1. A method for determining a geolocation of a non-cooperative target, the method comprising: a) acquiring with at least one collector one or more actual signal measurements corresponding to a signal emitted from an emitter on the target, wherein the one or more signal measurements include at least one of a direction of arrival, a target range, a time difference of arrival, a range rate, a range sum, and a frequency difference of arrival; b) receiving with a processing device the actual signal measurements and navigational data regarding the collector; c) calculating an estimated target location of the non-cooperative target with the processing device as a solution to a non-linear optimization problem using a globally convergent optimization algorithm, wherein an objective function to be minimized is a weighted sum-of-squares of differences between the actual signal measurements and calculated values corresponding to signal measurements that theoretically should be produced for a particular target location; and d) outputting the estimated target location to a display configured to display the estimated target location or to another electronic device.