GB2265274A

GB2265274A - Surveying method and apparatus

Info

Publication number: GB2265274A
Application number: GB9305912A
Authority: GB
Inventors: Michael Christopher Stuttle; Richard Hogg
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-03-20
Filing date: 1993-03-22
Publication date: 1993-09-22
Anticipated expiration: 2013-03-22
Also published as: GB2265274B; GB9305912D0

Abstract

A method of surveying a cavern 2 comprises providing a bore hole 3 leading to the cavern; inserting at least the head 5 of a distance measuring device mounted on a support 6 into the cavern; fixing the position of the support relative to the walls of the cavern; and utilizing the distance measuring device to survey the cavern relative to the fixed position of the device. The distance measuring device may be a rotating pulse laser range finding device mounted on the end of a multi-section rod. <IMAGE>

Description

SURVEYING METHOD AND APPARATUS This invention relates to a surveying method and apparatus, and in the preferred embodiment provides a method and apparatus for surveying a cavern to which access can be had only via a relatively small diameter passage.

The term "cavern" as used herein is intended to cover both man-made and naturally occurring spaces.

There are many instances in civil engineering and mineral extraction when it is desirable to survey a cavern.

For example, if a cavern is encountered as a result of test boring on a site of a proposed civil engineering construction, it is highly desirable to survey the cavern to determine whether its presence is significant to the proposed project. It is, of course, relatively easy to determine the dimension of the cavern in the direction of extension of a bore hole leading into the cavern, but it is extremely difficult to measure the other dimensions of the cavern if the only access to the cavern is via a small diameter hole drilled into the cavern.

According to one aspect of the present invention there is provided a method of surveying a cavern comprising providing a bore hole leading to the cavern; inserting at least the head of a distance measuring device mounted on a support into the cavern; fixing the position of the support relative to the walls of the cavern; and utilizing the distance measuring device to survey the cavern relative to the fixed position of the support.

In a particularly preferred embodiment of the invention the distance measuring device is a laser range finding device which comprises a laser for emitting a signal in a predetermined direction relative to the device; means for detecting a reflection of said signal; and means for measuring the delay between sending said signal and receiving said reflection to determine the distance from the device from which the signal was reflected.

In the preferred embodiment of the invention the send/receive head of a laser range finding device is mounted to be rotated in a controlled manner relative to the support whereby a multiplicity of distant signals may be determined at a multiplicity of predetermined angular positions relative to the fixed position of the support.

In a particularly preferred embodiment of the invention the laser range finding device is mounted for rotation in a controlled manner about two mutually perpendicular axes whereby a multiplicity of range signals each having a known position relative to each other may be obtained in order to produce a three-dimensional survey of the cavern In the preferred embodiment of the invention means are provided for determining the relationship between the direction of any given range signal and fixed earth coordinates so that a three-dimensional plan of the cavern, fixed relative to earth coordinates, can be produced.

A particularly preferred embodiment of the invention comprises a head of a distance measuring device mounted on a support, the support being located at the distal end of a multi-section rod, the sections of the rod being interconnected in a manner which determines the angular position of each section relative to the next adjacent sections.

By this means, the orientation of the support relative to fixed ground coordinates can be determined by reference to the angular position of the proximal end of the rod relative to the said earth coordinates.

In a particularly preferred embodiment of the invention the support and/or the distal end of the rod is adapted to hang vertically from the remainder of the rod whereby, after the support and/or distal end of the rod have entered the cavern from the bore hole the support and/or distal end of the rod will assume a vertical orientation. This vertical orientation may then be used as a reference for rotation of the head of the distance measuring device about a horizontal axis enabling the inclination of any given distance measurement to be determined. Since the rotational position of the support relative to the proximal end of the rod is fixed, this fixed relationship may be used to determine the direction of any range signal relative to a vertical axis about which the distance measuring device is rotated.Hence, a threedimensional survey of a cavern, relative to fixed earth coordinates, may be produced.

Preferably, the output signal of the distance measuring device is applied to a computer programmed to produce the required three-dimensional survey from signals received from the distance measuring device. The computer is preferably programmed to control movement of the head of the distance measuring device relative to the perpendicular axes about which it is moveable and to record and plot the signals received from the distance measuring device to produce a graphic illustration of the cavern.

The distance measuring device may comprise a self-contained device located on the support. In the alternative, the support need only carry a signal emitting and signal receiving head together with controls necessary to rotate the head about the required axes. The signal generating and signal interpreting components and associated control circuitry may be located at surface level and connected to the distance measuring device head by suitable means, for example optical fibre cables and/or electrical cables.

In the preferred embodiment of the invention the rod consists of a multiplicity of sections which are permanently connected together by hinge joints which permit relative hinging of the sections, but which prevent rotation of the sections relative to each other about the axis of the rod.

The invention will be better understood from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings wherein: Figure 1 illustrates schematically a preferred embodiment of the invention; Figure 2 illustrates in greater detail the distance measuring head and associated components of the device of Figure 1; Figure 3 illustrates a preferred joint arrangement for the rod of the embodiment of Figures 1 and 2; Figure 4 illustrates feeding the rod into a bore hole; and Figure 5 is a schematic illustration of the control equipment associated with the distance measuring device.

Referring firstly to Figure 1 there is illustrated apparatus for surveying a subterranean cavern 2 to which access may be gained via a bore hole 30 The hole 3 is bored from the surface 4 of the ground above the cavern. In order to survey the cavern the head 5 of a distance measuring device is mounted on a support 6 which is in turn secured to the distal end of a rod 7 made up of a plurality of hingedly interconnected sections 8. Signal and power carrying cables extend from the head 5 and support 6 through the rod 7 to surface apparatus 9. The surface apparatus 9 in combination with the head 5 and the interconnecting cables form a distance measuring device operable to determine the distance from the head 5 to the wall of the cavern 2 along a particular axis fixed relative to the distance measuring device head 5.

Referring now to figure 2, the head 5 is mounted on the support 6 for rotation about an axis A which is perpendicular to the longitudinal axis B of the support 6.

Suitable drive means 10 are provided for rotating the head 5 about the axis A, and means are provided for determining the angular position of the head about the axis A relative to some predetermined position. By way of example only, the drive device 10 may comprise a stepping motor and gear box arrangement whereby the angular position of the head 5 about the axis A relative to a predetermined starting point may be determined by the number of steps by the motor to position the head at its position for the time being.

Further drive means 11 are provided for rotating the lower portion 6A of the support relative to the upper portion of the support about the axis B. Again, means are provided for determining the position of the support portion 6A about the axis B relative to the position of the upper portion 6B of the support. Such means may comprise a stepping motor whereby the position of the support portion 6A is known relative to a predetermined starting position.

The driving means, 10,11 may be of any suitable form, and if desired means separate from the driving means may be provided for determining the position of the head 5 about axes A and B relative to predetermined fixed positions.

The support 6 is rigidly fixed to the distal section 8 of the rod 7, and the sections 8 are interconnected to each other by joints which prevent rotation of the sections 8 relative to each other about the longitudinal axis of the rod. One suitable joint arrangement is illustrated in Figure 3 and will be seen to comprise a bar 28 having devises 29 at each end of the bar.

The devises 29 are hingedly connected to tabs 27 at the ends of the rod sections 8. The arrangement in Figure 4 permits the rod to be folded into a compact form for transportation, and to be readily extended into its use configuration as its is lowered down the bore hole as illustrated in Figure 4.

It will be noted that, because the connections between the sections 8 of the rod 7 do not permit rotation of the sections relative to each other about the axis of the extended rod, and because the upper part 6B of the support 6 is rigidly fixed to the distal rod part 8, the angular position of the support part 6B relative to the ground can be determined from the surface by inspection of the projecting portion of the rod. Hence, by aligning a suitable mark on the surface portion of the rod with a fixed earth coordinate (for example the "North" direction) the position of the support part 6B can be fixed relative to that coordinate.Since means are provided for determining the angular position about the axis B of the support portion 6A relative to the support portion 6B, once the position of the support portion 6B has been fixed relative to an earth coordinate the angular position of the support portion 6A, and with it the direction (measured about axis B) of the head 5, can be determined relative to the earth coordinate.

It will also be noted that the joints between the rod sections 8 will enable the bottom-most rod section to hang vertically within the cavern so long as the lower-most joint is clear of the bore hole. This will be true even if the bore hole itself is not strictly vertical. Hence, it may be assumed that the axis A (which is perpendicular to the axis B) is horizontal Thus, rotation of the head 5 about the axis A will cause the head to rotate in a vertical plane. By determining the angular position of the head 5 about the axis A relative to a known predetermined starting datum set by the support 6 the actual angular orientation of the head 5 relative to horizontal may be determined. Thus, both the direction of the head 5 relative to a fixed ground coordinate (e.g.North) and the direction of the head 5 relative to horizontal can be determined and the signals received from the head 5 may accordingly be used to build up a picture of the cavern which will be fixed relative to the fixed earth coordinate.

If desired, it is of course a simple matter to measure the distance from the surface 4 to the head 5 and accordingly fix the picture of the cavern in the vertical direction relative to some datum point.

In the preferred embodiment of the invention the head 5 is the head of a laser ranging device. The head 5 incorporates a laser signal emitting lens 12 which receives a laser signal from an optical fibre 13, and a signal receiving lens 14 which receives any reflection of the laser signal and transmits the received signal to an optical fibre 15.

Referring now to Figure 5 the laser ranging system is schematically illustrated. The head 5 is, as previously described, located on the support 6 and the optical fibres 13,15 extend from the head 5 to the surface.

At the surface, suitable equipment is provided for determining the distance from the head 5 to the next solid surface in front of the head 5 along the axis of detection thereof, and for controlling/recording the position of the head and the distance figures received.

The entire system is under the control of a central processor 16 which is operated from a keyboard ii.

In one typical operating mode, the head 5 will be positioned in the bore hole as previously described and the rod 7 rotated to align appropriate marks on the rod 7 with a fixed earth coordinate, e.g. North. The CPU will then be instructed by the keyboard 17 to survey the cavern.

This will result in the CPU issuing signals to a position/movement controller 18 to initialize the position of the head 5 by sending appropriate signals along a cable 19 to the drive means 10,11. Once the initial position of the head 5 has been established the CPU will cause a multiplicity of range measurements to be made for various positions of the head 5. At each position of the head 5 the CPU will issue an instruction to a trigger circuit 19 which will in turn start a clock 20 and energize a pulse generator 21 for emitting a light pulse from a laser diode 22. The pulse will travel down optical fibre 13 and be transmitted by lens 12. The reflected signal will be picked up by lens 14 and transmitted via optical fibre 15 to a photo-detector 23 the output of which is used to stop the clock 20.The resulting time elapse between starting and stopping of the clock is a measure of the distance from the head 5 to the surface from which the laser signal is reflected, and this time elapse figure is fed to the CPU 16 to calculate the distance and record the distance against the angle parameters for the head 5. The head 5 is then shifted to a new position and a further measurement made.

The CPU is preferably adapted to provide a visual display on an appropriate monitor 24 and to produce a hard copy output on a suitable data output device 25. The display preferably provides a pictorial representation of the cavern. Individual data measurements comprising information as to the orientation of the head 5 and the distance from the head 5 to the reflective surface are preferably available from a data port 26 for recording for subsequent analysis or storage.

It will be appreciated that whilst a particular embodiment of control and display apparatus has been described the invention may be operated in any appropriate manner to produce the desired information and the described embodiment should be taken as illustrative only. It will further be appreciated that appropriate control, error detection, noise reduction and other circuitry may be provided as appropriate.

Claims

1. A method of surveying a cavern comprising: providing a bore hole leading to the cavern; inserting at least the head of a distance measuring device mounted on a support into the cavern; fixing the position of the support relative to the walls of the cavern; and utilizing the distance measuring device to survey the cavern relative to the fixed position of the support.

2. A method according to claim 1, wherein said distance measuring device is utilised to emit a laser signal, a reflection of said signal is detected, and the delay between sending said signal and receiving said reflection is measured to determine the distance from the device from which the signal was reflected

3. A method according to claim 1 or claim 2, further comprising rotating said distance measuring device in a controlled manner relative to the support whereby a multiplicity of distance signals may be determined at a multiplicity of angular positions relative to the fixed position of the support.

4. A method according to any preceding claim, further comprising recording and plotting output signals from said distance measuring device to produce a graphic illustration of the cavern.

5. Apparatus for inserting through a bore hole to survey a cavern, the apparatus comprising a distance measuring device having a head mounted on a support, at least the head being adapted to be inserted in the the cavern, and means for fixing the position of the support relative to the walls of the cavern, the distance measuring device being provided with means for surveying the cavern relative to the fixed position of the support.

6. Apparatus according to claim 5, wherein the distance measuring device is a laser range finding device which comprises a laser for emitting a signal in a predetermined direction relative to the device; means for detecting a reflection of said signal; and means for measuring the delay between sending said signal and receiving said reflection to determine the distance from the device from which the signal was reflected.

7. Apparatus according to claim 6, wherein the send/receive head of the laser range finding device is mounted to be rotated in a controlled manner relative to the support whereby a multiplicity of distance signals may be determined at a multiplicity of predetermined angular positions relative to the fixed position of the support.

8. Apparatus according to claim 6, wherein the laser range finding-device is mounted for rotation in a controlled manner about two mutually perpendicular axes whereby a multiplicity of range signals each having a known position relative to each other may be obtained in order to produce a three-dimensional survey of the cavern.

9. Apparatus according to claim 7 or claim 8, further comprising means for determining the relationship between the direction of any given range signal and fixed earth coordinates so that a three-dimensional plan of the cavern, fixed relative to earth coordinates can be produced.

10. Apparatus according to any of claims 5 to 9, wherein the support is located at the distal end of a multisection rod, the sections of the rod being interconnected in a manner which determines the angular position of each section relative to the next adjacent sections.

11. Apparatus according to claim 10, further comprising means for determining the orientation of the support relative to fixed ground coordinates by reference to the angular position of the proximal end of the rod relative to the said earth coordinates.

12. Apparatus according to claim 10 or claim 11, wherein the support and/or the distal end of the rod is adapted to hang vertically from the remainder of the rod whereby, after the support and/or distal end of the rod have entered the cavern from the bore hole the support and/or distal end of the rod will assume a vertical orientation.

13. Apparatus according to any of claims 10 to 12 further comprising a computer, wherein an output signal of the distance measuring device is applied to the computer programmed to produce the required three-dimensional survey from signals received from the distance measuring device.

14. Apparatus according to claim 13, wherein the computer is programmed to control movement of the head--of the distance measuring device relative to the perpendicular axes about which it is moveable and to record and plot the output signals received from the distance measuring device to produce a graphic illustration of the cavern.

15. Apparatus according to any of claims 10 to 14, wherein the distance measuring device comprises a selfcontained device located on the support.

16. Apparatus according to any of claims 10 to 14 wherein the support carries a signal emitting and signal receiving head together with controls necessary to rotate the head about the required axes, the signal generating and signal interpreting components and associated control circuitry being located at surface level and connected to the distance measuring device head by suitable connecting means.

17. Apparatus according to claim 16 wherein the connecting means are optical fibre cables and/or electrical cables.

18. Apparatus according to any of claims 10 to 17, wherein the sections of the rod are permanently connected together by hinge joints which permit relative hinging of the sections, but which prevent rotation of the sections relative to each other about the axis of the rod.

19. Apparatus substantially as hereinbefore described with reference to the accompanying drawings.