Triaxial Gradiometer System

Introduction

Fugro Airborne Surveys has developed the world's first three-component, four- sensor, magnetic gradiometry platform. Diamond explorers favour gradiometry data to correctly position kimberlite pipes on the ground. Mineral exploration companies and government surveys acquire more detailed information with a gradiometer than a single sensor using similar survey specifications.

Cessna 208 Caravan - TRIAX System
(Note the horizontally & vertically separated sensors on wingtips and tail respectively)

The system comprises two vertical tail sensors and two horizontal wing-tip sensors separated by 2 and 16 metres respectively (see above). This configuration allows Fugro Airborne Surveys to observe three components of the earth's magnetic field in real time. Two advantages of acquiring gradiometry data are:

1. Resultant Horizontal Gradient Gridding Enhancement
2. Anomalous Magnetic Field Derivation

Resultant Horizontal Gradient Gridding Enhancement

Resultant horizontal gradient vectors derived from both the longitudinal and transverse gradients improve interpolation between lines. 

Direct results of the application of Horizontal Gradient Enhanced (HGE) gridding are:

• Increased resolution of parallel to sub parallel magnetic features. 
• Correct spatial positioning of finite source magnetic bodies between lines.
• Improved resolution of analytical signal products.

Anomalous Magnetic Field Derivation

Fugro Airborne Surveys can demonstrate that observed gradients are impervious to diurnal magnetic field effects, being instantaneous observations over short base lines. The resulting Anomalous Magnetic Field Derivation (AMF) is therefore devoid of diurnal field effects. Due to the frequency of the gradients and inherent limitation of the sensitivity of the magnetometer, long wavelength magnetic features are lost. 

The AMF is derived by:

• Derivation of the vertical gradient from observed horizontal and longitudinal gradients using La Place's equation or the direct employment of the observed vertical gradient.
• Integration of the vertical gradient in the frequency domain.