Archaeo-Physics, LLC - geophysical survey and subsurface mapping

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.

 

 

Cahokia mounds resistance / resistivity survey
Resistance Survey
Cahokia Mounds

magnetic survey at 3030 Winchester
Magnetic Survey
3030 Winchester

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