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This is two different views (3D and 2D) of the same results of a differential PPM survey made over a roman site (vicus) located in Belgium.
The grid is made of 1x1 meter cells and has only taken around one hour to be captured.
The underground structure seen at 15,15 of the grid was a large (5x5 meters) roman cellar made of well-conserved stone walls. We already knew from the archives that a cellar was on that particular large cultivated field but forgot where it was exactly.
The two narrow shapes seen at 30,17 and 42,15 are typical of long iron objects (magnetic dipoles). Indeed, they were modern parts of agricultural machines (two long pieces of iron) found at a depth of around 50cm.
These survey results proved that our PPM system was sensitive enough to detect underground structures made of stones or bricks with a survey speed high enough to cover large area in reasonable time and effort unlike the ground resistivity methods.
The differential PPM system was a system designed and built by a small team of retired engineers (Jim Koehler, Paul Cordes, Willy Bayot).
The system is made of two PPM devices, one static station used to compensate for the diurnal field variations and one mobile station carried by a walking operator (myself).
At the time of the survey, the grid was still defined on the ground the hard way (with decameters and survey lines) but, in the meantime, we have equipped the system with a GPS to define the absolute coordinates of each point. Our current experience (and still short) with this GPS-controlled grid is very satisfactory getting a precision of around a meter. This was a good surprise but can be explained by the fact that the surveyed field has a full sky view and we usually get 10 to 12 satellites in view giving a very good horizontal precision.
These results gave us the motivation to continue to improve our PPM system in order to reduce its power consumption and sensor weight while still keeping the same sensitivity and accuracy. This will certainly be a welcome instrument for our future archeaological work.
The grid is made of 1x1 meter cells and has only taken around one hour to be captured.
The underground structure seen at 15,15 of the grid was a large (5x5 meters) roman cellar made of well-conserved stone walls. We already knew from the archives that a cellar was on that particular large cultivated field but forgot where it was exactly.
The two narrow shapes seen at 30,17 and 42,15 are typical of long iron objects (magnetic dipoles). Indeed, they were modern parts of agricultural machines (two long pieces of iron) found at a depth of around 50cm.
These survey results proved that our PPM system was sensitive enough to detect underground structures made of stones or bricks with a survey speed high enough to cover large area in reasonable time and effort unlike the ground resistivity methods.
The differential PPM system was a system designed and built by a small team of retired engineers (Jim Koehler, Paul Cordes, Willy Bayot).
The system is made of two PPM devices, one static station used to compensate for the diurnal field variations and one mobile station carried by a walking operator (myself).
At the time of the survey, the grid was still defined on the ground the hard way (with decameters and survey lines) but, in the meantime, we have equipped the system with a GPS to define the absolute coordinates of each point. Our current experience (and still short) with this GPS-controlled grid is very satisfactory getting a precision of around a meter. This was a good surprise but can be explained by the fact that the surveyed field has a full sky view and we usually get 10 to 12 satellites in view giving a very good horizontal precision.
These results gave us the motivation to continue to improve our PPM system in order to reduce its power consumption and sensor weight while still keeping the same sensitivity and accuracy. This will certainly be a welcome instrument for our future archeaological work.