The precise location of an ingested radio transmitter/sensor is of importance in gastroenterology studies. Given the complex geometry of the gut and the very large variations in human size and electromagnetic characteristics, inverse modelling from surface based measurements is very complex and a unique location solution is not possible. This paper proposes a simple method based on far-field approximation of the attenuated field from the ingested transmitter. The validation experiments for an ellipsoid cylinder using averaged electromagnetic properties of the human GI tract (conductivity 0.87 S/m, relative permittivity 62) and a Hertzian dipole radiator inside the body with a frequency of 433 MHz were conducted assuming a receiver dynamic range of less than 100 dB. The reliability of the method was verified by comparison with FDTD modelling. The method provides an analytical solution to estimate the surface field intensity depending on the dipole location and orientation with a negligible computational cost. This efficient algorithm can be incorporated into an inversion algorithm for localization of wireless endoscopy sensors to allow precise targeted treatment.