Geology Reference
In-Depth Information
Figure 1.17
Multiple systems mounted on a purpose-built wooden sledge.
1.7.3 Towed systems
Putting a sensor on a survey vehicle is undesirable if the vehicle is likely
to be a source of noise. It may also be difficult to mount all the equipment
needed for a multi-system survey on the vehicle and still leave room for
the driver. Towing the instruments behind the vehicle on a purpose-built
sledge then becomes a better option. The towed system in Figure 1.17 was
used to record combined ground conductivity, natural gamma and multiple
total field magnetometer data to simultaneously map shallow geological
deposits, cross-cutting pipelines, archaeological features and buried pits
along a proposed linear route. A DGPS system with EGNOS availability
(see Section 15.2) was used to record locations to approximately 2-m spatial
accuracy.
Multi-instrument platforms in their most advanced form have been de-
veloped in the USA to improve the efficiency of scanning firing ranges and
battlefields with multiple magnetometers and time domain EM systems syn-
chronised so that they do not affect each other. The systems utilise not only
real-time GPS control but are integrated with inertial navigation units to
provide accurate dead reckoning navigation in the event of poor GPS signal.
These platforms offer huge cost savings compared with separate surveys or
