Case Study
Sample Density and Resolution
Geophysical sampling is typically performed by
recording data values at regular intervals along parallel
transects across the survey area. The sample density, sometimes
expressed in samples per square meter, determines the effective
resolution of the survey as well as the rate of coverage.
Sample density is therefore a compromise between cost and
the likelihood of resolving anticipated features of interest.
No meaningful consideration of survey design or budget can
occur without considering sample density. Although appropriate
sample densities differ between each instrument, the sample
interval should be proportional to the scale and contrast
of anticipated features. Appropriate transect intervals typically
range from 0.25 to 1 meter, with multiple readings per linear
meter along each transect. Occasionally, greater sampling
intervals may be appropriate to identify general areas of
activity or occupation, although it is impossible to map typical
individual features.
Two case studies (right) graphically illustrate
how sample density affects resolution of resistance and magnetic
surveys.
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Resistance Survey
Cahokia Mounds
Magnetic Survey
3030
Winchester
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