Analyses of the geolocation accuracy that can be obtained from shipborne sensors by use of time difference of arrival (TDOA), scanphase, and angle of arrival (AOA) measurements

We have performed a theoretical study of the geolocation accuracy that can be obtained from shipborne sensors by use of the localization methods: 1) time difference of arrival (TDOA), 2) scanphase, and 3) angle of arrival (AOA). Each method has been studied separately and in combination with the other methods. Several sensor geometries and types of movement have been investigated. Software for the simulations was written in Matlab v7.7. The simulations showed that geolocation accuracies of about 5 m at 10 km distance and 100 m at 50 km distance from the sensors could be obtained after 15 min of observations with two sensors. The emitter was assumed to be stationary during the observations. If only one sensor was used, the corresponding accuracies were 100 m and 3000 m. Momentaneous geolocation could be obtained if two or more sensors were used. With four sensors the geolocation accuracy was then found to be approximately 40 m at 10 km distance and 800 m at 50 km distance from the sensors. The geolocation error dependency on different parameters was also investigated. The geolocation error was found to be proportional to the error in the measured parameter, proportional to the inverse of the distance between the sensors, proportional to the inverse of the trajectory length and proportional to the inverse of the square root of the number of measurements. Further, the simulations showed that the geolocation error increases rapidly with increasing distance from the sensors. Additional factors that may affect the geolocation accuracy, but that have not been included in our calcuations, are errors in the reported sensor position, emitter movement during the observation period and limitations in de-interleaving capability and data transfer capacity. Recommendations for geometry and trajectory choices for the sensors are included in the report.