A network of radio detection and bearing units can be a powerful tool to prevent radio communication for the poachers. The point is, even with only a few units, all GSM phones inside and outside the sanctuary can be detected and located. A larger frequency band can be scanned, to also find other communication devices.
A detected cell phone can easily be associated with an intruder. First, the ranger positions are known to the system, so these cell phones can be eliminated. Second, during night time, the whole Tsavo park is closed for visitors. During daytime, visitors are only allowed in vehicles on the road network. Further, when visiting Ngulia 4--6 pm, they need to checkin at the gate, and can after this be followed during their visit. All cellphone positions that do not correspond to any of the conditions above are thus very
The video below shows an experiment with localization of a cell phone by measuring the received signal strength from a drone. The left picture shows a snapshot image from the drone, while the right picture shows the operator view, where the measurement positions are marked with yellow, and the estimated position after each measurement is illustrated with red. The true position is also marked here for reference.