To establish if the measurement poles, that are stabbed in the seawall through 60cm thick asphalt/tarmac layer, really show what is going on below the asphalt layer, we have mounted a reference sensor to the asphalt directly next to the most eastern (pole-)sensor (number 7)
In the animation shown below., you see a scaled wire-model of the situation. The wire-box represents a 2 x 2 meter and 60cm thick chunk of asphalt. The measurement-pole in the middle anchors 180cm deep below the asphalt in the sand-layer.
The animation shows the real movements measured by the sensores between 24-10-2012 17:30 en 19-10-2012 10:25 and is amplified 1000 times.