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WO1988009480A1 - Procede et dispositif pour compenser l'effet de turbulence en geodesie - Google Patents

Procede et dispositif pour compenser l'effet de turbulence en geodesie Download PDF

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Publication number
WO1988009480A1
WO1988009480A1 PCT/CH1988/000093 CH8800093W WO8809480A1 WO 1988009480 A1 WO1988009480 A1 WO 1988009480A1 CH 8800093 W CH8800093 W CH 8800093W WO 8809480 A1 WO8809480 A1 WO 8809480A1
Authority
WO
WIPO (PCT)
Prior art keywords
target point
frequencies
measuring
different
measuring device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/CH1988/000093
Other languages
German (de)
English (en)
Inventor
Bernhard Gaechter
André HUISER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Leica Geosystems AG
Original Assignee
Wild Heerbrugg AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wild Heerbrugg AG filed Critical Wild Heerbrugg AG
Publication of WO1988009480A1 publication Critical patent/WO1988009480A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
    • G01S3/782—Systems for determining direction or deviation from predetermined direction
    • G01S3/783—Systems for determining direction or deviation from predetermined direction using amplitude comparison of signals derived from static detectors or detector systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C15/00—Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
    • G01C15/002—Active optical surveying means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
    • G01S3/781—Details

Definitions

  • the invention relates to a method for compensating for inhomogeneities in the refractive index of a dispersive medium when determining the direction of a target point by evaluating the propagation behavior of wave radiation emanating from the target point, according to the preamble of patent claim 1 of the procedure.
  • This basic knowledge leads to the object of the present invention, which consists in developing a method and a device for detecting and compensating for such turbulence effects when determining the direction, so that even variable inhomogeneities for a short time in the refractive index of a dispersive medium when determining the direction of a target point by evaluating the propagation behavior of a wave radiation emanating from the target point.
  • the measures according to the invention offer significant advantages in several respects: Even in the event of strong turbulence in the medium along the measuring path between the measuring point and the target point, e.g. perform very precise corrected angle measurements within seconds. The effects of turbulence are recorded briefly and also simultaneously with the actual measurement and processed to a corrected measured value. The reproducible accuracy of the measured values is a few hundred nanoradians when the measuring time of a few seconds is selected.
  • Fig. 4 shows the example of a transmitter with a laser diode for generating two transmission frequencies
  • Fig. 5 shows a receiver circuit for the invention
  • FIG. 1 There is a direct geometric connection D between a transmitter 1 and a receiver 2. Light rays emanating from the transmitter 1 are deflected along the transmission path as a result of changes in refractive index, so that they are in the receiver at an angle ⁇ with respect to the straight line D arrive. Without a correction, the transmitter 1 would be a virtual transmitter l r appear on the connection D ', which can lead to incorrect measurements, in particular in the case of angle measurements and measurement methods based thereon.
  • the dispersion effect is used, by means of which two different frequencies B and R are deflected to different extents along the transmission path.
  • the difference in the angle of incidence caused by the dispersion is delta ⁇ . It has now been shown that, due to the dispersion, the angle difference delta ⁇ is, in a first approximation, directly proportional to the angle error ⁇ originating from the changes in the refractive index.
  • the method described in more detail below takes this knowledge into account in that the angle deviations delta ⁇ caused by the dispersion are measured in very short time intervals as a series of individual measurements and are averaged over a period of seconds or minutes. The required correction for the actual measured value is then obtained from the mean value obtained. The time intervals mentioned for determining the correction values are matched to the actual changes in the refraction behavior of the transmission medium.
  • n (x, y, z) is the refractive index of the medium (e.g. air)
  • exp (ik (c + ax + by)] represents a plane wave propagating in the direction (a, b, l).
  • the angles a and b are only dependent on the wavelength of the light via the refractive index n, such as this is necessary for the turbulence compensation.
  • FIG. 4 shows the principle of obtaining two transmission frequencies from a single laser diode by frequency doubling.
  • the deflected beam passes through a non-linear crystal 8, e.g. a potassium niobate or lithium niobate crystal.
  • the frequency of the light wave is doubled, in the example to 860 nm.
  • This frequency lies in the blue range and is designated B in FIG. 4, in contrast to the original frequency, which is in red -Range and is designated with R.
  • an intensity filter 9 is provided in at least one of the beam paths.
  • a rotating chopper disk 10 which carries out a different intensity modulation for both frequencies. This is achieved by slits S1 and S2 of different widths on the circumference of the chopper disk 10.
  • the light rays R and B emanating from the transmitter 1 of different frequencies are collected jointly by a receiver optics 5 and directed onto the surface of a position-sensitive detector 6.
  • the different frequencies are red and blue light beams which emanate from at least one laser diode in the transmitter.
  • the detector is, for example, a dual photodiode, which has two adjacent light-sensitive areas E and F.
  • an evaluation circuit on the receiver side has inputs E and F for the output signals of the photodiode regions and a reference input Ref.
  • the input signals E and F are each fed to a sample and hold circuit 11 or 12.
  • the outputs of these two circuits are sampled by a multiplex circuit 14, amplified in an amplifier 15 and fed to registers 17 via an analog / digital converter 16, where the signals for further processing in can be temporarily stored in a computer 18.
  • Angular differences delta ß are obtained from the position signals at the inputs E and F.
  • these values are related to other measured values in the sense of a correction in accordance with a predetermined program, so that corrected measured values can be output directly at the computer output, or these values are stored for later processing.
  • two light frequencies of approximately 430 nm and approximately 860 nm were transmitted through an air atmosphere of approximately 24 degrees Celsius.
  • the aperture of the receiver optics was 36 mm in one case and 46 mm in the second case.
  • the individual measured values were averaged after 1 see and after 10 see. The results are as follows:

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Electromagnetism (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

Pour appréhender et compenser l'effet de turbulence lors de mesures directionnelles entre un point visé et une station de mesure, on met on oeuvre un rayonnement avec au moins deux fréquences d'émission. L'angle d'incidence des deux ondes choisies est mesuré à la station de mesure pratiquement simultanément. On détermine ensuite la différence entre les deux angles et on calcule l'écart d'angle entre la direction apparente et la direction réelle à l'aide d'un algorithme approrié. Avec cette méthode, on peut aussi tenir compte d'une inhomogénéité variable et transitoire dans l'indice de réfraction d'un milieu dispersif lors de la détermination de la direction d'un point-cible. Même lors d'une forte turbulence sur la ligne de visée entre le point visé et le point de mesure, on obtient des mesures d'angles avec correction et d'une grande précision en des temps très courts, par exemple de quelques secondes.
PCT/CH1988/000093 1987-05-19 1988-05-19 Procede et dispositif pour compenser l'effet de turbulence en geodesie Ceased WO1988009480A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH1918/87-4 1987-05-19
CH191887A CH674080A5 (fr) 1987-05-19 1987-05-19

Publications (1)

Publication Number Publication Date
WO1988009480A1 true WO1988009480A1 (fr) 1988-12-01

Family

ID=4221623

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CH1988/000093 Ceased WO1988009480A1 (fr) 1987-05-19 1988-05-19 Procede et dispositif pour compenser l'effet de turbulence en geodesie

Country Status (3)

Country Link
CH (1) CH674080A5 (fr)
DE (1) DE3730093A1 (fr)
WO (1) WO1988009480A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE9101398D0 (sv) * 1991-05-08 1991-05-08 Geotronics Ab Kompensationsanordning foer hoejdavstaemnings- instrument

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3369445A (en) * 1963-09-09 1968-02-20 Litton Systems Inc Optical alignment ascertaining device and process for elimination of refractive effects
US3915574A (en) * 1974-09-26 1975-10-28 Rca Corp Method for determining an accurate alignment of a laser beam
DE3130747C1 (de) * 1981-08-04 1983-02-24 Dornier System Gmbh, 7990 Friedrichshafen Verfahren und Vorrichtung zur Bestimmung der Koordinaten des fiktiven Auftreffpunktes von ungebrochenen Lichtstrahlen

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3369445A (en) * 1963-09-09 1968-02-20 Litton Systems Inc Optical alignment ascertaining device and process for elimination of refractive effects
US3915574A (en) * 1974-09-26 1975-10-28 Rca Corp Method for determining an accurate alignment of a laser beam
DE3130747C1 (de) * 1981-08-04 1983-02-24 Dornier System Gmbh, 7990 Friedrichshafen Verfahren und Vorrichtung zur Bestimmung der Koordinaten des fiktiven Auftreffpunktes von ungebrochenen Lichtstrahlen

Also Published As

Publication number Publication date
DE3730093C2 (fr) 1990-07-12
CH674080A5 (fr) 1990-04-30
DE3730093A1 (de) 1988-12-01

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