Abstract: A survey system for acquiring survey data representative of a subterranean structure includes a plurality of sensor modules. Each of at least some of the plurality of sensor modules includes a wireless transceiver to communicate wireless signals with another component in the survey system, and a plurality of parts. A first of the plurality of parts is detachably attached to a second of the plurality of parts, with the first part including a sensor, and the second part including a power source and a non-volatile storage.

Abstract: To control activation of one or more communication units in a survey system that performs surveying of a subterranean structure, optical activity on at least one optical link connected to at least one communication unit that is part of a survey system is detected. In response to determining that the optical activity has a characteristic that satisfies a predetermined criterion, the at least one communication unit is awakened.

Abstract: A method and apparatus for synchronizing a real time clock of a slave computer with a real time clock of a master computer. The method includes the steps of: calculating a first time drift value between the real time clock of the slave computer and the real time clock of the master computer, calculating a second time drift value between the real time clock of the slave computer and the real time clock of the master computer, calculating an average time drift value between the real time clock of the slave computer and the real time clock of the master computer using the first time drift value and the second time drift value, and adjusting the real time clock of the slave computer using the average time drift value.