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In the network-based real-time kinematic (RTK) global positioning system approach, the rover positioning accuracy and reliability depends on the quality of the atmospheric corrections, which is largely a function of spatial and temporal variability of ionospheric and tropospheric parameters. The location of the rover receiver with respect to the reference network receivers is also a very important factor, especially for applications such as off-shore navigation, where favorable geometry cannot always be assured. The primary goal of this paper is to describe tests of the speed and reliability of the ambiguity resolution and the ultimate accuracy of kinematic positioning for two representative reference receiver geometries: (1) pentagonal reference receiver geometry, with network-rover separation up to 131 km, which represents a typical reference scenario where the rover is located inside the reference network; and (2) irregular geometry, simulating a shore-bound scenario where the reference network can support only extrapolation of the atmospheric corrections to an off-shore rover (outside the reference network), with network-rover separation up to 200 kin. The latter scenario is of special interest here, as the objective is to investigate the maximum acceptable separation of the rover receiver from the shore-bound reference stations. The Ohio Continuously Operating Reference Stations (CORS) network is used to simulate both scenarios, and the MPGPS software developed at The Ohio State University Satellite Positioning and Inertial Navigation Laboratory is used to carry out the analyses over a 24-h period of varying ionospheric activity. As a result of this study, the error budget associated with both network geometries is obtained, and the limitations of the network approach as a function of the network-rover geometry can be ascertained. DOI: 10.1061/(ASCE)0733-9453(2009)135:3(90) CE Database subject headings: Global positioning; Geodetic surveys; Accuracy; Statistics: Geometry; Ohio; Kinematics.

Fast and reliable ambiguity resolution (AR) is particularly challenging in long-range real-time kinematic (RTK) global positioning system (GPS), since the atmospheric errors decorrelate with the increasing base-rover separation, effectively reducing the success rate of integer fixing. In order to improve the speed and the success rate of AR, external atmospheric corrections are required. In this paper, four different methods of ionosphere modeling are used as a source of external information, and their impact on the speed and reliability of AR and the rover positioning accuracy is discussed. An example data set, collected by the Ohio Continuously Operating Reference Stations on August 31, 2003, is analyzed, with special emphasis on varying ionospheric conditions during the course of the day in order to study the applicability of these ionospheric models to high-accuracy RTK GPS. In particular, the time-to-fix, the level of AR success, and the accuracy of the resulting rover coordinates are analyzed. Each method displays a different level of accuracy, and thus varying applicability to support AR under changing ionospheric conditions. DOI: 10.1061/(ASCE)0733-9453(2007)133:2(56) CE Database subject headings: Global positioning: Errors; Networks; Reliability.

Today's mobile mapping systems (MMS) benefit from an array of sensors and technologies to collect precise data on roadways. Data collected by MMS include spatial and attribute information on various objects of interest. The global positioning system (GPS), usually differentially corrected, is one of the essential positioning technologies currently used in MMS, which is often integrated with other positioning technologies, such as inertial navigation systems (INS), differential odometers, and digital compasses. As GPS is the most dominant positioning technology in MMS, we propose an innovative approach in utilizing GPS in order to improve its performance and productivity, and to reduce the operational costs of MMS. To that end, we present and discuss in this paper GPS quality of service (QoS) and a novel approach called GPS QoS MAP (GQMAP) to reliably predict optimal data collection strategies using MMS. KEYWORDS: Mobile mapping systems, GPS, GPS quality of service, Mobile Mapping Systems: Overview Grejner-Brzezinska (2001a) defines a mobile mapping system (MMS) as a kinematic platform providing a basis for multiple imaging and positioning sensors, integrated and synchronized to a [...]

This paper deals with the issue of incorporating pseudolite measurements into an integrated Global Positioning System/ Inertial Navigation System (GPS/INS) positioning and attitude system with a view to improving signal availability, solution reliability, and accuracy in a localized area. Existing GPS/INS systems can overcome inherent shortcomings of each of the navigation technologies (line-of-sight signal requirement for GPS and INS errors that grow with time); therefore, such systems are now used for a wide variety of land, sea, and airborne applications where accurate positioning and/or attitude information is required with high output rate. However, their performance can still be degraded under certain conditions, such as when the duration of satellite signal blockage exceeds a certain time period (related to the quality of the INS), resulting in large accumulated INS errors. Such a scenario is a common occurrence for many kinematic applications. In an integrated GPS/Pseudolite/INS scheme, in order to gain the maximum benefit from additional pseudolite measurements, it is necessary to investigate how pseudolites can best be deployed to complement an existing GPS/INS system. A series of simulations, as well as field experiments with a GPS/Pseudolite/INS system comprising a Nov Atel Millennium GPS receiver, an IntegriNautics IN200 pseudolite, and a MIGITS strapdown INS, were carried out, and the impact on performance of integrating pseudolite(s) has been assessed for a variety of operational conditions and different system configurations. The results indicate that the overall performance of the system can indeed be significantly improved using additional pseudolite measurements. CE Database subject headings: Global positioning; Navigation; Integrated systems; Estimation.