At first glance and without modelling, I would suggest that your objects are too large to be placed so close together. For mag dipoles, the rule of thumb is that the half width equals the depth. I would make each cell at least 15x15m with one object in each. For the data you have, look for overlapping signatures rather than discrete objects.
-Jeff
At 10:08 AM 4/6/00 , you wrote:
L.S.
In the Netherlands a test site of 15m X 15m a 10 kg drum, 250 kg pipe, 125 pipe, 25kg H-bar and a 25 kg chain were buried at various depth. The max depth was about 5 meter.
The survey was conducted with a line spacing of 1 meter in the North direction. We used a 858 Geometrics gradiometer which measured the vertical gradient (sensor delta distance of 1m).
Using the UXO module from Oasis the computer generated various grids; total field of both sensors, average total field, vertical gradient and the analytical signals of both the sensors and the analytical signal of the gradient.
The results were dissapointing. Though finding alot of objects, this survey failed to find the objects we buried. Except for the 25 kg H-bar.
What happend?
Is there anybody who is facing the same problems?
Could near surface objects distore the measurements in such a way that our kown objects were unvisable?
Can anybody model (calculate) the magnetic field lines of objects in the magnetic field.
What kind of readings should I expect on a survey like this? Total field value for quit region is 48400 nT.
I know a lot could be wrong or go wrong, but has anyone experience in detecting such objects ?.
Best regards,
Joep Grooten
GeoCom The Netherlands.
P.S. A EM61 survey was also done (afterwards) which yielded the same results.
*******************
* Jeff Gamey (4tj)
* Environmental Sciences Division
* Oak Ridge National Laboratory
* [EMAIL PROTECTED]
* (865) 574-6316 tel
* (865) 576-8646 fax
