This report compares predictions of groundwave propagation time with experimental values. The prediction methods included an integral equation technique that accounts for both terrain and impedance variations, a method developed by J.R. Wait that accounts for impedance variations, and Millington's or Pressey's technique that accounts for inhomogeneous impedance. Experimental incremental time-of-arrival data were acquired between eight sites along a propagation path from Search-light, NV. to Ft. Cronkhite (near San Francisco Bay). The major conclusions reached from the analysis and comparison of results are: terrain variations produce significant local and cumulative phase variations, in this case, a cumulative large increase in total secondary phase; impedance values need to be known to within less than a factor of two to be sufficient for preparing charts for navigation in restricted waterways; a priori definition of terrain variation can be performed with required accuracy - a priori definition of surface impedance values with sufficient accuracy is unlikely without supporting measurements; and a combination of predictions and measurements is required for accurate chart preparation. Predictions can be used to define appropriate measurement locations and to interpolate between measurement values. (Author).

The geophysical data available for a select propagation path for use in the study of the propagation of a Loran-C pulse is evaluated and recommendations for the initial estimates of ground geoelectric section resistivities is presented. A new rigorous technique for the computation and prediction of loran time difference coordinates from loran receiver geographic coordinates and visa versa is introduced by application to a specific loran overland situation. The full wave theoretical transient solution for the Loran-C pulse is employed. An experimental program to validate the theoretical transient solution for the Loran-C pulse is presented.