G-858BP Backpack Mag Operators Manual
Appendix 1: Surveying Principles
This section outlines the principles of performing a magnetic survey for anomaly location. It
covers setting up, performing the survey and location of items of interest within the anomalous zones.
Regional or geologic surveys for mineral exploration require a different set of procedures and are not
covered in this overview. However, many of the guiding principles are identical and review of this section
will be helpful.
Guidelines for Small Ground Magnetometer Surveys
The general comments below cover only the site layout and preparations for a survey. The survey
objectives, determination of parameters for the instrument data collection and the actual data processing
and map preparation are covered elsewhere.
In order to accomplish a successful ground survey magnetometer data acquisition, survey path
over the ground and processing of the data into map form must be handled in a precise and accurate
manner. Each element is completely interdependent upon the others and if one is compromised in quality
or accuracy then all are compromised. During a survey, possibilities for error are numerous and great care
and concentration are required to avoid mistakes, some of which may be so serious as to require starting the
survey over. The focus should be on completing the survey completely error-free.
Typically, the most difficult surveys are those involving detection of small magnetic targets and
the presentation of an accurate 1 or 2 nT contour map. In these cases, the survey must include: a close line
spacing (1-2 m) with precise tracking in both the X- and Y- directions; diurnal correction (0.5 nT or better);
correction of heading errors from instrument and/or operator; maintaining the sensor a constant distance
above the ground; and absolutely no mistakes in procedure and data processing.
Number of People
Under certain conditions, the survey can be laid out and run by one individual; but this is rare and
risky. It is far better to have a minimum of two people closely involved and ideally, three or even four
people. Not only must the layout and marking of the survey lines be considered but also an individual must
be designated to maintain a separate survey log, set up the base station, and operate the portable
magnetometer. Note also that the operator doing all of the walking may require relief, for oftentimes the
terrain and distance conspire to make his job very grueling.
Survey Efficiency
Speed and cost-efficiency in completing the survey is of course the ideal objective. This does not,
however, require the use of innovative short cuts, new gadgetry or excessive manpower, but rather the
avoidance of mistakes and errors. To prevent wondering off line even once in the course of a survey, with
all of the attendant time spent sorting out and making the corrections, easily justifies a slower but more
positive method. Efficiency will only be achieved by avoiding confusion, the correction of errors, and by
the use of fail-safe procedures. All of the methods suggested below are simple low tech, and relatively
slow, but proven effective. They can easily be improved upon but only at the risk of greater time, survey
quality, or greater cost. So in the beginning, keep it as simple as possible.
Layout of the Survey Track
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