Application of Semi-Empirical TD Grid Calibration to the West Coast Loran-C Chain

摘要

This study demonstrates the utility of semi-empirical Loran-C time difference (TD) grid calibration techniques. Theory is employed to determine the functional dependence of TDs on range and bearing from the Loran-C chain stations. TD measurement data are then utilized to calibrate the unknown coefficients incorporated in the semi-empirical TD model. A semi-empirical model is presented for the West Coast Loran-C chain where at-sea TD measurement data in Southern California revealed large discrepancies between U.S. Coast Guard original predictions and measurements. A significant reduction in the TD errors is achieved with the semi-empirically-calibrated model relative to the U.S. Coast Guard original grid. The accuracy of the calibrated West Coast Loran-C grid is further evaluated by comparing the calibrated grid with measurements which are not used in model calibration. Results are also presented which show the sensitivity of the model accuracy to the quantity and distribution of measurement data used to calibrate the model. Guidelines are formulated to aid in the design of data collection requirements for future semi-empirical grid calibration efforts. (Author)