Geospatial Analysis

Introduction

Geospatial analysis in environmental science refers to the use of geographic data to identify environmentally relevant information that is referenced to geography and that can also be referenced to time. Four examples are the detection of environmental hazards, monitoring the spread of pollution over time, analysis of trends in environmental parameters such as temperature and ocean acidity over time, and to associate various environmental parameters with locations (such as droughts with geographical location).

More specifically, geospatial analysis is the manipulation of data based on location. This kind of analysis uses tools including geographic information systems (GIS), global positioning systems (GPS), georeferencing, metadata (“data about data”), and remote sensing. It can be used, for example, to probe the distribution of an air pollution event such as the accidental release of radioactive material or another toxic substance into the air, and to reveal contaminated wells in a region in an investigation of the contamination of groundwater.

Historical Background and Scientific Foundations

Geospatial analysis dates back to the early 1960s, when the Canadian Land Inventory project—a complex land use analysis involving about 1 million mi (1.6 million km) of Canadian inhabited and economically relevant territory—utilized computer mapping software in compiling, manipulating, analyzing, and displaying the information. Prior to this, such a project was done literally by hand. This project represented the origin of GIS.

At about the same time, satellites were beginning to be used to acquire information based on energy of different wavelengths that are emitted from Earth’s surface. This technology (remote sensing) enables information to be gathered from large tracts of land and water at different regions of Earth using orbiting satellites, and information from one region over time using satellites that remain in the same position (geosynchronously orbiting satellites). Also, a system of at least 24 satellites positioned in various orbits 11,000 mi (17,703 km) above the surface of Earth provides a global navigation system, in which any position of the surface of the planet can be determined in any weather; this is the GPS (also called the NAVSTAR). The accuracy of nonmilitary positional determination is within 109.3 yards (100 m), and can be within 10.9 yards (10 m). The military version of GPS permits accuracy to within 3.2 ft (1 m).

Geospatial analysis makes use of these technologies to geographically analyze data. Spatial data on the geography of Earth can be combined with other GIS, remote sensing, of GPS data to make associations between a particular parameter of interest and geography. Using data obtained at different times allows these associations to be studied over time. For example, data on the acid precipitation known as acid rain has been combined with data on the pH and biological diversity of freshwater lakes to indicate the effects of acid rain on natural ecosystems from the 1970s onward, and the geographical spread of the effects of acid rain.

Geospatial analysis is concerned with what are known as data layers. This refers to various data that can be visually overlaid to generate an image that incorporates all the information in a way that is meaningful. An example of data layers is an image of California that depicts all land being used for agriculture on which is overlaid locations of contaminated groundwater. Such an image would be useful in helping reveal the influence of agricultural chemicals on water quality.

Another geospatial analysis tool is georeferencing. This refers to the assignment of a feature of interest (e.g.,

WORDS TO KNOW

ECOSYSTEM: The community of individuals and the physical components of the environment in a certain area.

GEOGRAPHIC INFORMATION SYSTEMS (GIS): A set of computer-based tools that collects, analyzes, and maps spatial data.

GLOBAL POSITIONING SYSTEM (GPS): A system consisting of 25 satellites used to provide highly precise position, velocity, and time information to users anywhere on Earth or in its neighborhood at any time.

hazardous waste sites) to the particular geographic region.

Impacts and Issues

In environmental science, geospatial analysis is useful in revealing linkages between environmental hazards and potential exposures to the hazards. Furthermore, the ability to compile the information over time can reveal changing environmental conditions that can expose

development of a potentially hazardous situation as well as changing climatic conditions.

A recent example of the power of geospatial analysis was a 2008 study published in the journal Science, in which a variety of information on ocean chemistry, temperature, biodiversity, and other factors was used to create a global map depicting ocean degradation. The study revealed that over 80% of the ocean has been affected by human activities that include overfishing, runoff of agricultural pesticides and urban-generated sewage from coastal regions, and pharmaceuticals. Being able to visually display the extent of human-mediated ocean deterioration has spurred resolve to better manage ocean health.

In another example, geospatial analysis was used in a study undertaken in Alameda County, California, by the Centers for Disease Control and Prevention (CDC) to relate traffic volume to health indicators of asthma and reproductive problems. This sort of environmental heath analysis was useful in highlighting the influence of vehicle exhaust on health. The CDC’s Public Health Information System and the National Electronic Disease Surveillance System are undertaking other geospatial analysis studies to acquire more environmental health information.

See Also Biostratigraphy; Geographic Information Systems (GIS); Maps and Atlases; Surveying

BIBLIOGRAPHY

Books

Bolen, Eric, and William Robinson. Wildlife Ecology and Management. New York: Benjamin Cummings, 2008.

Chiras, Daniel D., John P. Reganold, and Oliver S. Owen. Natural Resource Conservation: Management for a Sustainable Future. New York: Prentice-Hall, 2004.

Kidd, J. S., and R. A. Kidd. Air Pollution: Problems and Solutions. New York: Facts on File, 2005.

Periodicals

Halpern, B. S., et al. “A Global Map of Human Impact on Marine Ecosystems.” Science 319 (2008): 948–952.

Web Sites

National Aeronautics and Space Administration(NASA). “Ozone Hole Watch” October 4, 2004. http://ozonewatch.gsfc.nasa.gov/facts/hole.html (accessed May 2, 2008).