Specifications

University of Pretoria etd – Combrinck, M (2006)
Chapter 5
5 APPLICATION TO FIELD DATA
"The bitterness of low quality remains long after the sweetness of low price is long forgotten.”
(Benjamin Franklin, 1706-1790)
5.1 Introduction
This chapter contains results of S-layer differential transform applied to two data sets,
one from a ground survey and one from an airborne survey. The ground survey covers
an area of roughly 2km by 6km at low resolution (50m or 100m station spacing) with the
intent to identify locations of conductors for follow-up work. The airborne data consists
of a very high resolution (3m station spacing on average) line over an easily recognizable
conductor and the purpose is to determine the depth and orientation of this body. Both
survey geometries conformed to the central loop sounding configuration.
5.2 Ground survey
5.2.1 Data acquisition and system parameters
The data used were acquired in a sedimentary environment which has undergone various
metamorphic events resulting in complex structural features. A TDEM in-loop survey
was done across a mountain (Figure 5-1). The data acquisition was done under extreme
field conditions. The station- and line-spacing varied across the survey area (mostly 100m
line- and 50m station spacing). The grid that was surveyed is given in Figure 5-2. A total
of 1543 stations were surveyed. At each station both the high and medium frequencies
were utilized on the transmitter. The survey was done using a GEONICS EM57
transmitter and PROTEM receiver with a single component receiver coil. Parameters
used for the survey are:
Frequency
: 25 and 6.25Hz
Transmitter Loop Area: Single Turn 100x100m
Transmitter current: 14.5 A
100