boundary dividing land zoned for commercial development with the location of wetlands from another data layer. Precipitation data, from a third layer, could be combined with a fourth data layer that shows streams and rivers. GIS could then be used to calculate where and how much runoff might flow from the commercial development into the wetlands. Thus, the power of GIS analysis can be used to create a new way to interpret information that would otherwise be very difficult to visualize and analyze. Timeliness is an important factor for some uses of geospatial information. An example is the southern California wildfires during 2008. One of the worst fires in the region, known as the Sylmar fire, began on the evening of November 14, 2008. It forced the evacuation of 10,000 people and shut down major freeways near the town of Sylmar on the edge of the Angeles National Forest. The speed of the fire's progress made it difficult to know where the fire was heading and to visualize escape routes. In addition, the fire jumped Interstate 210 (I-210) and Interstate 5 (I-5), two major routes of egress, on Saturday, November 15. To assist in real-time decision making, the fire's progress was posted on the Internet in near real-time by several organizations, using reports from the ground, and the information about the fire was displayed on underlying street maps (showing where the fire crossed I-5 and I-210), terrain maps, and satellite images. (See Figure 2 .) The Sylmar fire example underscores the informational power available when geospatial information is combined with tools for displaying the information, such as GIS and the Internet.