NL8007110A - Magnetic position markers - placed in plastic sheet and buried in ground in place of boundary markers - Google Patents

Abstract

Conventional methods of marking land boundaries usually suffer from the following disadvantages, they are intrusive in areas of natural beauty, liable to vandalism and erosion, expensive to install and, over many years, can become lost in undergrowth or shifting topsoil. It is suggested to use high power permanent magnets buried at a depth of 1.5 to 2.5 metres. Permanent magnets hold their magnetic properties for many hundreds of years and can be easily detected using gradient-magnetometers, using the flux gate principle . They can be installed in a protective plastic sheath by drilling a hole in the ground and dropping them in. If several magnets are buried in close proximity, they can be of differing strengths, thus enabling easy identification.

Description

'y & ~ ~ - 1 -

Institute for Soil Mechanics and Foundation Technology. Wilhelminasingel, 29,

Maastricht.

Short designation: Magnetic exploration points.

The present invention concerns the provision of landmarks and the retrieval of these landmarks. The invention hereby provides for the implementation of these landmarks in the form of strong permanent magnets and the retrieval and detection of these magnets using a magneto-10 meter, preferably a gradient magnetometer, of the fluxgate principle.

In the current state of the art, sites on grounds or buildings are marked by exploration points, sometimes the precision of marking is of great importance, sometimes the resistance of the applied exploration point. In many cases, this landmark is accessible to everyone and usually clearly visible. However, when such an exploration point has been in an unmanaged state for a very long time, it cannot be excluded that the exploration point will be disturbed by unauthorized persons. Apart from a very expensive solution of very heavy concrete structures, no solution of this problem is known in the prior art as described in the present embodiment. The present invention has the advantage that the reconnaissance point is not only difficult to reach or access, but is also invisible, so that the chance that the location of this point is disturbed is very small. Thus, the exploration point performed according to the present invention need not be accessible and can be detected from some distance. 30 with relatively high accuracy. The present invention consists in arranging a permanent magnet on the site or in the vicinity of the point to be marked. This magnet is then detected within a distance from the magnet which depends on the strength of the magnet and the sensitivity of the detector. When the magnet is detected, the location can be accurately determined depending on the accuracy and capabilities of the detector. Basically, the axis or the plane perpendicular to the axis of the magnet can be detected 8007110 - 2 -

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as well as the distance to the detector. An exemplary embodiment of the present invention is the marking of research areas in nature. In nature, certain areas are defined by naturalists and followed for a very long time in their development. The site in question must be accurately retrieved after a long to very long time, while the appearance of the site may have changed significantly due to the vegetation.

Moreover, in such an area where tourists come, no certainty can be given of the preservation of visible landmarks, unless they are very voluminous and expensive. In the present exemplary embodiment, at one place in this terrain, one or more magnets are introduced into the ground at a depth that can be expected to be interference-free, e.g. 1.5m to 2.5m. The permanent magnets sufficiently retain their magnetism for many hundreds of years. With the aid of a gradient magnetometer of the flux-gate principle, magnetic fields with a strength of already INTesla can be detected.

With a sufficiently strong magnet, the exploration point can be located within a radius of ± 10m. After the location of the magnet is approximately known, the axis of the magnet as well as the distance to the probe can be determined very accurately. The point of intersection of the axle with the terrain surface is then the marked point, 8 0 0 71 1 0

Claims (6)

1. Marking of a point to be recorded by applying one or more bodies, characterized in that, these bodies mainly consist of a permanent magnet, 2. Marking of a point to be recorded by applying 5. or more bodies according to claim 1, characterized in that the strength of this magnet is such that the field of this magnet can be detected with a magnetometer at such a distance from this magnet that the point of detection is easy to access and that the locus of these points of detection is an area large enough to be found in a targeted search method, 3, Marking of a point to be recorded by applying 1 or more bodies according to Claims 1 to 2, characterized in that the magnet is arranged in position and direction such that the magnet t positions the magnet t, o, v, the point where the magnetometer is located can be determined and / or the location of the axis of the magnet can be determined, 4, Marking of a point to be captured by applying 20. or multiple bodies according to claims 1 to 3, characterized in that, each magnet can be recognized from the size of the reading in the detector, especially when multiple magnets are used with different values, whereby the point to be recognized is, as it were, extra coded by a combination of 25 different values, 5. Marking of a point to be recorded by applying one or more bodies according to the preceding claims, characterized in that the detector with which the magnetic bodies are detected consists of a gradient magnetometer of the flux-hole principle, Marking of a point to be recorded by applying one or more bodies according to the preceding claims, characterized in that the correct position of the magnet is fixed by arranging it firmly within a sleeve of plastics material or other material, or fixedly connected to a cone after which the magnet can be applied by lowering the magnet with sleeve or 8007110 - 4 - ί - ^ with cone in a borehole in the ground or by striking it in the ground using an impact probe, an air hammer or like that. 8007110