MEASURING ASSEMBLY AND METHOD

Abstract

A base station for measurements emits measurement radiation into a beam plane with a wobbling motion of the beam plane, such that a position of a normal of the beam plane is changed in a predefined manner such that orientations of the normal occur repeatedly, for example with a cyclic repetition of the beam plane. A measuring assembly for such a base station can be provided with at least one associated remote terminal. A method for guiding a mobile object, in particular a vehicle, uses a base station and at least one active remote terminal permanently associated therewith, which form a transceiver measuring assembly.

Claims

1-15. (canceled)

16. A base station configured to perform a measurement method, the method comprising: emitting measurement radiation into a beam plane such that the beam plane wobbles in a manner by which a plurality of different predefined orientations of a normal to the beam plane occur repeatedly.

17. The base station of claim 16, wherein the base station is configured to cause the wobbling of the beam plane in a manner by which repeated occurrences of the plurality of different predefined orientations occur cyclically.

18. The base station of claim 16, comprising a rotatable beam deflector, wherein: the base station is configured to generate a wobble movement in a manner by which the normal to the beam plane rotates about a rotational axis with a temporally known phase angle; the rotational axis is non-parallel to the normal and is at a predefined angle of inclination with respect to the normal, so that the beam plane sweeps, at least twice per rotation of the normal, over an active counterpart station that is external to the base station.

19. The base station of claim 18, wherein the predefined angle of inclination is constant.

20. The base station of claim 16, comprising: an optoelectronic emitter, wherein the optoelectronic emitter is configured to generate the measurement radiation; a collimator, wherein the collimator is configured to collimate the measurement radiation generated by the optoelectronic emitter; and a beam expander, wherein the beam expander is configured to expand the collimated measurement radiation from the collimator to form the wobbling beam plane of emitted measurement radiation.

21. The base station of claim 20, comprising a modulator, wherein the modulator is configured to modulate the measurement radiation generated by the optoelectronic element with a data signal.

22. The base station of claim 21, wherein the data signal encodes at least one of (a) angle information, (b) an inclination of an inclination sensor, (c) a unique identifier of the base station, (d) a temperature of the base station, and (e) a battery status of the base station.

23. A measurement beam receiver configured to perform a method, the method comprising: receiving beams emitted from a base station in a beam plane that wobbles in a manner by which a plurality of different orientations of a normal to the beam plane, which are predefined in the base station, occur repeatedly.

24. The measurement beam receiver of claim 23, wherein the method further comprises, based on repeated detections by the measurement receiver of the wobbling beam plane, determining data regarding at least one angle in relation to a polar coordinate system of the base station.

25. The measurement beam receiver of claim 24, wherein: the method further includes determining respective points in time of the detections, and the determination of the data is based on the determined points in time; and/or the method further includes determining at least two angular positions of the beam plane normal rotating as a result of the wobbling at the respective points in time of the detections, and the determination of the data is based on the determined at least two angular positions.

26. The measurement beam receiver of claim 25, wherein: the method includes the determining of the angular positions, and the determining of the angular positions is performed by decoding the radiation modulated with an angle-encoding data signal; and/or the method includes calculating at least one vertical angle relative to the polar coordinate system of the base station and/or at least one horizontal angle relative to the polar coordinate system of the base station.

27. The measurement beam receiver of claim 23, comprising: at least two light-sensitive elements that are spaced apart from one another and that are arranged at different heights during operation, wherein the measurement beam receiver is configured to resolve an ambiguity of measurements based on a time signature of a sweeping of the emitted beams over the at least two light-sensitive elements.

28. A method using a base station, at least one active counterpart station that is fixedly related to a mobile object, and a stationary active counterpart station is set up in stationary fashion, the method comprising: ascertaining a virtual connecting line between the base station and the stationary active counterpart station; ascertaining guide data for guidance of the mobile object based on beam detections related to the active counterpart station that is fixedly related to the mobile object and the virtual connecting line; and guiding the mobile object based on the ascertained guide data.

29. The method of claim 28, wherein the ascertainment of the guide data is performed by determining a plane in which the connecting line lies and which additionally has a defined transverse inclination.

30. The method of claim 29, wherein the ascertainment of the guide data is performed by determining a target guide line in the plane.

31. The method of claim 28, wherein the virtual connecting line includes a chain of segments of a virtual guide wire along which segments the base station, other base stations, the stationary active counterpart station, and other stationary active counterpart stations alternate.

32. The method of claim 31, wherein: respective portions of the guide data are determined for different ones of the segments and the method further comprises smoothing the portions of the guide data; and/or the method further comprises interpolating transition points of the segments.

33. The method of claim 32, wherein the guide data includes control parameters for an automatic movement of the mobile object.

34. The method of claim 33, wherein the method comprises the interpolating of the transition points of the segments, and wherein the interpolating is performed with reference to additional information.

35. The method of claim 34, wherein the additional information includes odometer values.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0095] FIGS. 1a-1d show four different exemplary measuring assemblies from the prior art.

[0096] FIG. 2 shows an overview of a measuring assembly according to an example embodiment of the present invention.

[0097] FIG. 3 shows a measuring assembly with an active target according to an example embodiment of the present invention, the reception signature of the active target being represented for two different heights.

[0098] FIG. 4 shows a measuring assembly with an active counterpart station comprising two receivers, one vertically above the other, at a known distance b, in order to eliminate ambiguities and to determine 3D coordinates relative to a base station, according to an example embodiment of the present invention.

[0099] FIG. 5 shows a measuring assembly with an active target, the latter being assigned a GNSS antenna for eliminating an ambiguity, where the 3D coordinates of the GNSS antenna can be improved by the active target, according to an example embodiment of the present invention.

[0100] FIG. 6 shows a measuring assembly with two base stations for eliminating an ambiguity with base distance b and for determining 3D coordinates of an active target, according to an example embodiment of the present invention.

[0101] FIGS. 7a-7f show six alternative arrangements of optical components in the base station, according to example embodiments of the present invention.

[0102] FIG. 8 shows a sectional view through optomechanics of the base station, according to an example embodiment of the present invention.

[0103] FIG. 9 shows a block diagram of a control circuit of the base station, according to an example embodiment of the present invention.

[0104] FIG. 10 shows a block diagram of an active target, according to an example embodiment of the present invention.

[0105] FIGS. 11a-11d show examples and elucidations concerning a possible configuration of the angle-encoded data signals in the base station and after reception in the active target, according to example embodiments of the present invention.

[0106] FIG. 12 shows a conventional attachment of laser sensors to construction machines in a method for guiding construction machines in road construction.

[0107] FIG. 13 shows a plan view of a course of a road in a conventional method.

[0108] FIG. 14 shows an attachment of active targets in the case of a method for determining height and location of a vehicle, according to an example embodiment of the present invention.

[0109] FIG. 15 shows virtual laser planes and an interpolation at the transition between the support points when implementing a method according to an example embodiment of the present invention with a virtual guide line or string line.

[0110] FIG. 16 shows a plan view of a course of a road and a road paver when implementing the method also elucidated by FIG. 15 with a virtual string line.

DETAILED DESCRIPTION

[0111] FIG. 2 shows a measuring assembly designated generally by 1 and comprising a base station 2, which emits measurement radiation into a plane, wherein the base station 2 is configured for a wobble movement of the beam plane 4, by means of which wobble movement the location of the normal 6 to the beam plane 4 is changed in a known way such that a series of orientations of the beam plane normal 6 are gone through in a known way, cf. phase angle ψ (psi). Furthermore, the measuring assembly 1 comprises an active counterpart station 3 for receiving the measurement radiation emitted by the base station 2, i.e., an active target 3.

[0112] In the exemplary embodiment illustrated, the base station 2 is arranged on a sufficiently stable tripod stand 36 and emits visible light as measurement radiation. In the exemplary embodiment illustrated, the base station 2 is situated such that an axis 8 is aligned perpendicularly. As will also be explained with reference to FIGS. 7a-7f, beam deflecting optical elements rotate about the axis 8 in the base station 2. In this case, the wobble movement of the exemplary embodiment in FIG. 2 is effected such that the normal 6 to the beam plane 4 is inclined relative to the axis 8 by an angle α (alpha) and an end point of a normal unit vector 6 intersecting the axis 8 rotates on a circle about the axis 8. The phase angle ψ (psi) indicates what phase of the circular rotation said normal vector is in.

[0113] The active target 3 can for example be secured to an object to be measured (not shown) in a releasable or nonreleasable manner, be held on said object or be installed fixedly or movably in order to measure a position thereat. It will be understood that the wobbling beam plane sweeps over an active counterpart station 3 arranged at a suitable height twice during each wobble cycle. The active target 3 comprises a light-sensitive element in order to generate a characteristic signal in each case during the reception of the measurement radiation that is brought about as a result of sweeping over. From the signature of said characteristic signal, symbolized by the curve at the receiver 42 in FIG. 2, it is possible to deduce the orientations of the normal at those times at which the measurement radiation is received, as will also be described further below.

[0114] In order to generate a wobbling beam plane, an optoelectronic beam transmitting element 12 is arranged in the base station 2, cf. FIGS. 7a-7f, wherein optical elements that shape and deflect the beam of the optoelectronic beam transmitting element 12 are disposed downstream thereof. There are a multiplicity of optical assemblies that can be used to achieve the desired wobble movement of the beam plane 4. Some of said multiplicity of optical assemblies shall be described with reference to FIGS. 7a-7f.

[0115] FIG. 7a shows the arrangement of the optical components of a particularly preferred variant of the base station 2. In this case, the optoelectronic beam transmitting element 12 is a laser diode 12 that emits a divergent beam. The latter is converted into a largely parallel collimated beam by means of a collimator 10, which is configured as a biconvex lens of optimum shape in the exemplary embodiment illustrated. Said collimated beam subsequently impinges on a rotating beam deflecting component 7, which is a rotating angular prism in the exemplary embodiment illustrated in FIG. 7a. In this case, the angular prism rotates about the rotational axis 8, which is in turn parallel to the propagation of the collimated beam 11.

[0116] In the exemplary embodiment illustrated in FIG. 2, the rotational axis 8 is perpendicular and the wobbling beam plane 4 has a normal vector 6 that is inclined relative to the perpendicular rotational axis 8 by the deflection angle alpha. For driving the rotation of the angular prism, provision is made of an electric motor 18 that generates the rotational movement, said electric motor merely being illustrated schematically in FIG. 7a.

[0117] In the exemplary embodiment shown in FIG. 2, the collimated beam that is thus cyclically deflected into different directions according to an angular prism rotation which different directions however are always oblique relative to the perpendicular 8, is then incident on a 90° conical mirror 5, which converts the deflected collimated beam into a beam plane 4 and inclines it further in the process.

[0118] In this case, the inclination of the beam plane 4 downstream of the conical mirror 5 is such that the normal 6 to the beam plane 4 is oblique at the angle alpha with respect to the perpendicular rotational axis 8. As evident from FIG. 2, the normal 6 rotates cyclically about the perpendicular 8 according to the angular prism rotation, such that the beam plane normal 6 repeatedly assumes the same orientation while the angular prism rotates, and wherein the instantaneous orientation of the beam plane normal 6 is known at any time, provided that it is known how the angular prism is instantaneously oriented as a result of the angular prism rotation about the perpendicular rotational axis 8, said rotation being brought about by the rotary motor 18. One preferred possibility will also be indicated below as to how an instantaneous orientation of the angular prism can be determined by means of the angular prism rotation brought about by the rotary motor 18 and can be communicated to the active target 3.

[0119] Since the conical mirror 5 expands the deflected, collimated beam to form a beam plane, a beam expanding component is realized in this respect.

[0120] In the case of the exemplary embodiment illustrated, it should be noted that the beam plane has a finite thickness and this thickness is moreover different in different directions. This is discernible from FIGS. 7a and 7b. This effect of varying thicknesses can best be understood if it is assumed that the vertex of the conical mirror 5 lies exactly over the perpendicular axis 8 and, moreover, the axis of symmetry of the conical mirror extending through the vertex of the conical mirror 5 lies exactly on the perpendicular axis 8. It should furthermore be assumed that the collimator collimates the radiation from the optoelectronic beam transmitting element 12 to form a precisely circular and homogeneous beam of parallel individual rays. (It should explicitly be pointed out that these assumptions of an exact alignment are made only in order to be able to better explain the effect of the different thicknesses, but that the realization of the assumptions is not absolutely necessary for the practical implementation and the invention or the particular exemplary embodiment is in no way intended to be restricted to the assumed exactness. It should therefore be explicitly pointed out to the readers that neither an exact arrangement of the conical mirror vertex on the perpendicular axis, nor the exact coaxial alignment of the axis of symmetry of the conical mirror extending through the vertex of the conical mirror 5 with the perpendicular axis, nor an exactly circular beam collimated exactly without divergence as described are required in practice, rather respective inaccuracies and deviations may be readily accepted or, where a higher precision is desired, corrections of inaccuracies are possible. The fact that high structural precisions in the direction toward the simplifying assumptions made for the sake of better explanation can nevertheless be achieved without great outlay should be mentioned, however.)

[0121] Under the simplifying assumptions made in respect of the conical mirror alignment, it can be understood particularly well why the beam thickness varies in different directions, by considering for two directions in each case central rays, or rays lying at the outer edge of the collimated beam, namely those in the direction with the greatest rising beam plane inclination away from the conical mirror 5 or the corresponding rays in the direction diametrically opposite thereto with the greatest falling beam plane inclination.

[0122] The central rays of the collimated beam impinge on the conical mirror 5 very near to the cone vertex. They will define the lower limit of the beam plane in each case, that is to say in that direction in which the beam plane rises and in the diametrically opposite direction in which the beam plane falls. Since the collimated beam is inclined relative to the perpendicular 8 and thus the conical mirror axis, the outer rays of the beam propagate toward the perpendicular axis 8 on one side, however, whereas the outer rays propagate away from the perpendicular axis 8 on the diametrically opposite side. Accordingly, the outer rays of the collimated beam impinge on the conical mirror 5 at different heights in each case. This is readily discernible in FIG. 7a. This impingement at different heights has the effect, after the deflection by the conical mirror 5, that the thickness of the beam plane is different toward the different directions. FIG. 7b shows that the thickness of the beam plane changes in a direction according to the change in the beam inclination. In this case, FIG. 7b shows the same assembly as FIG. 7a, except that here the location of the beam paths is additionally shown in a dash-dotted manner for a position of the angular prism rotated further by 180°.

[0123] It should be noted that the different thickness has an effect in the event of the determination of when the wobbling beam plane sweeps over a light receiver.

[0124] This effect is accurately calculable, however, and can be compensated for computationally. Moreover, the vertex of the conical mirror can almost touch the surface of the angular prism without beam shadings of the beam plane if the angle of inclination of the beam plane corresponds exactly to the prism angle, which is the case given a refractive index of 2.0 for the material of the angular prism. The corresponding imaging aberrations that result in the varying thickness are thus noncritical in practice.

[0125] FIG. 7c shows that and how the above-described offset problems that alter the beam plane thickness can largely be compensated for optically. The optical elements used for beam deflection in this exemplary embodiment comprise, in addition to an angular prism 7 once again used, a plane-parallel plate arranged between the collimator 10 and the angular prism 7 in the beam path, said plane-parallel plate being tilted relative to the axis of the collimated beam. The tilted plane-parallel plate is coupled to the angular prism 7 for conjoint rotation, such that the tilted plane-parallel plate concomitantly rotates upon rotation of the angular prism 7 in FIG. 7c. In this exemplary embodiment, the beam deflecting component thus also comprises a tilted parallel plate in addition to the angular prism.

[0126] FIG. 7d shows a further embodiment, which differs from that in FIG. 7a insofar as in FIG. 7d the parallel collimated beam is reshaped into a ring beam, that is to say has an intensity over the cross-sectional area which is only low in the center and which has a ring-shaped region of higher intensity at a distance from the center. This ring beam profile is obtained by two axicons being added to the collimator. The ring beam profile has advantages with regard to the divergence of the beam plane in the vertical, for which reason a beam of given power is still detectable at a greater distance from the base station 2. The range of a base station 2 and the measurement accuracies achievable with a base station 2 can be improved using such a ring beam profile.

[0127] In the exemplary embodiment in FIG. 7e, the conical mirror 5 from FIG. 7a is replaced by a 90° planoconcave axicon. In the exemplary embodiment, the planoconcave axicon illustrated is formed as a right circular cylinder with a plane end face toward the light transmitter 12 and with a conical recess on the end face that faces away from the light transmitter 12. The surfaces of this planoconcave axicon are optically polished. A beam that enters the plane end face of the planoconcave axicon from the side of the light transmitter 12 is deflected by total internal reflection at the conical recess and emerges from the lateral surface. The use of such a planoconcave axicon has advantages for the mechanical design of a base station 2 because the axicon—unlike a conical mirror—can be held easily without a glass tube, a glass housing or even nontransparent clip structures shading parts of the beam or attenuating beams as they pass through.

[0128] By virtue of its cylindrical shape, the axicon shown, in particular below the beam exit region, can be held with little outlay jointly with the rotating beam deflecting optical elements coaxially with respect to the rotational axis, for example in a suitable tube. However, it should be pointed out that the vertex of the conical recess of the axicon cannot be arranged as near to the exit surface of a beam deflecting angular prism as is the case for the vertex of the conical mirror 5 from FIG. 7a. Since for this reason the above-described deflection—resulting in different beam plane thicknesses—by the rotating angular prism would have a greater effect, it is preferred to use, where instead of the conical mirror 5 a planoconcave axicon is used, instead of the single rotating angular prism from FIG. 7a two angular prisms working in relation to one another, which deflect the beam to different extents and which jointly ensure that the deflected beam impinges centrally or almost centrally on the conical surface of the planoconcave axicon.

[0129] An embodiment which admittedly does not yield particularly high measurement accuracies, but does permit particularly small structural sizes and extremely low costs, is shown in FIG. 7f. In this exemplary embodiment, the means for beam deflection is identical to the means for beam-to-beam plane expansion. In other words, here the beam deflecting component 7 is identical to the beam plane expanding component 5. In this case, a conical mirror 5 is used, the axis of symmetry of which is tilted by an angle alpha/2 with respect to the rotational axis 8 (perpendicular in FIG. 2). This constitutes an outstandingly simple solution, but is beset by problems in the stability of the deflection, since dynamic errors of the mechanical mounting of the rotational axis in the case of a customary design and customary angles of inclination of the normal to the wobble plane have an effect more than 10× greater than in the case of the arrangement from FIG. 7a. This variant from FIG. 7f should therefore only be given preference if what is important is not extremely high measurement accuracy, but rather extremely small structural size and extremely low costs, such as e.g., in the case of the miniaturized integration of the base station into a smartphone or the like.

[0130] The optical components shown allow an advantageous optomechanical design of base stations 2. This will be explained by way of example with reference to FIG. 8 for a mechanical set-up of an embodiment that largely corresponds to the configuration from FIG. 7a.

[0131] In this case, FIG. 8 shows a sectional view through the optomechanics of this particularly preferred variant of the base station 2.

[0132] In this case, the optoelectronic beam transmitting element 12 is a laser diode that emits a divergent beam. The divergent beam is converted into a parallel beam, said beam being focused (on infinity), by a collimator lens 10. As is evident, the laser diode 12 and the collimator lens 10 are mounted fixedly with respect to one another. They are situated in the interior of a hollow shaft 8, which is rotatable around them and which is fixedly connected to the angular prism 7; more precisely, the angular prism is inserted into the hollow shaft.

[0133] The hollow shaft is mounted such that it is rotatable by a bearing unit 9, which is pretensioned without play, and is driven by the rotary drive realized as a brushless motor 18 and is thus caused to rotate jointly with the angular prism. For this purpose, the motor 18 comprises a stator 19 and a magnetic rotor 20 connected to the hollow shaft for conjoint rotation. In this case, an encoder disk 21 is simultaneously fitted on the rotor, and is scanned by two encoder read heads 22. From the signals obtained during the scanning of the encoder disk 21 with the aid of the encoder read heads 22, the rotation angle of the magnetic rotor can be determined in real time and at the same time a centering error of the encoder disk and bearing run-out can be compensated for.

[0134] Since the collimated beam deflected by the angular prism is incident on the conical mirror 5, which, as discussed above, expands the beam to form an oblique beam plane and results in the desired known wobbling of the beam plane upon rotation of the angular prism, from the signals which are obtained by the encoder read heads 22 as a result of the scanning of the encoder disk 21 not only is it possible to determine the rotation angle of the magnetic rotor in real time, but at the same time the rotational alignment of the angular prism and therefore the phase angle in the movement cycle of the beam plane normal 6 are also known.

[0135] In order to protect the optical components, the base station comprises, on the beam exit side, a transparent cover 38 shaped as a glass housing or preferably as a glass tube closed at the end side, through which cover the wobbling beam plane emerges into the measurement space to be measured.

[0136] For controlling in particular the beam emission by the laser diode 12 and the rotary drive by the motor 18, a control unit 23 is provided, which detects the electrical rotation angle signals of the encoder read heads 22 and generates therefrom a data signal 14 (angle-encoded with the aid of angle calibration data), which is fed to the driver circuit 13 of the laser diode 12 for the modulation of the radiation power.

[0137] FIG. 9 shows a block diagram of said control unit. The control unit comprises a power supply 24 and interfaces for calibration and debugging. The control unit furthermore comprises suitable encoder and motor electronics 25, via which it is connected to the motor 18 and the encoder read heads 22 such that a central computing unit 33 can define the rotational speed of the motor.

[0138] Preferably, the controller furthermore manages not only a user interface 27 but also a wireless reader 26—embodied e.g., using RFID or NFC technology—for position tags or transponders 37 that can be arranged on the stand 36 or attached to the connection point between stand and base station (e.g., to the tripod, tribrach or leveling plate) and correspond to previously ascertained absolute positions, such as can be measured for instance in advance of surveying by means of static GNSS. Such a reference to absolute positions calibrated by means of static GNSS or tachymetrically, for example, for the stands of the base stations makes it possible, where a virtual guide line is desired, to establish an extended virtual guide line with only a small number of base stations that move along according to construction progress, which results in a considerable reduction of costs by comparison with the prior art with at the same time improved handling by the users.

[0139] It should be mentioned that the approach of the calibration of base station installation points with respect to static absolute positions, in particular with the aid of static GNSS or tachymeters, and storage of these data in a transponder on the stand or installation point of the base station is considered to be advantageous by comparison with the prior art and it is considered to be inherently protectable to set up e.g., a virtual guide line with base stations which move along from one statically calibrated position to a next statically calibrated position according to construction progress. The right to file divisional applications directed thereto is explicitly reserved. It should be emphasized that such a method is also applicable using conventional base stations that do not emit beam planes wobbling in a defined and detected way. This method is likewise applicable in particular to tachymeters known from the prior art and to dual-slope lasers and the like.

[0140] Where the controller 23 is configured to detect absolute positions, for example absolute positions of previously measured position tags, the control unit 23 is preferably configured to modulate the beam that can be received by the active targets in such a way that the absolute position of the respective base station 2 is communicated to said active targets regularly, for example every few seconds. The absolute position in this respect constitutes auxiliary information that can be modulated on the radiation emitted by the base station. It should be mentioned that there is optionally also the possibility of providing the base station 2 with a dedicated GNSS receiver, which can obviate a prior measurement of desired installation positions for the base stations 2.

[0141] The base station 2 furthermore comprises an inclination compensator 28, which outputs an inclination-indicative signal to the controller 23, which signal can likewise be used for the repeated modulation of the emitted radiation.

[0142] In the preferred embodiment illustrated, the control unit 23 comprises an interpolation circuit 31, by means of which those data words which encode the angular positions are output at positions calibrated exactly with respect to the encoders. By virtue of corresponding correction data being stored in a calibration memory 32, in this case encoder disks with relatively poor linearity can be calibrated so accurately that highly accurate angle data are generated despite relatively poor linearity. The correction data necessary for this purpose can readily be determined and stored during production for each encoder disk; it should be pointed out that the calibration memory can be designed in particular as a nonvolatile memory.

[0143] The interpolation circuit 31 converts the angle data related preferably to integral indexes for fixed angular steps, and preferably also other auxiliary information, into a data format suitable for the modulation of the radiation and in this case, also ensures the presence of redundancies and checksums as necessary.

[0144] One variant that is preferred over the transmission of angle information at fixed angular positions consists in transmitting angle information at fixed time intervals. The angles thus given at fixed points in time can be determined in the base station by interpolation of the angle encoder data and can then be transmitted as angle information at the fixed points in time. This has the advantage that at the active counterpart station the beginning of data words can be detected very well even without emphasized start pulses. This in turn is advantageous because the available laser power can be better utilized and the range of the base station can thus be increased.

[0145] As data formats appropriate for optical data transmission, for example the MPPM format or a modified MPPM signal with eight symbols, i.e., optical pulses, at 128 positions should be mentioned, which allows an encoding of 40 bits of information per data word. The use of a PPM data transmission protocol, that is to say also of data protocols other than the MPPM protocol, for modulation onto the measurement radiation emitted by base stations is considered to be inventive per se, specifically also for base stations, rotary lasers and the like that are otherwise designed according to the prior art.

[0146] Before this data protocol used is explained in greater detail, the set-up of the active counterpart station 3 will be discussed. This is expedient insofar as the data protocol advantageously used is configured such that particularly high accuracies can be achieved with inexpensive, robust receivers.

[0147] FIG. 10 shows the block diagram of the active counterpart station associated with the above-described base station 2, i.e., of the active target 3. The active target 3 comprises, particularly for use with construction machines, a receiving collimator 40, by which light is focused onto a light guide 41 and is coupled into the latter. The light guide 41 guides radiation arriving from the base station 2 onto a light-sensitive optoelectronic element such as a photodiode. The light guide 41 can be a polymer optical fiber (POF), in particular, which can have a length of a plurality of meters and allows a spatial separation between the entrance region for radiation into the active target 3 and the optoelectronic and electronic components used for the detection and evaluation of a radiation reception signature.

[0148] When the beam plane sweeps over the receiving collimator 40, the light radiation is focused onto the light guide 41 and coupled into the latter. The receiver 42, which can be realized as an independent component and, in the case of construction machine applications, for example, can be fitted securely in the machine interior, is thus connected to the outside world only via the light guide 41, which can have a length of a plurality of meters.

[0149] In the case of such an assembly, the actual measurement point lies on the receiving collimator 40, which can be attached to the exterior of a construction machine, which affords considerable advantages inter alia with regard to the total vibration sensitivity and the water-tightness of the assembly. An optical filter for suppressing stray optical radiation can be assigned to the light-sensitive optoelectronic element, wherein a bandpass filter 43 having a wavelength passband with a width of only a few nanometers around the emission wavelength of the base station 2 is typically used. Said filter can lie for example upstream of an entrance lens into the receiving collimator 40, within the receiving collimator 40, between the receiving collimator 40 and the light guide, or between the light guide and the light-sensitive electronic element. It is preferred here, however, to provide the optical filter as near as possible to the optoelectronic element, since a filter having only a small structural size is typically usable in such a case, which affords price and weight advantages.

[0150] The preferably optically filtered light is then incident as an optical reception signal 44 on the light-sensitive optoelectronic receiving element 45. It is particularly preferred to use for this a customary avalanche photodiode (APD) or a linearly operated silicon photomultiplier, the bias voltage of which is controlled by the computing unit 53.

[0151] The light-sensitive optoelectronic receiving element outputs an electrical signal, which is passed into a signal conditioning circuit 48, a transimpedance amplifier (TIA) with an analog matched filter being used in the present example. The analog output signal obtained after signal conditioning is in turn converted into data of a digital data stream 50 by a high-speed ADC 49. Said data stream is fed to a digital preprocessing and compression circuit 51, which digitally conditions the received data stream further by eliminating from the data stream noise and useless or disturbing signals such as disturbance events as a result of scattered light, in order to feed to a downstream computing unit only those data of the data stream which are actually necessary for further processing. Such a digital data stream conditioning thus compresses the data stream.

[0152] It is advantageous that such a data compression is able to be carried out using particularly inexpensive data processing units, in particular because the same data processing steps have to be carried out repeatedly. Particularly configurable modules such as FPGAs are suitable for such steps. Since these have only a low power consumption and make it possible to use a computing unit having comparatively low computing power for the further processing of the compressed data stream, the use of a data compression is advantageous overall. It should be mentioned in this regard, in particular, that the use of an FPGA-based data compressor enables the power consumption otherwise required to be reduced to approximately 1/10, which is advantageous particularly where the active targets 3 are intended to be configured as fully integrated handheld receivers supplied by means of batteries, preferably fully integrated handheld receivers without the abovementioned light guides. It should be mentioned, however, that particularly where the power consumption is of secondary importance at most and a computing unit with sufficiently high computing power is simultaneously available, the compressor 51 could also be dispensed with.

[0153] It should be mentioned as being preferred that the receiver, i.e., the active target 3, is furthermore equipped with communication interfaces 54, in the present case in particular for the radio link via WLAN, in order as necessary to communicate with other active targets 3 and to pass on calculated position information.

[0154] By means of the measuring assembly 1 described, comprising the base station 2, which generates a beam plane wobbling in a known way, and an active counterpart station 3, it is possible to determine at what angle relative to the horizontal an imaginary connecting line between the active counterpart station, on the one hand, and the wobble center of the beam plane, on the other hand, said wobble center lying in the base station two, rises. This angle of inclination is referred to hereinafter as a vertical direction angle. It is designated by the Greek letter λ (lambda) in FIG. 2.

[0155] If, in accordance with FIG. 2, the intention is to indicate the position of the active counterpart station 3 relative to the base station 2 in spherical coordinates, the center point of which is the center of the beam plane wobble movement, then a horizontal direction angle and the distance with respect to the base station 2 are also required in addition to the vertical direction angle. It goes without saying that a direction with 0° has to be defined for the vertical direction angle and the horizontal direction angle. For the vertical direction angle, an exactly horizontal direction with a gradient of zero is particularly excellent. For the horizontal direction angle, by contrast, the direction can be defined arbitrarily per se. While directions such as north would be particularly excellent in practice, in the present case it can be regarded as sufficient if the horizontal direction angle is related to that direction defined as 0° to which the phase angle in the movement cycle of the beam plane normal is related. It has already been explained in this regard above that the phase angle in the movement cycle of the beam plane normal corresponds to a rotation angle of the rotary motor driving the angular prism, and that said rotation angle can be determined by means of an angle encoder. Without restricting the generality, the 0 direction thereof can be used for defining the horizontal direction 0°.

[0156] The use of the above-described optics in the base station 2 has the effect, on account of the wobble movement generated in a targeted manner, that the beam plane normal 6 rotates on a circle as illustrated in FIG. 2, wherein each active counterpart station 3 is swept over twice per circular rotation, that is to say per wobble cycle (in any case insofar as the radiation entrance surface of the active counterpart station 3 is situated between the highest height and the lowest height that can be assumed by the beam plane). The sweeping over occurs at specific phase angles. If the two phase angles ψ.sub.1 and ψ.sub.2 at which the active counterpart station is swept over are known, then the horizontal direction angle is firstly calculated simply from their average value, that is to say corresponds to (ψ.sub.1+ψ.sub.2)/2.

[0157] For determining the vertical direction angle λ (lambda), that is to say the rise or fall angle of an imaginary connecting line between, on the one hand, the active counterpart station and, on the other hand, the wobble center of the beam plane, said wobble center lying in the base station 2, it is necessary additionally to use the angle at which the normal 6 to the beam plane 4 is inclined relative to the perpendicular axis 8. This angle is designated as angle α (alpha) in FIG. 2.

[0158] With given phase angles ψ.sub.1 and ψ.sub.2 at which the wobbling beam plane 4 sweeps over the active counterpart station 3, with these variables it is possible to calculate the vertical direction angle λ (lambda) in accordance with:

[00001]$\lambda =a\tan \left(\tan \left(\alpha \right).Math.\cos \left(\frac{{\psi }_2-{\psi }_1}{2}\right)\right)$

[0159] FIG. 3 shows symbolically in this respect how the spacing of the sweeping-over events is affected if the active target at a given distance from the base station 2 varies its height. The change in height is accompanied by a variation of the temporal spacing of the sweeping-over events because the beam plane 4, depending on the target height, requires a different period of time in order, after a first sweeping over, to continue to wobble to an alignment in which the second sweeping over is observed. The time durations of different lengths clearly correspond at the same time to rotations to different extents of the beam plane normal 6 going through its movement cycle. It is also evident from FIG. 3, however, that the average point in time between the two instances of sweeping over is not dependent on the target height. It should be emphasized that this behavior fully accords with and is expressed in the formulae indicated above.

[0160] It should be noted, however, that in the case of the simple assembly such as that from FIG. 2, firstly only the signature of the repeated sweeping over of the active counterpart station 3 by the beam plane 4 is detected, but in this case it is not unambiguous as to whether an observed signature occurs at a height above or below the horizontal. (In the equation above, that has an effect as a result of sign ambiguities.)

[0161] Although it would be possible to avoid such an ambiguity by restricting the measurement space to a half-space, it is also possible using comparatively simple measures to resolve the ambiguity without such a significant restriction of the measurement space. In this respect, attention shall be drawn to the possibilities that are described below with reference to FIGS. 4-6.

[0162] FIG. 4 shows a proposal for resolving the ambiguity by arranging two active counterpart stations 3a and 3b one above the other, which makes it possible to unambiguously ascertain the heights of the individual active counterpart stations from the hence four instances of sweeping over detected. It should be emphasized that, optionally, it is not necessary to use two identical, completely separate active counterpart stations, rather that it is likewise possible to provide a single counterpart station with two light receivers or light collimators arranged one above the other. A particularly suitable active counterpart station 3 thus has more than one individual light receiver. What is particularly advantageous about this assembly is that where the vertical distance b between the light receivers arranged one above the other is known, the distance between the active counterpart station 3 and the base station 2 can also be determined. Accordingly, having recourse to the base distance b, it is possible, given a known height of the beam wobble center, to calculate the height coordinate z of the active counterpart station 3 and the distance r between the active counterpart station 3 and the base station 2.

[0163] Accordingly, by means of a receiver assembly as illustrated in FIG. 4, it is possible to determine the 3D position of the active target 3 in the polar coordinate system of the base station. It should be pointed out that where additional receivers are provided, the accuracy can be increased by interpolation and/or, given suitable positioning of even further additional receivers on the active counterpart station 3, the orientation of the active counterpart station 3 in space also becomes detectable.

[0164] Moreover, it is advantageous if, without adversely affecting the measurement accuracy, it is possible to permit the connecting line between the two receivers 3b and 3b to run not exactly vertically, but rather in a manner tilted relative to the vertical. In one preferred embodiment of the active counterpart station 3 described with reference to FIG. 4, the active counterpart station 3 is therefore provided with an inclinometer, the measured values of which can be used for compensation of a current tilting.

[0165] FIG. 5 shows as an alternative and/or additional possibility that the ambiguity can be resolved by linking the active target 3 with the position and/or location information of a GNSS antenna. At the same time, where the absolute positions determined by means of GNSS are required, the accuracy of the GNSS measurements can be increased if reference is made to a calibrated absolute position of the base station 2 and the positions determined relative thereto with the active counterpart station 3. The accuracy of the GNSS position can be significantly improved in particular with regard to the height measurement. The assembly is advantageous in this respect in particular where highly accurate absolute positions are absolutely necessary.

[0166] FIG. 6 shows a further assembly, by means of which an ambiguity is automatically resolvable. In this case, two base stations 2a and 2b are installed with a known base distance b and are calibrated with respect to one another with regard to their horizontal axes. For an active target 3 that is situated in the measurement space of both base stations, that is to say can receive the radiation from both stations for measurement purposes, the 3D position of the active target 3 can then be determined by 3D triangulation.

[0167] In this case, particular preference is given to an implementation such that passive targets 34a and 34b are fitted on each of the two base stations 2 used, specifically preferably in alignment with the rotational axis of the respective other station, wherein the base stations then, as described above, are themselves also designed for receiving radiation, specifically in such a way that in addition to horizontal angles and vertical angles, by determining a pulse time of flight from a first base station to the reflective passive target of the second base station and back, it is also possible to measure the transverse distances between the two base stations.

[0168] Such a configuration has the advantage that the stations can automatically calibrate themselves upon installation and the information obtained about the respective neighboring station can be concomitantly transmitted to an active counterpart station 3 as auxiliary information by means of a modulation of the radiation, without said active counterpart station having to initiate the calibration process or interrogate the results thereof by way of a radio interface. In this case, the installation process is as simple as in the case of a total station.

[0169] As far as the height determination is concerned, in all variants it would be sufficient, in principle, merely to determine the sweeping-over times and then to assume a synchronous rotational speed of the angular prism. However, this not only limits the accuracy as soon as fluctuations in synchronism occur, but also does not permit the complete determination of all coordinates of the active counterpart station 3. It was therefore assumed in the explanations above that the actual rotation angles of the angular prism rotation or the phase angle in the movement cycle of the beam plane normal itself shall be known.

[0170] It has already been pointed out that corresponding information can be ascertained by means of an angle decoder and corresponding angle data can be modulated on the radiation from the base station 2.

[0171] Details concerning a data protocol that is particularly suitable for the modulation of the optoelectronic beam transmitting element, here the laser diode 12, will now be described with reference to FIGS. 11a-11d.

[0172] In this respect, it should firstly be recalled that the wobbling beam plane 4 as explained above has a thickness which can vary in different directions but is in any case regularly finite. Accordingly, during the process of sweeping over the receiver, a finite time elapses from when the first rays impinge on the receiver until the last rays move away from the receiver. Firstly, the time of this beam reception is sufficient for receiving encoded information. Secondly, during this time, the wobbling beam plane will also continue to move, i.e., the phase angle of the beam plane normal 6 changes during the sweeping over.

[0173] This can firstly be used for receiving a sequence of temporally encoded data and can secondly be taken into account in order to increase the measured value precision.

[0174] It is preferred to transmit for this purpose in particular a respectively current rotation angle alignment of the rotating angular prism and thus information about a respectively current phase in the movement cycle of the beam plane normal from the base station 2 to the or each active counterpart station 3. A suitable protocol for data which can be modulated on the radiation emitted by the base will be explained with reference to FIGS. 11a-11d.

[0175] In this respect, FIGS. 11a-11c show the temporal profiles of the radiation power of the radiation emitted by a base station, said profiles being characterized by the information modulated thereon.

[0176] Accordingly, the preferred implementation illustrated uses a here 40-bit wide data word 15 constructed in each case from a start symbol for the synchronization, said start symbol being easily recognizable at the receiver, and from 8 subsequent data symbols. The respective symbols are realized by generally needle-shaped pulses.

[0177] The desired information is encoded with the temporal position of the eight needle-shaped pulses which correspond to the data symbols and which follow each start symbol before a new start symbol is generated. In the exemplary embodiment illustrated, each of the eight needle-shaped pulses lies at one of 128 encodable time positions. This results, as shown in FIG. 11c, in a temporal variation of the modulation pattern according to the data to be transmitted. The start symbol differs from the data symbols in order that it is recognizable particularly easily. There are various possibilities for this. According to FIG. 11a, a pulse that is stronger than the pulses of the data symbols is used for the start symbol. Such an encoding is referred to as bilevel encoding. According to FIG. 11b, a double pulse constructed from two needle pulses that are very close together temporally is used instead. The temporal spacing of the pulse peaks of the double pulse that are very close together is so short that it does not appear in the rest of the data word. The temporal spacing of the double peaks is thus smaller than the shortest time spacing of the 128 encodable time positions.

[0178] It should be pointed out that the start symbols do not just serve for identifying a new data word. Rather, a synchronization can also be derived from the temporal sequence of the start symbol pulses, i.e., at the active counterpart station 3 it is possible to determine how long the base station 2 requires for transmitting a complete data word, and from that it is possible to derive the duration of the time intervals between the 128 time positions encoded in accordance with the protocol. In this case, the synchronization can be effected for instance—assuming corresponding computing power in the active counterpart station 3—by way of autocorrelation with respect to the time spacing of the start symbol pulses.

[0179] Furthermore, for better utilization of the radiation power of the beam transmitting element and thus in order to increase the achievable range, it can be preferred for the start symbols not to be bilevel-encoded, i.e., not to be transmitted with a distinguishable amplitude in comparison with the data pulses, nor for double pulses to be transmitted at the beginning of a data word. Furthermore, specific start pulses could even be completely omitted. In such cases, it is possible to use e.g., brute force decoding by means of checksums or soft decoding or autocorrelation with the use of fixed time spacings of the data words for synchronization purposes.

[0180] FIG. 11c shows a sequence of a plurality of different angle-encoded data words 15 which respectively encode the rotation angle positions ψ.sub.n−1 to ψ.sub.n+2 which were detected at the points in time of the start pulses.

[0181] The data protocol allows a sufficiently rapid and disturbance-free data transmission by way of the modulation of the emitted radiation. In one practical embodiment, it was possible, for instance, to transmit a data word 15 as described within 2.5 μs. This allows a sufficiently frequent transmission of current rotation angle information and/or auxiliary information.

[0182] It should be pointed out that with the transmission method described, latency problems in the transmission between base station and active counterpart station become practically insignificant. Although there can be a temporal delay between the detection of a specific rotation angle position by the angle decoder in the base station 2 and the modulation of corresponding information onto the emitted radiation, this latency occurs within the base station and will moreover be very constant over time to a good approximation—that is to say, for instance, disregarding temperature effects, which can however be reduced by temperature regulation. In this respect, this transmission differs from a communication of current angle information by way of other communication paths such as Wi-Fi, for instance, because latencies can vary greatly in that case. The data transmission described is therefore particularly advantageous, which also applies to base stations according to the prior art with a non-wobbling beam plane.

[0183] A so-called pulse position modulation (PPM) is employed in the implementation described above. It shall be disclosed that further modulation methods such as are known per se from the prior art would be applicable besides such a PPM modulation. In particular, the usability of Manchester encoding, and of the PSK, QPSK, QAM modulation methods, shall be explicitly disclosed, without restriction.

[0184] The measurement accuracy can then be increased with the transmission of the angle encoder data by means of the modulation described. As mentioned above, it takes a certain time until the wobbling beam plane has completely swept over the receiver in the active counterpart station 3, since the beam plane has a finite thickness and the receiver has a finite extent. The alignment of the wobbling beam plane also changes during this duration. It is therefore proposed to increase the measurement accuracy by determination of the temporal centroid of the sweeping-over interval and an interpolation of the angle information—which was obtained during the sweeping-over interval by way of the modulated received radiation—with respect to the temporal centroid.

[0185] It should be noted here that the power received at the receiver of the active counterpart station 3 will vary during the sweeping over. This is readily explicable just from the fact that the complete area of the receiver is impinged on by the beam plane only for a part of the sweeping-over interval, while a part of the receiver is not impinged on by the beam plane at the beginning and end of the sweeping over. Such effects result in the presence of an envelope 47 that varies the received power, such as is illustrated by way of example in FIG. 11d.

[0186] For the interpolation of the angle information, that is to say the accurate determination of a phase angle in the movement cycle of the beam plane normal, it is necessary firstly to determine the temporal centroid of said envelope. For said temporal centroid, the relevant angle is then determined by interpolation.

[0187] However, the envelope is itself not available straightforwardly; this is also not absolutely necessary, however, because it is sufficient to consider the heights of the pulse peaks deformed by the curve. In this respect, recourse is thus had to the analog form 46 of the data stream deformed by the envelope. This is possible in a particularly simple manner by defining expedient, low reception power threshold values, upon the exceedance and undershooting of which start and stop times t.sub.start and t.sub.end are respectively determined; cf. FIG. 11d.

[0188] If it were desired thus to determine the temporal centroid between the expedient limits t.sub.start to t.sub.end, the following formula can be used as a discrete approximation:

[00002]$t_c=\frac{{\int }_{t_{\mathrm{start}}}^{t_{\mathrm{end}}}t.Math.P\left(t\right)\mathrm{dt}}{{\int }_{t_{\mathrm{start}}}^{t_{\mathrm{end}}}P\left(t\right)\mathrm{dt}}$

[0189] Although the value of the temporal centroid thus obtained will depend slightly on the data content of the data words, since after all the data content is encoded via the time positions of the needle pulses, nevertheless the temporal centroid determination made possible is still very good.

[0190] In FIG. 11d, the temporal centroid is designated by t.sub.c. Said temporal centroid lies between the points in time t.sub.n and t.sub.n+1, at which points in time those start pulses are received which indicate the beginning of transmission of data words which encode the two transmitted rotation and phase angles ψ.sub.n and ω.sub.n+1 ascertained directly preceding and succeeding the time t.sub.c, respectively.

[0191] With these designations, the interpolated angle that best corresponds to the temporal centroid of the sweeping of the beam plane over the light receiver can be determined in accordance with:

[00003]${\psi }_c={\psi }_n+\frac{{\psi }_{n+1}-{\psi }_n}{t_{n+1}-t_n}.Math.\left(t_c-t_n\right)$

[0192] This rotation angle can then subsequently be used for the calculation of a direction angle in accordance with the formulae indicated above.

[0193] This procedure can be used to interpolate between the angular steps encoded by the transmitted data words significantly better than with 1/10 of the angular step spacings. Accuracies of better than 2 angular seconds can typically be obtained in this way. In this regard, vertical angle resolutions of 0.17 angular second were achieved in a practical embodiment of a base station 2 whose wobbling beam plane was extended with an aperture angle α (alpha) of +−5°.

[0194] The high accuracies and the simple and thus inexpensive mechanical set-up allow the measuring system disclosed to be used in particular in applications such as road construction and/or for the definition of virtual guide lines.

[0195] In this respect, FIG. 14 shows the attachment of the active targets 3 to a rolling member 69 of a road roller, and to the kinematic center of a screed board 70 of a road paver. The screed board serves to level a hot asphalt pavement 68 with a predetermined height; said predetermined height is intended to be predefined by a virtual guide line.

[0196] In this case, owing to the high precision achieved, upon repeated passages of the road roller over the still hot pavement, the measuring system disclosed above makes it possible to determine the so-called settlement, i.e., to indicate the extent to which the road pavement is compacted by the passages. This in turn makes it possible to indicate directly to the machine operator a measure of the compaction of the road pavement. For this purpose, corresponding output possibilities are provided on the active counterpart station. Preferably, the screed board has attached to it—as illustrated by way of example—at least two active targets or an active counterpart station comprising two receiving stations, which make it possible to determine an absolute height.

[0197] FIG. 15 shows how a virtual string line 64 can be spanned with two base stations 2a and 2b and with a stationary target Rx between the latter. In this case, two virtual planes 65a and 65b are determined for the base station 2a, and two virtual planes 65c and 65d are determined for the base station 2b. In this case, the virtual planes 65b and 65c contain the respective connecting line from the base station 2a and 2b, respectively, to the stationary target Rx arranged therebetween. In order that the virtual planes 65b and 65c are completely defined, a desired direction perpendicular to the connecting lines can additionally be defined. A desired transverse inclination of the virtual planes connecting the base stations and the target situated therebetween is thus defined. On the basis of the virtual planes, it is then possible for an interpolated area to be defined or a virtual guide line to be defined. With the active target 3 arranged in stationary fashion, i.e., the active counterpart station 3 arranged in stationary fashion, it is thus possible to provide a support point for the interpolated areas or guide lines which is set up significantly more simply and is thus less expensive than a base station, specifically even with the use of base stations according to the invention with a wobbling beam plane.

[0198] For road construction 67 with a road paver 61 and with an active target 3 attached to the screed board thereof, FIG. 16 shows in plan view that and how a virtual guide line 64 set up according to the invention using active counterpart stations Rx as support points can be used for height and location determination. It should be mentioned that if additional items of information such as points of intersection of direction angles with the planned course of the travel of the vehicle are incorporated or odometer values are computed with them, it is possible to dispense with an optional absolute position determination at least for the height monitoring, although the necessary control parameters for interpolation and smoothing of the guidance variable at the transition points of the segments are nevertheless determinable sufficiently accurately.

[0199] Although it has been explicitly described above that and how the measuring assembly of the present invention is applicable for guiding vehicles and machines, it should be emphasized that the measuring assembly also affords advantages for a number of further applications.

[0200] In this regard, inter alia, dual-slope lasers for construction site operation can be replaced by the measuring assembly. In this case, it is particularly advantageous to predefine the inclination of the virtual laser plane at the active target and to be able to set the inclination axes with the active target also as desired.

[0201] It is moreover even conceivable for different users here to work with different inclination planes. An application in the leveling of conical surfaces, such as e.g., for conical piles of material, is likewise possible, which otherwise necessitates expensive special lasers.

[0202] Mention should also be made of the possibility, in a manner similar to that in the case of multi-cross lasers, of projecting a plurality of virtual planes that are perpendicular to one another and of aligning them with the active target, without the base station having to be rotated mechanically. These properties are likewise very advantageous for industrial measurement in the case of the alignment of machines and shafts.

[0203] The measuring assembly can furthermore advantageously serve for internal location monitoring of segments in tunnel boring machines or as a core component for innovative canal construction lasers, and also for deformation measurements in monitoring applications.

[0204] A description has thus been given of, inter alia, a measuring assembly for position determination which consists of at least one object whose position or location is to be determined, at least one active target which is spatially fixedly related thereto, and at least one base station, the active target falling within the detection region thereof, and is characterized in that the base station generates a wobbling beam plane and the wobble movement is defined by the fact that the normal to the beam plane rotates about a rotational axis with a rotation angle known at any time, said rotational axis being non-parallel to said normal and being at a predefined, largely constant angle of inclination with respect to said normal, and that the beam plane impinges on the active target at least twice per rotation of the normal.

[0205] Furthermore, a corresponding measuring assembly has been disclosed wherein the at least two angular positions of the rotation of the normal to the beam plane about the rotational axis at the points in time of the two hits are used to calculate at least one direction angle in relation to the polar coordinate system of the base station.

[0206] Furthermore, a corresponding measuring assembly has been disclosed wherein the active target is designed for calculating at least one vertical angle in relation to the polar coordinate system of the base station.

[0207] Furthermore, a corresponding measuring assembly has been disclosed wherein the active target is designed for calculating at least one horizontal angle in relation to the polar coordinate system of the base station.

[0208] Furthermore, a corresponding measuring assembly has been disclosed wherein the base station contains a rotating beam deflecting component.

[0209] Furthermore, a corresponding measuring assembly has been disclosed wherein the base station contains a beam plane expanding component.

[0210] Furthermore, a corresponding measuring assembly has been disclosed wherein the base station contains an optoelectronic beam transmitting element, the radiation of which is collimated and is deflected by the rotating beam deflecting component and is expanded by the beam plane expanding component to form the wobbling beam plane.

[0211] Furthermore, a corresponding measuring assembly has been disclosed wherein a means for modulating the optoelectronic beam transmitting element with an angle-encoded data signal is provided in the base station.

[0212] Furthermore, a corresponding measuring assembly has been disclosed wherein further auxiliary data are also transmitted in addition to the angle data.

[0213] Furthermore, a corresponding measuring assembly has been disclosed wherein the transmitted auxiliary data include the position of an inclination compensator in the base station.

[0214] Furthermore, a corresponding measuring assembly has been disclosed wherein the transmitted auxiliary data include a unique identifier (ID or serial number) of the base station.

[0215] Furthermore, a corresponding measuring assembly has been disclosed wherein the active target is equipped to determine the angular position of the rotation of the normal to the beam plane about the rotational axis from the radiation of the beam plane, said radiation being modulated with the angle-encoded data signal and auxiliary data, at the point in time of the impingement and a temporal centroid calculation.

[0216] A description has also been given of a method for determining height and location of a vehicle by means of a measuring assembly for optical or quasi-optical position determination comprising at least one active target that is fixedly related to the vehicle, and at least one base station, the active target falling within the detection region of said at least one base station, wherein at least one further, stationary, active target is provided, and the connecting line between the base station and the stationary active target spans a segment of a virtual guide wire and a virtual plane with a predefined transverse inclination, at which the vehicle is guided in terms of its working height, in a manner comparable to a traditional guide wire, with the aid of the direction angles of the base station that are obtained by means of the active targets.

[0217] It is advantageous, in the case of such a method for determining the height and location of a vehicle, if a plurality of alternating segments consisting of base stations and stationary active targets form a chain of segments of a virtual guide wire.

[0218] It should be mentioned that it is furthermore advantageous if additional items of information such as points of intersection of the direction angles with the planned course of the travel of the vehicle are incorporated or odometers are computed in order to determine necessary control parameters for interpolation and smoothing of the guidance variable at the transition points of the segments.

[0219] It should be pointed out that the text above mentions at many points a base station that generates a wobbling beam plane, wherein the wobble movement is defined by the fact that the normal to the beam plane rotates about a rotational axis with a rotation angle known at any time, said rotational axis being non-parallel to said normal and being at a predefined, largely constant angle of inclination with respect to said normal, and that the beam plane impinges on the active target at least twice per rotation of the normal. Such a wobble movement generated by rotation of the normal to the beam plane is particularly advantageous because it can be generated and detected in a simple way, as evident above. It should be pointed out, however, that optionally other movements would be possible, for example by virtue of the fact that an optical element used for beam tilting, such as a conical mirror or a planoconcave axicon, does not simply rotate about an axis parallel to the axis of the incident beam, rather a more complex movement is superimposed. By way of example, a normal rotation as described above can be combined with an additional tilting brought about in an actuator-based manner. In this respect, the precession of a gyroscope should be recalled, which likewise need not be totally regular.

[0220] It should be emphasized, however, that specific information can also be transmitted in some other way, for example via radio or in a wired manner. If angle information is transmitted in this case, it is advantageous, however, if the latency is accurately known.