Research on the Loran-C Pseudorange Positioning Method Based on an Ellipsoidal Geodesic Model and Its Application in...

Area of Science:

• Geomatics Engineering
• Navigation Systems
• Geodesy

Background:

• The Loran-C system traditionally uses spherical hyperbola positioning (SHP), which introduces errors in inland regions due to Earth's ellipsoidal shape.
• SHP suffers from high geometric dilution of precision (GDOP) and difficulties in receiving signals from multiple stations in complex environments.
• These limitations restrict the application and development of Loran-C in inland areas.

Purpose of the Study:

• To address the limitations of the SHP algorithm in inland Loran-C applications.
• To introduce and evaluate the ellipsoidal pseudorange positioning (EPP) method.
• To improve positioning accuracy, coverage, and reliability for Loran-C in complex inland terrains.

Main Methods:

• Developed the ellipsoidal pseudorange positioning (EPP) algorithm, which accounts for Earth's ellipsoidal shape.
• Reduced the reliance on signals from a single Loran-C chain, enabling positioning with just three stations.
• Conducted simulation analyses and field tests using Loran-C chains in China, including inland mountainous regions.

Main Results:

• The EPP algorithm improved positioning coverage area by 129.1% to 284.6% compared to SHP in simulations.
• Field tests showed a significant reduction in root mean square error (RMSE) from 417.2 m (SHP) to 43.1 m (EPP), an 89.7% improvement.
• EPP effectively reduced GDOP and enhanced positioning accuracy and usable area in complex inland terrain.

Conclusions:

• The EPP method overcomes Earth ellipsoid modeling errors inherent in SHP.
• EPP significantly reduces GDOP, leading to substantial improvements in positioning accuracy and coverage.
• The EPP method provides reliable technical support for inland Loran-C navigation, timing, and backup applications.