Description
The UNB RTK system was initially developed for an auto-steering system for gantry cranes used in container ports. It is powered by the proprietary OMEGA (Optimal Method for Estimating GPS Ambiguities) ambiguity search engine and quality control algorithms. Two subsidiary tools support the system to attain ultrahigh performance GPS positioning and navigation:  (a) an optimal inter-frequency carrier-phase linear combination of the L1 and L2 measurements, and (b) receiver system noise estimation routine.

UNB’s OMEGA ambiguity search engine is based on the independent-ambiguity-search method. This uses the independent satellite group in establishing the ambiguity search space. Also, a modified Cholesky decomposition method computes the quadratic form of the residuals. Typically, OMEGA is able to find the first- and second-best ambiguity candidates out of a potential 1018 candidates within 0.1 second using a computer running a 486 Intel processor at 50MHz.

Unlike conventional approaches, the quality control routine of the UNB RTK system utilizes only the current epoch’s measurements (i.e., instantaneous cycle-slip correction). This yields high performance even when a receiver platform is maneuvering. Moreover, the quality control routine can handle cycle slips in low-quality measurements, so that it is not necessary to discard the measurements obtained at low elevation angles and from weak signals with low signal-to-noise ratios. This increases observation redundancy and improves system performance in terms of integrity, continuity, accuracy and satellite availability.

Potential Applications

Auto-guided vehicles and service robots are poised to enter the mainstream and users are beginning to derive significant benefits. Applications range from cleaning and lawn mowing to defense, rescue and security applications. The RTK GPS navigational system provides a smarter brain for new types of service robots which require fast, accurate and reliable auto-guidance. Testing suggests its performance is the best among a variety of RTK systems. The ultra high-performance, dual frequency UNB RTK system provides:

• Update rate of 10 Hz or higher;
• Positioning accuracy within two centimeters with a 99.99% confidence level; and
• System reliability of more than 99%.

State of Development
The technology has been commercialized.

Testing
The UNB RTK system has been tested on various platforms, including a PC (Dell OptiPlex, Pentium III, 540 MHz, WinXP) and the Motorola DSP56309 Evaluation Module (DSP56309EVM, 256 KB RAM) connected with the Bristol Aerospace SPP controller. The UNB RTK system has been successfully deployed in several industrial and scientific applications, including:

• Rubber-tired gantry cranes in daily use at the Korea International Terminals in Kawangyang Port (Korea, 2001-2002);
• Hybrid local deformation monitoring system at Highland Valley Copper Mine in British Columbia (Canada, 2003);
• Project for lengthening baselines by improving tropospheric modeling (USA, 2003-04);
• Enhanced Polar Outflow Probe in the GPS Attitude, Positioning and Profiling experiment for the Canadian multipurpose-satellite (CASSIOPE) now under development (Canada, 2003-present);
• Auto steering/auto positioning for container carrying vehicles currently under development (Korea, 2005 to present); and
• A platform for precision guidance applications including agriculture, pest control, row-crop spraying, forestry and fire fighting under development a world leader in precision GPS and differential GPS technology (North America, 2006 to present).

Additional Information
Dr. Donghyun (Don) Kim is a Senior Research Associate at the University of New Brunswick. He joined the Department of Geodesy and Geomatics Engineering in October 1998 as a post-doctoral fellow and has been a faculty member since October 2002. He has a B.Sc. in Urban Engineering; a M.S. and a Ph.D. in geomatics from Seoul National University. Prior to his current appointment, he worked at a number of universities, research institutes, and private companies.