Abstract: A method of measuring the power of a signal from a transmitter (10) causing interference with a receiver (16) involves geolocating the transmitter (10) via satellites (24) and (28) or aircraft A1and A2. The receiver (16) is part of a satellite-implemented Global Navigation Satellite System. Geolocation involves finding a correlation peak between replicas of the transmitter's signal to determine their differential time and frequency offsets, from which a transmitter's location is calculated. The transmitter's signal power P1 is a solution to a quadratic equation with coefficients involving the transmitter's distances D1 and D2 from the satellites (24) and (28), its transmit wavelength ?, total noise temperature TN of each satellite's receiver system and antenna, correlation peak signal to noise ratio SNRc satellites' receive antenna gain Gs sample bandwidth B at outputs of the satellite receivers' ADCs and correlation integration time T.