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A Long-Range Dynamic GPS Processing System for Aircraft Navigation and Positioning 
Yanming Feng & Kurt Kubik, Queensland University of Technology, Australia 
Shaowei Han, The University of New South Wales, Sydney, Australia 
WG 1/2 - System Aspects of Platform Guidance, Navigation and Sensor Positioning 
KEY WORDS: GPS, real time dynamic positioning, Kalman filtering and smoothing, aircraft navigation and positioning. 
ABSTRACT 
On-The-Fly integer ambiguity resolution for long-range dynamic or kinematic GPS positioning is difficult to achieve. As a 
result, although quite a large number of originations have established their own versions of On-The-Fly software which has 
been very promising for short-range positioning, none has been successfully developed for long range dynamic GPS 
navigation and positioning. The paper documents a dynamic GPS processing prototype system that achieves decimetre-level 
accuracy in real time and 1ppm accuracy off-line (by postprocessing) in three dimensions over the range of a few hundred 
kilometres without OTF ambiguity resolutions. The prototype system was based on two important strategies. Firstly, it detects 
and removes any carrier phase cycle slips between two epochs in which there may be a data gap of a few seconds to a few 
minutes, depending on the user’s receivers and user‘s environments. Secondly, phase delta-positions and DGPS code 
positions are obtained without the needs of resolving ambiguities, which are then reprocessed in real time by Kalman 
filtering approaches to achieving decimetre accuracy, and off line by Kalman smoothing techniques for achieving 1ppm 
accuracy in three dimensions. This paper describes the theoretical basis of the developed long range dynamic GPS 
positioning system and gives experimental results for aircraft and navigation positioning, which confirm the achievable cycle- 
slip detectability and positioning capability. 
searching of ambiguity resolutions on the fly over lang 
ranges more difficult and even impossible. Thus, centimetre 
accuracy is difficult to achieve for long range applications. 
1. INTRODUCTION 
Much research has been done into fast and efficient ways to 
resolve carrier phase ambiguities, in order to enable GPS However, for aircraft guidance, navigation and sensor 
users to realise the maximum potential accuracy of GPS positioning for photogrammetry, real time decimetre 
carrier phase measurements. As a result, many accuracy and lppm accuracy off line in three dimensions 
organisations have developed their own versions of Over the range from a few tens to hundreds kilometres may 
kinematic GPS positioning software (Deloach et al, 1995), be quite acceptable. This may be achieved in theory without 
the majority of which is based on the so-called On-The-Fly On The Fly ambiguity resolutions (Feng, 1995; Cannon, 
(OTF) ambiguity resolution technique. OTF techniques 1995). On the other hand, the use of dual frequency carrier 
promise real - time centimetre positioning in three phase observable also makes it possible to detect and repair 
dimensions. However, almost all the existing systems were cycle slips depending on carrier phase measurements 
designed for short-range kinematic (or dynamic) positioning (Hofmann 1992; Han, 1995) rather than On-The-Fly 
environments, and none has so far been successfully techniques, which allow integer ambiguities to be resolved 
developed for long-range dynamic applications. There are again for kinematic process over short-ranges when a cycle 
two major reasons for this. The first reason is that for long- slip occurs. Our strategy for long-range kinematic or 
range dynamic or kinematic positioning, the integer dynamic positioning is therefore to remove cycle slips and 
ambiguity resolution is difficult to achieve from both realise decimetre accuracy in real time not depending on 
ionosphere-free and ionosphere biased carrier phase ^ OTF ambiguity resolutions. 
measurements. The ionosphere-free combination of L1 and 
L2 carrier phase measurements has the wavelength of a few The development of a long range dynamic (LRD) GPS 
millimetres; any other combinations of L1 and L2 suffer positioning system aims to provide a prototype system 
from the ionospheric effects. Thus integer ambiguities can capable of decimetre positioning in real time and lppm 
generally not be estimated in real time by the state-of the-art . — accuracy by postprocessing. This paper addresses the 
OTF techniques. The second reason is that the orbital errors theoretical basis for the LRD system and experimental 
and un-modelled troposphere effects on double difference results. Firstly, a method for cycle-slip detection and cycle- 
carrier phase measurements increase as the distance slip repair after data gaps are proposed, based on L1/L2 and 
between base and rover receivers increases (Chen, 1994). P-code measurements. This is followed by a method which 
These errors make integer removal of cycle-slips or integer jointly uses the code and phase measurements to create 
delta-positions and position sequences. These results are 
65 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996