Grids, Lines And Positions; Survey Methods; Equipment Required - Bartington Grad601 Operation Manual

A.4. Grids, Lines and Positions
• Each Grid is normally surveyed with a line interval of 1m, and a sample interval of 0.25m
along the line of the traverse. This is a good compromise between the sampling rate and
walking distance, and provides good resolution of archaeological features. The Grad601 may
be set for line intervals of 0.25m, 0.5m or 1m and sampling intervals of 0.125m, 0.25m, 0.5m
or 1m.
• The Grad601 saves Grids in numerical order starting with Grid 1. The memory has sufficient
capacity to store the equivalent of 36 Grids of 30x30m with 1m line spacing and 4 readings
per metre.
• For the Grad601-1 single sensor gradiometer, the traverse lines correspond to the data lines.
For the Grad601-2 dual sensor gradiometer, the number of traverses will be half the number
of data lines. The data logger allocates numbers to the traverse lines starting with 1.
• The positions at which samples are taken along each traverse line are also numbered,
starting at position 1. The current position is displayed during the survey.
A.5. Survey Methods
The survey method will depend on the purpose of the survey. For archaeological prospecting
prior to land development, the operation may need to be carried out quickly and with the
minimum number of personnel. Detailed surveys of archaeological sites may require more
precise measurements and additional personnel may be available.
Note: The following suggestions assume data is required at 1m traverse intervals over a
30x30m Grid with a zigzag pattern, and are recommended for most purposes as a starting
point. For line spacing of 0.5m or 0.25m, refer to
equipment.
A.6. Equipment Required
Note: All equipment used must be non-magnetic. Mark about 12 bamboo canes of about
1m in length with fluorescent markers so they are easily seen from a distance.
Assuming a survey of a 30x30m Grid at 1 line/m, prepare a trapeze with two rigid bars just
over 1m wide joined by two 30m ropes spaced exactly 1m apart. Mark the trapeze ropes at 1m
intervals with the first mark at 1m from the end bar. Mark the supports at the centre between
the two ropes.
To mark the start and finish of the traverses, prepare two 30m ropes with loops at the ends to fit
over canes when pushed into the ground 30m apart. Mark these ropes with fluorescent sleeves
or tape to show the start and end of each traverse.
BARTINGTON INSTRUMENTS
Figures 17 to 21
Page 56 of 61
to prepare the survey
OM1800/26