Integrating mobile mapping, GPS and GIS technologies

Abstract

A detailed definition of Global Positioning System (GPS) as given by Wooden 1985]reads: ?The Navstar Global Positioning System (GPS) is an all weather, space basednavigation system under development by the U.S. Department of Defense (DoD) tosatisfy requirements for the military forces to accurately determine their position,velocity, and in a common reference system, anywhere on or near the earth on acontinuous basis?.Despite the main military goal of GPS, it has attracted a broad spectrum of users.Moreover, it has become an essential component of various applications ranging fromsurveying and mapping as well as precise time determination, vessel navigations andoceanography to international air traffic management [Parkinson et al., 1994].Basically, GPS is comprised of three main segments: the space segment, the controlsegment and the user segment. The purpose of these segments is to provide continuousreliable positioning and timing services for GPS users. The space segment consists of 24satellites orbiting around the earth at an altitude of about 20200 km and with a period ofApproximately 12 hours as illustrated in Figure 2.1 [Hoffmann-Wellenhof et al., 1994].Each satellite transmits a signal that includes the navigation messages based onand GIS industries to apply it in order to obtain high flexibility in data acquisition, moreinformation with less time and effort, and high productivity. In addition, a successfulExtension of this technology to helicopter - borne and airborne systems will provide apowerful tool for large scale and medium scale spatial data acquisition and databaseupdating. This thesis provides a systematic introduction to the use of mobile mappingtechnology for spatial data acquisition. Issues related to the basic principle, dataprocessing, automation, achievable accuracies and a break down of errors are given.Application considerations and application examples of the technology in highway andutility mapping are described. Finally, the perspective of the mobile mapping technologyis discussed.periodically uploaded data from the control segment. The control segment is a set ofmonitor stations, ground control stations, and a master control station (that is the centralcontrol node for GPS operations) and backup master control station. The user segmentconsists of GPS receivers from wide varieties of manufacturers. These receivers processThe received GPS signals and compute the user position.The GPS reference coordinate system is the World Geodetic System 1984 (WGS-84)[Decker, 1986]. The user?s coordinates are determined in this frame and can then betransformed to other systems. Timing is the heart of GPS; GPS time uses an atomic timescale. GPS time is defined as the number of seconds elapsed from Saturday midnight ofthe present week. The GPS time was coincident with Universal Time Coordinated (UTCis maintained by the U.S. Naval Observatory USNO) at the GPS standard epoch ofJanuary 6, 1980.GPS time is synchronized with UTC at the microsecond level, within an integer numberof seconds. The integer offset between GPS time and UTC arises because of the leapseconds periodically inserted for UTC [Hoffmann-Wellenhof et al., 1994].Fundamentals of GPS signal structure, observations and error sources, as well as a briefhistory of the Global Positioning System, Segments of the GPS, A primer on how theGPS works, Problems with the GPS, Advancements in the GPS are presented in thefollowing sections. These fundamentals are directly relevant to the research presented inthis thesis.Mobile mapping has been the subject of significant research and development by severalResearch teams over the past decade. A mobile mapping system consists mainly of amoving platform, navigation sensors, and mapping sensors. The mobile platform may bea land vehicle, a vessel, or an aircraft. Generally, the navigation sensors, such as GPS(Global Positioning System) receivers, vehicle wheel sensors, and INS (InertialNavigation System), provide both the track of the vehicle and positional and orientationalinformation of the mapping sensors. Objects to be surveyed are sensed directly bymapping sensors, for instance CCD (Charge Coupled Device) cameras, laser rangers, andradar sensors. Since the orientation parameters of the mapping sensors are estimateddirectly by the navigation sensors, complicated computations such as photogrammetrictriangulation are greatly simplified or avoided. Spatial information of the objects isextracted directly from the georeferenced mapping sensor data by integrating navigationsensor data. Mobile mapping technology has evolved to a stage which allows mapping