Geoscience Reference
In-Depth Information
21
Mapping Golf-Course
Features with Electromagnetic
Induction, with Examples
from Dublin, Ohio
Richard S. Taylor
ContentS
21.1 Introduction ......................................................................................................................... 287
21.2 Apparent Conductivity by EMI........................................................................................... 287
21.3 Resolution of Measurement................................................................................................. 288
21.4 Golf-Course Green Model .................................................................................................. 289
21.5 Survey Examples................................................................................................................. 290
21.6 Conclusions ......................................................................................................................... 292
21.7 Acknowledgments ............................................................................................................... 294
References ...................................................................................................................................... 294
21.1 IntRodUCtIon
Electromagnetic induction (EMI) is a convenient technique for mapping apparent electrical conduc-
tivity over large areas and varied terrain. In recent years, the resolution of EMI instrumentation has
improved such that the technique can enable the detailed analysis of spatial and temporal changes
in conductivity. High-resolution EMI surveys are suitable for mapping features of the scale typical
of golf-course greens and tees. Such surveys can check the depth and extent of the materials used
to construct golf-course features, and may be of some use in monitoring the response of features to
environmental fluctuations and managerial practices.
This note briefly reviews the measurement of apparent electrical conductivity by EMI, com-
pares the resolution of an available instrument to that required for mapping features at golf courses,
and presents several examples from test surveys in Dublin, Ohio.
21.2 AppARent CondUCtIvIty by eMI
An electromagnetic (EM) array of a transmitter and receiver provides the standard means of mea-
suring apparent conductivity by EMI. The EM array is defined by the separation between the trans-
mitter and receiver and the relative orientation of these components. The most popular arrays for
measuring apparent conductivity have less than 5 m separation, and their orientations are termed
horizontal coplanar (HCP) and perpendicular (PRP).
The apparent electrical conductivity measured by EMI at some height above a layered earth is
influenced by the thickness of the “air layer” between the EM array and the earth, and the thickness
287
