Geographic Information Systems (GIS) technology has diverse applications, such as scientific investigations, resource management, and development planning. In the event of an oil spill in the ocean, GIS enables emergency planners to effectively calculate response times and impacted areas by taking into account the spill’s location. It is crucial to acknowledge that GIS is a computer system that gathers, stores, manipulates, and presents geographically referenced information – data distinguished by their locations. Additionally, GIS encompasses both the staff operating the system and the data utilized.
A geographic information system (GIS) operates by integrating data from various sources to determine the appropriate starting point for cleanup based on the duration of oil exposure. This is done by relating information about the location of an oil spill to surface currents of the oceans. A GIS can utilize information from diverse sources and forms, as long as the locations of the variables are known, denoted by x, y, and z coordinates of longitude, latitude, and elevation. Any spatially locatable variable can be input into a GIS.
Federal agencies and private firms are creating computer databases that can be directly incorporated into a GIS. Different types of map data can also be inserted into a GIS. Additionally, a GIS has the capability to convert existing digital information that is not yet in map form into a format it can interpret and utilize. For instance, digital satellite images can be analyzed to generate a map-like layer of digital data on marine life productivity. Similarly, sea-grass data can be converted into a map-like format to serve as thematic information layers in a GIS.
The next step in Geographic Information Systems (GIS) is data capture, which involves converting the data into a digital format that can be recognized by computers. There are different techniques for this process. One option is digitizing maps, where features are traced by hand using a computer mouse to collect coordinates. Another option is using electronic scanning devices to convert map lines and points into digital format.
A GIS can then analyze the spatial relationships among objects on the map. For example, while a computer-aided mapping system may only represent a shoreline as a line, a GIS can recognize it as the boundary between ocean and land and display tidal differences based on its location on Earth.
However, data capture in GIS work can be time-consuming as it requires specifying object identities and spatial relationships, as well as editing to correct errors in automatically captured information. Electronic scanners faithfully record blemishes along with map features, so any extraneous data must be edited or removed from the digital file.
Once the data is collected, it must be integrated using a GIS. The integration process is facilitated by the GIS, which can connect different pieces of information that would otherwise be challenging to associate. With its capabilities, a GIS can combine mapped variables and create new ones for analysis. Before analyzing digital data, additional manipulations may be necessary, such as projection conversions, to integrate the data into a GIS. Projection plays an essential role in mapmaking as it mathematically transfers information from Earth’s curved surface to a two-dimensional medium like paper or a computer screen. Different types of maps require specific projections suitable for their purposes. For example, while accurately representing continent shapes, a projection will inevitably distort their relative sizes.
GIS uses computers to transform digital information, sourced from maps with different projections, into a common projection. However, compatibility issues may arise when integrating seabed maps with satellite images of marine life. To address this, GIS can convert data from one structure to another. A marine life productivity map derived from a satellite’s interpreted image can be inputted into GIS as a raster file. Raster files consist of uniform cells encoded with data values. While raster files can be manipulated quickly, they may lack detail and visual appeal compared to vector files. Vector files represent data in points, lines, or shapes and can resemble traditional hand-drafted maps. GIS can perform data restructuring, such as converting a satellite image map into a vector structure by generating lines around cells with the same classification while determining spatial relationships between cells.A GIS enables the analysis of both seabed information and marine life information simultaneously. Traditional methods struggle to connect different data sets, but a GIS can illustrate the Earth’s surface, subsurface, and atmosphere in two or three dimensions based on data points.
GIS data is used in various ways, leveraging its power and usefulness. It allows for obtaining valuable information about the current state of different oceanic parts. With GIS, you can easily retrieve recorded information about a specific location, object, or area from off-screen files simply by “pointing” at it on the screen. By using scanned aerial photographs as a visual reference, GIS can provide insights into the geology or hydrology of various oceanic regions. Such analytical capabilities enable drawing conclusions about the environmental sensitivity of the oceans.
GIS technology can be valuable for choosing the optimal site. To demonstrate, the US Geological Survey (USGS) cooperated with the Connecticut Department of Natural Resources to digitize over 40 map layers related to the USGS Broad Brook and Ellington 7.5-minute topographic quadrangle maps. By employing GIS, this data can be manipulated and amalgamated to tackle planning and natural resource matters. Specifically, GIS was employed to identify a potential location for a new water well within a half-mile radius of the Somers Water Company’s service area. In order to conduct the analysis, digital maps of the water service areas were stored in the GIS. The GIS employed the buffer function to outline a half-mile zone around the water company’s service area. This buffer zone served as a “window” through which various map coverages relevant to well site selection were viewed and combined. The first step in identifying well sites was utilizing GIS to select undeveloped areas from the land use and land cover map. Developed areas were subsequently removed from consideration. In Connecticut, water quality in streams is closely monitored, and some streams within the study area are deemed unsuitable as drinking water sources. In order to prevent the extraction of water from these streams into the wells, 100-meter buffer zones were generated around them utilizing GIS, and these zones were plotted on the map. Furthermore, the map illustrating the buffered zone was merged with the land use and land cover map to exclude areas surrounding unsuitable streams from the analysis.The records from the Connecticut Department of Natural Resources document pollution sources, including their geographical location and textual descriptions of the pollutants. In order to steer clear of these hazardous zones, a 500-meter buffer zone was implemented around each point of pollution. This data was then utilized along with other relevant GIS layers to generate an updated map highlighting suitable areas for well sites.
The condition of the Earth’s surface, atmosphere, and subsurface can be assessed by inputting satellite data into a GIS. GIS technology enables researchers to analyze Earth processes over varying time periods, such as days, months, and years. For instance, by animating the changes in vegetation vigor during a growing season, it is possible to determine the most extensive drought period in a specific region. The resulting graphic, known as a normalized vegetation index, provides an approximate measure of plant health. By studying two variables over time, researchers can identify regional disparities in the time lag between a decrease in rainfall and its impact on vegetation. These analyses are facilitated by GIS technology and the availability of digital data on regional and global scales. The Advanced Very High Resolution Radiometer (AVHRR) is responsible for generating the vegetation graphic using satellite sensor output. This sensor system registers the amount of energy reflected from the Earth’s surface across various bands of the spectrum within approximately 1 square kilometer areas. The satellite sensor captures images of a particular Earth location twice daily. AVHRR is just one of numerous sensor systems utilized for analyzing Earth’s surface. More sensors will be deployed, leading to a greater accumulation of data. With this technology, scientists possess both the resources to aid in preserving our planet and evidence of global-scale destruction derived from GIS.
Magazine: GIS World October 98, February 99
Internet: www.gw.geoplace.com
Magazine: GIS Info Systems (Application of GIS and related spatial information technologies)
November 98, March 99
Internet: www.erdas.com
Magazine: GPS World January 98
Newsletter: URISA (Urban and Regional Information System Association)
Internet: www.geoinfosystems.com
Southwest Florida Management District is a government organization.
