Geolocalization by combined range difference and range rate difference measurements

The paper derives a geolocation estimator from range difference and range rate difference measurements collected by orbiting satellites. When the emitter is known to be located on the the Earth´s surface, the accuracy in locating the emitter´s position is improved by constraining the position estimate. An important factor associated with the constrained problem is the selection of an appropriate model of the Earth. As opposed to a spherical model, which introduces latitude dependent bias, the oblate spheroid closely resembles the Earth. Quadratic constraints formed from an oblate spheroid model of the Earth are applied in constraining the geolocation solution