Predictions of bird swing from GPS coordinates

Abstract

Bird attitudes, with roll, pitch, and yaw angles, are required for modeling the measured electromagnetic response of the earth. Global Positioning System (GPS) antennas can be used in airborne electromagnetic (AEM) systems to monitor airborne platform attitude and bird maneuver. We have found evidence from photographic sequences that four GPS antennas, three on the bird and one on the aircraft, generally are adequate for angular and altitude geometry control. The mounting system for the bird frame introduces vibration noise. We have developed a model that predicts bird maneuver from the use of GPS antennas already present during routine airborne surveys. The bird motion, whether inline or crossline, is modeled from the difference between the aircraft location and the mean location of the bird. This also accurately predicts the roll of the bird when an inline yoke mounting is used. The minimum number of GPS antennas required to monitor the motion of a cylindrical electromagnetic (EM) bird typical of frequency-domain systems is two, one on the aircraft and one on the bird. We have defined optimum locations of GPS antennas to enable geometric monitoring of towed-bird systems. The findings suggest that the bird be mounted with two aerodynamically efficient GPS antennas, one on the nose and one on the tail. This enables the measurement of the pitch and yaw of the bird, with roll deduced using the third GPS on the helicopter.

Bathymetry and Its Applications

“…However pendulum motion of the towed bird generates a geometric and inductive effect in the measured EM response and contributes to altimeter error (Davis et al, 2006). If the bird swing period can be determined from survey data, a filter can be designed to remove bird swing effects, to first order, caused by pendulum motion (Davis et al, 2009). Predictions of bird swing from GPS receivers mounted on the bird and the helicopter can be used to predict the bird maneuver (Davis et al, 2009;Kratzer & Vrbancich, 2007).…”

“…If the bird swing period can be determined from survey data, a filter can be designed to remove bird swing effects, to first order, caused by pendulum motion (Davis et al, 2009). Predictions of bird swing from GPS receivers mounted on the bird and the helicopter can be used to predict the bird maneuver (Davis et al, 2009;Kratzer & Vrbancich, 2007). Calibration errors in FEM helicopter data can be identified by transforming the data to several different response-parameter domains and used to minimise the effect of altimeter and bird maneuver errors (Ley-Cooper et al, 2006).…”

On the value of including x-component data in 1D modeling of electromagnetic data from helicopterborne time domain systems in horizontally layered environments

“…Rotation of receivers will cause a projection of field components into each receiver coil, effectively making each coil measure a superposition of the X-, Y-and Z-components. Since such geometric effects can be substantial it is desirable to have highly accurate measures of pitch, roll and yaw, which can require sophisticated monitoring and processing methodology (Davis et al, 2009). Assuming accurate geometric information is available it can be accounted for in different manners.…”

Airborne Electromagnetic Bathymetry

“…However pendulum motion of the towed bird generates a geometric and inductive effect in the measured EM response and contributes to altimeter error (Davis et al, 2006). If the bird swing period can be determined from survey data, a filter can be desig ned to remove bird swing effects, to first order, caused by pendulum motion (Davis et al, 2009). Predictions of bird swing from GPS receivers mounted on the bird and the helicopter can be used to predict the bird maneuver (Davis et al, 2009;Kratzer & Vrbancich, 2007).…”

“…If the bird swing period can be determined from survey data, a filter can be desig ned to remove bird swing effects, to first order, caused by pendulum motion (Davis et al, 2009). Predictions of bird swing from GPS receivers mounted on the bird and the helicopter can be used to predict the bird maneuver (Davis et al, 2009;Kratzer & Vrbancich, 2007). Calibration errors in FEM helicopter data can be identified by transforming the data to several different response-parameter domains and used to minimise the effect of altimeter and bird maneuver errors (Ley-Cooper et al, 2006).…”