BARTINGTON INSTRUMENTS
Page 54 of 61 OM1800/26
Appendix: Practical Aspects of Surveying
This section describes practical aspects of setting up and using the Grad601 single and dual
sensor gradiometers for archaeological prospecting, and for detailed mapping of archaeological
features.
Note:
Some points, which have been covered in the earlier text, are repeated where it may
be appropriate.
Note:
For the more technical aspects of surveying, see
Survey Mode (Grid Mode)
and
Survey Operation (Grid Mode)
.
A.1. Conventions
For compatibility with existing plotting software and current practice, certain conventions apply.
•
The site to be surveyed will be divided into areas (Grids) of 10x10, 20x20, 30x30 or 40x40m
over which data is collected for subsequent assembly into a matrix.
•
The gradiometer is carried along a series of traverses across each Grid. The first traverse
may start at any corner of the Grid, but the operator must set off in a clockwise direction as
shown in
Figure 12
. This enables the data to be plotted with the correct orientation, using
only the starting direction from the list of parameters saved as a header file.
•
Plotting software will normally show a single Grid with the first traverse starting from the top
left corner as shown in
Figure 13
.
•
Traverses may be done with a parallel or zigzag pattern as shown in
Figure 10
and
Figure 11
,
respectively.
•
If a 10x10m Grid is constructed from 1m squares, and measurements are to be made at 1m
intervals along 1m traverse intervals, then make measurements at the centre of each Grid
square as shown in
Figure 14
. This allows the data from adjacent Grids to be seamlessly
joined, and no convention is required about which edges are used for reference.
•
The same principle applies when the sampling interval is less than 1m. For a sampling
interval of 0.25m, the first reading will be taken at 0.125m from the start of each traverse and
the last at 0.125m before the end of each traverse.
A.2. Planning the Survey
•
It is important to remember the position of each Grid, and any reference points, to be able
to assemble the individual Grids later into a matrix showing the complete site. Keep careful
notes when planning the site survey.
