Time-domain electromagnetic systems are most sensitive to highly conductive targets during the transmitter on-time. Data collected during the on-time is highly influenced by the geometric relationship between the transmitter and the receiver. Unless corrections can be applied for these geometric variations, the ability to correctly detect and identify highly conductive targets can not be fully realized. Variables affecting the relative position between the transmitter and receiver include changes in the position of the receiver with respect to the transmitter, variations in transmitter attitude, and transmitter loop deformation. The level of accuracy in the determination of the relative geometry required to permit complete removal of the effects due to geometric variations is different for each of the variables and is dependent on the depth of the target. The most influential geometric variation involves changes in the relative position of the receiver with respect to the transmitter along the direction of flight; this variable, therefore, requires the highest degree of accuracy. The accuracy required for receiver motions along the vertical direction is roughly one order of magnitude less, and in the lateral direction, several orders of magnitude less. The objective of this paper is to relate the sensitivity of the response to transmitter-receiver geometry to the ability of an airborne, time-domain electromagnetic system to resolve a highly conductive vertical target. This is achieved by a detailed analysis of the effect of the individual x, y, and z distances between the transmitter and the receiver, the transmitter attitude (roll, pitch, and yaw), and transmitter deformation.

A technique to improve the positional accuracy of mobile ground-based LIDAR systems is proposed. Terrapoint's TITAN TM system scans the same objects at different times, so by aligning scans, any drift over time can be estimated. This paper describes a simple way of tessellating the scanned data into segments based on the vehicle's path. Principal Components Analysis is then used to estimate how well pairs of segments will align when registered with an Iterative Closest Point algorithm. The results show that this analysis does indeed find segments which are likely to register well. Finally a more formal method to analyze the results is proposed, to better determine the quality of the registration so that it can be used to improve the position estimate for the LIDAR system.Canadian Conference on Computer and Robot Vision 978-0-7695-3153-3/08 $25.00

The Gedex High-Definition Airborne Gravity Gradiometer (HD-AGG™) was designed and developed to deliver measurements of the gravitational field with improved signal-to-noise and resolution. The system has been under development for more than 10 years and has reached the point of commercial deployment. Knowledge of the gradiometer components being measured, noise character and resolution of the system will allow end-users to select exploration targets and determine survey parameters appropriately. The validation of the Gedex system has been progressive in nature consisting of laboratory tests and flight tests in a Cessna Caravan. The lab experiments consisted of static tests to establish the quiescent noise floor, signal confirmation tests and dynamic testing on a 6 degree-of-freedom shaker. The airborne testing included high altitude flights to confirm the noise level and character of the system over long periods. Low-level repeat surveys were carried out to establish the noise levels under survey conditions. High resolution terrain data were used to confirm the resolution of the system. Datasets from our validation program and the path forward are discussed.

Quantifying the effects o f transmitter-receiver geometry variations on the capabilities of airborne electromagnetic survey systems to detect targets of high conductance

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