Abstract: Helmet trackers include transmitters to transmit information regarding the orientation and position of the helmet, receivers to receive the information, and processors to process the information to determine the position and orientation of the helmet. An apparatus, connected to the transmitter, is used to attain a faster response time for the transmitter to transmit. Such apparatus may include an amplifier, a plurality of capacitors connected to the amplifier, a plurality of transistors each connected to a respective capacitor, and a controller connected to each transistor to control when a transistor turns on. The capacitors can store charge while the transistors are “off,” and once the transistors are turned “on”, an instant charge will exist to supply energy to the transmitter.

Abstract: Resistivity mapping apparatus includes a tow mechanism for use by a human operator in moving the mapping apparatus over a surface and measuring the resistivity of soils of the surface. The tow mechanism includes a generally triangular shaped tow ring which is engageable by the operator's battery belt, harness, or pack-frame, the tow ring having two opposing hooks at a vertex of the tow ring for receiving a loop from a tow line. The tow line engages the tow ring and a cable depressor weight which keeps the resistivity mapping apparatus in close proximity to the earth as the apparatus is towed. A communication cable in the tow line preferably comprises an optical fiber which transmits signals from the receiver to a data logger carried by the operator.