the integration of geospatial technologies: gis and gps

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  • 1.INTEGRATED GIS/GPS TECH 1Running Head: INTEGRATED GIS/GPS TECHThe Integration of Geospatial Technologies: Geographic Information System (GIS) and Global Positioning System (GPS) Lindsey LandolfiTowson University Geographic Information Systems Applications:Homeland Security and Emergency ManagementProfessor John Morgan August 2011 Landolfi

2. INTEGRATED GIS/GPS TECH 2As we move from an industrial economy to a knowledge-based economy, our relianceon physical infrastructure is being supplemented by reliance on knowledge infrastructure, ofwhich geographic knowledge will form a key component. (Dangermond, 2010) The applicationof geographic information is pertinent to a wide range of users and purposes. Geospatialtechnologies such as the Geographic Information System (GIS) or the Global Positioning System(GPS) facilitate the implementation and exploitation of fundamental geographic data. Nationaland global federal agencies, state and local government, non-profit entities, private corporations,and academia implement enterprise applications and pervasive computing of geospatialtechnologies in order to develop strategy and support operations. It is important for governmentand public service organizations to develop and employ tools that most efficiently acquire andanalyze data. The use of integrated geospatial technologies can provide the best availableinformation to assist in decision making relevant to time and geography. This paper will providean overview of integrated geospatial technologies specifically the various methods of GIS andGPS integration, the benefits of integration, and provide real world examples of existingimplementations of integrated GIS and GPS applications. Geographic Information System (GIS) technology is used to inventory, analyze, manage,and display geodetic data as it is spatially referenced to the earths surface. GIS integrateshardware, software, and data in order to cartographically present layers of geographicinformation such as environmental, area, or demographic data. Each layer of spatial data islinked to corresponding tabular information. Layers can be combined and manipulated asnecessary; linking all layers to a mutual coordinate system enables maps of different scales andprojections to properly overlay. With GIS large quantities of data are combined into a singleobject-relational database enabling users to easily search for individual features and associated Landolfi 3. INTEGRATED GIS/GPS TECH 3attributes or identify patterns by examining the distribution of features. Numerous federal, state,and local governments, private and nonprofit organizations use GIS to enhance geographicknowledge. GIS is a powerful tool for planning and decision-making in operations dependent onor related to geographic information. For example, The Federal Emergency Management Agency(FEMA) uses GIS capabilities in disaster preparation and response. The access anddissemination of available geographic information is supported by the FEMA Mapping andAnalysis Center (MAC); in addition to managing a state-of-the-art GIS laboratory, the GIS staffengaged in GIS production and analysis for program offices throughout the Agency, including:the EST, the Readiness, Response and Recovery Directorate, the Federal Insurance andMitigation Administration, the Administration and Resource Planning Directorate, disaster fieldoffices, the Office of National Preparedness and Homeland Security. (FEMA, 2004) Global Positioning System (GPS) is a free international utility developed by the U.S.Department of Defense. GPS provides accurate space-based positioning, navigation, and timing(PNT) capabilities and services to GPS receivers.GPS data is continually transmitted via radiosignals from the satellites to GPS receivers. A GPS receiver will attempt to sync with the satellitesignal based off of a basic pseudorandom bit pattern. The receiver will delay the start of its bitpattern to coordinate with the satellite; the length of the delay is used to calculate the distancebetween the receiver and satellite. AGPS receiver and a minimum of three satellites arenecessary to perform a triangulation and accurately determine the users geographic position. SeeAPNDX figure 1 for an illustration of the interaction between GPS control, space, and usersegments. The GPS constellation is designed and operated as a 24-satellite system, consisting ofsix orbital planes, with a minimum of four satellites per plane. (Air Force Space Command,2010) See APNDX figure 2 for an illustration of the GPS satellite constellation arrangement.Landolfi 4. INTEGRATED GIS/GPS TECH 4This arrangement creates a robust and stable GPS constellation which guarantees constant accessto transmitting signals from at least four satellites to any location on the earth. Real-world datacollected by the FAA show that some high-quality GPS SPS receivers currently provide betterthan 3 meter horizontal accuracy. See APNDX figure 3 for GPS performance accuracyhistogram. The accuracy of data acquired by a GPS unit is influenced by the location and lengthan observation and the quality of a GPS receiver. All user-operated, satellite-based GPSreceivers comprise the user segment. The Air Force Space Command (AFSPC) monitors, andmaintains the GPS space and ground control segments. The GPS program is managed by TheNational Executive Committee for Space-Based Positioning, Navigation, and Timing (NEC-PNT), a military and civil interagency. NEC-PNT is responsible for developing, advising,coordinating, and overseeing the national PNT Strategy. NEC-PNT is co-chaired by the deputysecretaries of the Department of Defense and Transportation. Its membership includesequivalent-level officials from the Departments of State, the Interior, Agriculture, Commerce,and Homeland Security, as well as the Joint Chiefs of Staff and NASA. Components of theExecutive Office of the President participate as observers to the National Executive Committee,and the FCC Chairman participates as a liaison. (NEC-PNT, 2009) See APNDX figure 4 for anillustration of the NEC-PNT organizational structure. The Integration of GIS and GPS geospatial technologies couples GPS spatial positioningfunctionality with GIS ability to compute spatial relationships. GIS technology requires accuratefeature placement to best determine intricate spatial relationships. The GPS positional accuracyenhances the functioning of GIS by improving the spatial quality of GIS data. Typical sources ofGIS geographic information are field survey data, digitize graphical data, aerial photography,and satellite imagery. The integration of GPS as a spatial data source for GIS makes it possible toLandolfi 5. INTEGRATED GIS/GPS TECH 5successfully combine a features accurate geographic coordinates and the correspondingattributes and values of that feature. Layers from a GIS dataset can be geo-referenced andprojected to the GPS data coordinate system providing a unified spatial representation. Thecombination of GIS layers and GPS coordinates ensure integrity and consistency in the digitalrepresentation of reality. Integration of these technologies is economically sensible since accuratefield collection of data is time consuming and is subject to human error. Erroneousmeasurements must be re-acquired in the field. Also it may require multiple individuals to obtaina single measurement opposed to a single hand-held system user. Converting existing referencemaps requires accuracy confirmation which would traditionally bring uses back to the field forconfirmation. Overall, combing GIS and GPS technologies will increase worker productivity andefficiency. There are various techniques to integrate GIS/GPS. Data integration may occur between aself contained GPS and PC operated GIS; data is collected and stored in the field with GPS andlater transferred to the GIS database. An example of a data-focused solution is TrimbleNavigations GeoExplorer 3, for data collection and update, with GPS Pathfinder Office, fordata transfer and processing, and Esris ArcInfo or ArcView products, for spatial analysis, queryand archive. (Harrington, 2000) See APNDX figure 5 for an illustration of data-focusedintegration. Data focused interaction is a commonly employed method of integration. A tighterlevel of integration is a position focused approach; the concept is a GPS system will supplygeodetic data to a GIS field device. The field device will extract and store the data into the GISdatabase. Handheld devices that feature software application for both GPS control and GIS fieldoperations are becoming increasingly common. An example of position-focused integration isseen through the use of Trimble Navigations GPS Pathfinder Controller software to setup a GPS Landolfi 6. INTEGRATED GIS/GPS TECH 6Pathfinder XRS receiver for use with Esris ArcPad field-GIS product. (Harrington, 2000) SeeAPNDX figure 6 for an illustration of position-focused integration using a single or two fielddevices. Once connected to the Pathfinder XRS receiver ArcPAD will provide interface and datastorage while the GPS Pathfinder XRS still acts as the controlling device for the GPS receiver. The rapidly progressive field of software technology has paved the way for technologyfocused integration. This method is truly integrated as the GPS technology can be completelyembedded within a GIS application. Fully integrated GIS/GPS technology is based off of a geo-relational model which links spatial data files to data stored in the relational database. Control ofthe GPS hardware is executed directly by a GIS application allowing for total control of the GPSreceiver and two-way data flow. This method is advantageous since full GIS capabilities can betaken into the field. An example of technology-focused integration is the use of TrimbleNavigations Pathfinder Tools software development kit to integrate a GPS Pathfinder XRSreceiver within a customized application that uses Esris MapObjects product to visually displaya