Younsil Kim

DGPS Enhancement to GPS NMEA Output Data: DGPS by Correction Projection to Position-Domain

Most Differential Global Positioning System (DGPS) correction formats are based onrange information, and thus typical DGPS systems can be implemented only on correctionmessage-readable or raw observable-providing devices. There is no other way to improve analready-calculated position than a ‘block shift technique’, which has a very limitedapplicability. This paper suggests an algorithm to project measurement correction directlyto position domain data without requiring raw pseudorange data. By post-processingmethodology, we evaluated the performance of our newalgorithm compared to conventionalDGPS, which requires raw pseudorange data; the observed difference between them was only0·1mm . The proposed correction projection algorithm can be used with commercial off-the-shelf receivers that provide National Marine Electronics Association (NMEA) format data.Our testing with a U-blox LEA-5H receiver resulted in a drastic reduction of horizontal RootMean Square (RMS) error from 4·75m to 1·09m.KEY WORDS

GPS Cycle Slip Detection Considering Satellite Geometry Based on TDCP/INS Integrated Navigation

This paper presents a means of carrier phase cycle slip detection for an inertial-aided global positioning system (GPS), which is based on consideration of the satellite geometry. An integrated navigation solution incorporating a tightly coupled time differenced carrier phase (TDCP) and inertial navigation system (INS) is used to detect cycle slips. Cycle-slips are detected by comparing the satellite-difference (SD) and time-difference (TD) carrier phase measurements obtained from the GPS satellites with the range estimated by the integrated navigation solution. Additionally the satellite geometry information effectively improves the range estimation performance without a hardware upgrade. And the covariance obtained from the TDCP/INS filter is used to compute the threshold for determining cycle slip occurrence. A simulation and the results of a vehicle-based experiment verify the cycle slip detection performance of the proposed algorithm.

The study of error sources for MOSAIC/DME system: A single station based positioning system for APNT

This paper presents a new kind of navigation system, a single station based 3-dimensional positioning system, named MOSAIC/DME. Particularly, its possible error sources, such as tropospheric delay, antenna misalignment and multipath are studied and applied to simulations for understanding and verification of this system. For tropospheric and multipath simulations, WAAS tropospheric model and ray-tracing approach are applied respectively. The results present that MOSAIC/DME system is vulnerable to small errors in signal, because of the bad geometry using only a single station for positioning. But this system also has its own advantage to treat those errors.