13th June 2008, 09:57 PM
As a geophysicist I can confirm that there is no way that geophysical surveys can be expected to provide a complete picture of the archaeology of pipeline corridors. I have been involved in two such surveys of late, and whilst both proved valuable in detecting archaeology, neither was entirely effective and in neither case do I believe that the 'blank' areas will necessarily prove to be blank.
Apart from the usual caveats with geophysics (it doesn't work well on all geologies, can't 'see' much below alluvium, colluvium or made ground and struggles to detect post-holes, burials etc), there is a particular difficulty with linear projects. Interpretation is usually based on the plan view of sites and thus it becomes much more difficult when only a narrow (c20-40m) strip of data is available.
Another problem with pipeline corridors is that they often follow the route of previous pipes, and so there will be streches of the data where any archaeological anomalies which may occur are swamped by the massive magnetic halos from these pre-existing pipes.
Apart from the above considerations, it would be unsual for a geophysical survey to cover the entirity of a pipeline route. Woodland, waist high rape crops, over attentive livestock, shotgun waving gamekeepers and so forth have a habit of getting in the way. It also seems par for the course that the route you're sent to survey will differ in stretches from the one which the pipeline actually ends up following.
I'm not saying that geophysics on pipeline corridors is a waste of time. It can, and does, provide valuable results. Its just that one should be very wary of placing too much weight on survey results alone.
John
"Hidden wisdom and buried treasure, what use is there in either?" (Ecclesiasticus ch20 v30)
Apart from the usual caveats with geophysics (it doesn't work well on all geologies, can't 'see' much below alluvium, colluvium or made ground and struggles to detect post-holes, burials etc), there is a particular difficulty with linear projects. Interpretation is usually based on the plan view of sites and thus it becomes much more difficult when only a narrow (c20-40m) strip of data is available.
Another problem with pipeline corridors is that they often follow the route of previous pipes, and so there will be streches of the data where any archaeological anomalies which may occur are swamped by the massive magnetic halos from these pre-existing pipes.
Apart from the above considerations, it would be unsual for a geophysical survey to cover the entirity of a pipeline route. Woodland, waist high rape crops, over attentive livestock, shotgun waving gamekeepers and so forth have a habit of getting in the way. It also seems par for the course that the route you're sent to survey will differ in stretches from the one which the pipeline actually ends up following.
I'm not saying that geophysics on pipeline corridors is a waste of time. It can, and does, provide valuable results. Its just that one should be very wary of placing too much weight on survey results alone.
John
"Hidden wisdom and buried treasure, what use is there in either?" (Ecclesiasticus ch20 v30)