WARRANTIES AND LIMITATIONS
The material means used during the pyrotechnic diagnosis are geophysical tools whose primary purpose has been diverted to identify any anomalies present in the subsoil and likely to be similar to unexploded pyrotechnic devices or explosive remnants of war. .
They are not ammo detectors.
As a result, these detectors are subject to the various limitations of these methodologies.
In this case, it is difficult to define the precise size of an object (or its weight or its volume) or its depth with certainty.
Magnetometry :
Magnetometry is highly sensitive to all surface effects, including ferromagnetic superstructures of all types (buildings, fences, machinery, cars, etc.). The presence of these types of objects on the surface does not allow measurements to be taken up to several meters from them.
The more the ground is polluted by ferromagnetic objects, the more the individualization of the anomalies is difficult and the more the technical and depth characteristics of the object are difficult to identify.
Map display scales or data processing thresholds are essential for defining the types of ammunition to be identified according to their depths.
In general, the smaller the ammunition, the less it is detectable in depth.
Fluxgate magnetometry allows the identification of bombs from 250 to 500 kg up to a maximum depth of 3 or 4 m under optimal surface and ground conditions.
The magnetometry total fields » allows to investigate the subsoil slightly deeper (about 30% more) but is at the same time much more influenced by the superstructures.
Depending on the means used (single or multi-antenna, georeferenced in real time or by post-processing) and the terrain to be investigated (flat or uneven, open or not, presence of a structure or not, passable on foot or by vehicle, small or large), the magnetometric diagnosis can cover between 2500 m² and 10 hectares per team and per day or even more for airborne means.
Electromagnetism (TDEM) :
TDEMs intended for the search for unexploded ordnance have search depths between 2 and 3 m maximum for the largest objects.
They remain influenced by superstructures but to a lesser extent than magnetometry.
The classification of anomalies by category and the burial depths are more precise thanks to the different measurement windows compared to magnetometry.
As with magnetometry, map display scales or data processing thresholds are essential for defining the types of ammunition to be identified according to their depths.
Following the same constraints as for magnetometry, the TDEM diagnosis can cover between 2500 m² and 2 hectares per team and per day.
It should be noted that this method allows the detection of ferrous and non-ferrous objects. This method is therefore essential in the context of diagnosis of modern firing ranges on which magnetometric measurements would not be effective.
Electromagnetism (Gear box) :
The georadar measures the zones of dielectric changes. That is to say, it is extremely constrained by the consistency of the subsoil and in this case by the different layers that make it up.
The presence of an area of fill or water in the surface layers does not allow for deeper investigations.
The ground penetrating radar does not clearly distinguish between a ferrous, non-ferrous or geological anomaly.
It allows, unlike other methods, to investigate areas close to superstructures thanks to these shielded antennas.
The choice of shielded antennas is also essential because it allows the investigation more or less in depth and with more or less precision of the subsoil.
Following the same constraints as for magnetometry and TDEM, georadar diagnosis can cover between 2500 m² and 5000 m² per team and per day.
