WO1995010051A1 - Equipment for calibration of navigation aids - Google Patents

Equipment for calibration of navigation aids Download PDF

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Publication number
WO1995010051A1
WO1995010051A1 PCT/NO1994/000162 NO9400162W WO9510051A1 WO 1995010051 A1 WO1995010051 A1 WO 1995010051A1 NO 9400162 W NO9400162 W NO 9400162W WO 9510051 A1 WO9510051 A1 WO 9510051A1
Authority
WO
WIPO (PCT)
Prior art keywords
equipment
calibration
accuracy
navigation
navigation aids
Prior art date
Application number
PCT/NO1994/000162
Other languages
French (fr)
Inventor
Petter Fergestad
Lars Furuseth
Original Assignee
Scan-Tech A/S
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
Priority claimed from NO933583A external-priority patent/NO933583D0/en
Application filed by Scan-Tech A/S filed Critical Scan-Tech A/S
Priority to AU79510/94A priority Critical patent/AU7951094A/en
Publication of WO1995010051A1 publication Critical patent/WO1995010051A1/en

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
    • G01S3/02—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 radio waves
    • G01S3/023—Monitoring or calibrating
    • 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
    • G01S1/00—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
    • G01S1/02—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using radio waves
    • G01S1/022—Means for monitoring or calibrating

Definitions

  • the invention concerns a method for calibration of navigation aids for aviation comprising recording from aircraft of signals transmitted by such navigation aids compared with position reports from one or more alternative reference systems with the object of measuring and evaluating the accuracy of the aircraft's position as indicated by the navigation aids.
  • the most critical of aviation navigation aids is radio-based instrument landing systems, with the technical designation ILS, MLS and Marker beacons, and radio-based en route navigation systems with the technical designation VOR, DME, NDB and TACAN.
  • visual aids such as, e.g., VASIS and radar-based aids such as, e.g. SSR.
  • the International Civil Aviation Organization (ICAO) requires that countries which place navigation aids at the disposal of international aviation should routinely calibrate these aids in order to contribute to the safety of aircraft movements.
  • calibration of such navigation aids involves measuring and evaluating the accuracy of navigation aids when indicating the position of aircraft using them.
  • the method according to the invention is primarily directed towards the radio-based navigation aids since these are the most critical. However, equipment according to the invention can also be employed in calibrating other navigation aids such as those mentioned above.
  • the method according to the invention enables equipment for calibration of radio- based navigation aids to be produced wherein such calibration can be performed with greater accuracy and at a lower cost than in previously known equipment.
  • the equipment according to the invention is also lower in weight and has less volume than known equipment for calibration purposes as described, and the equipment according to the invention can thereby be used in smaller aircraft, which further reduces the cost of implementing calibration according to the invention.
  • Navigation receivers which are employed in known calibration equipment use analog filters in order to filter out those frequency components which are bearers of the relevant information content and rectify these signals. The result of this processing is then input by known equipment for calibration and subjected to further analog and/or digital processing.
  • the described preliminary analog filtering and rectification which are performed in the navigation receivers constitute the weakest link in the chain of elements which determine the accuracy of known calibration equipment, since, amongst other things, analog filters contain mechanical components which are sensitive to temperature variations and mechanical vibrations.
  • Laboratory equipment with greater accuracy than the above-described calibration equipment is further known, such equipment being used amongst other things for laboratory calibration of calibration equipment as described.
  • measuring equipment is not nearly fast enough to be used as airborne calibration equipment and is therefore not a real alternative to the described known calibration equipment.
  • the object of the present invention is to provide a method for calibration of navigation aids for aviation which overcomes the described weaknesses in the known equipment for such calibration, thus enabling calibration to be performed with improved accuracy and at a lower cost.
  • the object of the invention is achieved with a method and equipment which are characterized by the features in the patent claims presented.
  • VOR/ILS systems can be measured with an accuracy which is better than 20% +/- 0.8% for individual degree of modulation and with a phase resolution which is equal to or better than 0.001 degrees.
  • DDM measurements can be made with an error which is less than or equal to 0.0002 DDM for ILS localizers and less than or equal to 0.0005 DDM for ILS glidepaths.
  • Fig. 1 illustrates the simultaneous use of a theodolite and navigation aids in order to register the aircraft's position. Readings are taken of the aircraft's position according to the signals of the navigation aids from the airborne calibration equipment which simultaneously also receives, e.g. via telemetry, a position report as observed from the theodolite operator. By comparing these two positions the accuracy of the navigation aids can be evaluated.
  • the shown position determination by means of theodolite can also be performed on a more up to date basis by means of satellite-based navigation systems such as Differential GPS, or also with radar, laser-based, infrared signals/sensors or other suitable reference systems.
  • Fig. 2 illustrates the fundamental design of the equipment according to the invention.
  • the equipment consists of a high-speed primary part I, and a high-precision calibration part II. Both the primary part and the high-precision part of the calibration equipment receive their power supply via an inverter 1 which converts the aircraft's 28 V direct current supply to 220 V alternating current.
  • the signals from the navigation aids are received in the equipment's navigation receivers 3 & 4 via navigation antennae 2 mounted on the aircraft.
  • the outputs therefrom, mixed down to intermediate frequency level, are assigned in the primary part of the equipment to analog filtering and digitalizing 5, and in the high-precision part to sampling/digitalizing 6.
  • the digitalized signals from the two parallel systems are further processed in a signal processor 7, where the high-precision signals are used for continuous calibration of the primary part before the precision-adjusted signal is compared with the position report from the reference system in a PC controller 8 before storing and presentation 9. If differential satellite navigation is used as a reference system, there are also required a GPS receiver with telemetry receiver 10 and antennae 11 for reception of satellite signals and for reception of correction signals from the permanently located satellite receiver according to the prior art. If a theodolite is used, the satellite receivers are not required.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Traffic Control Systems (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)
  • Navigation (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Abstract

A method for calibration of navigation aids for aviation is described. The method comprises recording from aircraft of radio signals transmitted from such navigation aids and comparison with position reports from one or more alternative reference systems. The aircraft's primary equipment (I) is calibrated continuously with parallel-running separate high-precision digital equipment (II) which from the intermediate frequency (IF) signal level (6) exclusively employs digital signal processing with an accuracy of at least 16 bits.

Description

Equipment for calibration of navigation aids
The invention concerns a method for calibration of navigation aids for aviation comprising recording from aircraft of signals transmitted by such navigation aids compared with position reports from one or more alternative reference systems with the object of measuring and evaluating the accuracy of the aircraft's position as indicated by the navigation aids.
The most critical of aviation navigation aids is radio-based instrument landing systems, with the technical designation ILS, MLS and Marker beacons, and radio-based en route navigation systems with the technical designation VOR, DME, NDB and TACAN. In addition to this there are visual aids such as, e.g., VASIS and radar-based aids such as, e.g. SSR. The International Civil Aviation Organization (ICAO) requires that countries which place navigation aids at the disposal of international aviation should routinely calibrate these aids in order to contribute to the safety of aircraft movements.
In the method according to the invention calibration of such navigation aids involves measuring and evaluating the accuracy of navigation aids when indicating the position of aircraft using them.
The method according to the invention is primarily directed towards the radio-based navigation aids since these are the most critical. However, equipment according to the invention can also be employed in calibrating other navigation aids such as those mentioned above.
The method according to the invention enables equipment for calibration of radio- based navigation aids to be produced wherein such calibration can be performed with greater accuracy and at a lower cost than in previously known equipment.
The weakness of known equipment for such calibration is that it is based on the same components and the same technology for signal filtering as the equipment used by aircraft for determining their position. Known equipment for calibration of navigation aids is therefore subject to the same sources of error and has the same limitations with regard to accuracy as the equipment employed by users of navigation aids, such accuracy being affected by the mechanical vibrations and temperature variations which will always exist on board the aircraft on which the calibration equipment is located. It is a known procedure to perform regular calibration of the above-mentioned known calibration equipment in a laboratory on the ground in order to ensure as far as possible maximum accuracy during the measurements. However, it will be understood that due to the said equipment sensitivity to temperature variations and mechanical vibrations such laboratory calibration will not be capable of ensuring the continuous quality of the airborne equipment's measurement results when it really counts, i.e. in the air during the measurements concerned.
Since the method according to the invention is based on completely different components and a completely different technology, a substantially greater accuracy can be obtained with equipment according to the invention than that achieved by the users of navigation aids. This is a normal requirement in connection with calibration in general, but it has not been attainable with known equipment.
The equipment according to the invention is also lower in weight and has less volume than known equipment for calibration purposes as described, and the equipment according to the invention can thereby be used in smaller aircraft, which further reduces the cost of implementing calibration according to the invention.
It is known in the art to perform regular calibration of equipment and instruments with the object of checking whether their accuracy remains within specified limits. Such calibration should be performed with substantially greater accuracy, normally around 10 times better, than that which is indicated for the equipment which is calibrated.
It is also known in the art to perform the calibration described here for navigation aids for aviation. This is implemented by means of recording from aircraft signals transmitted by navigation aids and comparing the resulting position report with the position report from reference systems. This is carried out with a frequency in the order of 10 times per second.
Known equipment for such calibration receives its navigation signals from the same types of navigation receivers as aircraft themselves use and thus known calibration equipment is not capable of introducing an accuracy level for the calibration which is in accordance with the generally accepted requirements for a substantial increase in accuracy as described above.
Navigation receivers which are employed in known calibration equipment use analog filters in order to filter out those frequency components which are bearers of the relevant information content and rectify these signals. The result of this processing is then input by known equipment for calibration and subjected to further analog and/or digital processing. The described preliminary analog filtering and rectification which are performed in the navigation receivers constitute the weakest link in the chain of elements which determine the accuracy of known calibration equipment, since, amongst other things, analog filters contain mechanical components which are sensitive to temperature variations and mechanical vibrations.
Laboratory equipment with greater accuracy than the above-described calibration equipment is further known, such equipment being used amongst other things for laboratory calibration of calibration equipment as described. However, such measuring equipment is not nearly fast enough to be used as airborne calibration equipment and is therefore not a real alternative to the described known calibration equipment.
An example of such laboratory equipment is equipment which is based on a purely digital data acquisition and processing from intermediate frequency level in order to avoid the use of analog filters. If this technology is to have the necessary accuracy for the present purpose (16 bits), considerable processing time will be required and it will thereby be too slow to be a direct alternative to existing flight calibration equipment.
Today's frontline equipment in the field can only perform a few calculations per second with the necessary accuracy (16 bits).
The object of the present invention is to provide a method for calibration of navigation aids for aviation which overcomes the described weaknesses in the known equipment for such calibration, thus enabling calibration to be performed with improved accuracy and at a lower cost. The object of the invention is achieved with a method and equipment which are characterized by the features in the patent claims presented.
The above-mentioned objects are achieved with a method according to the invention which is characterized by the combination of the best features of two technologies: known technology for calibration equipment, with its advantage of speed, is combined with known technology for digital data acquisition and processing, with its advantage of accuracy. The result can be described as flight calibration equipment which is continuously calibrated (several times per second) during the measuring process. It can also be described as calibration equipment which utilizes high-precision digital data acquisition and processing in order to perform a small number of measurements per second, while the remaining intermediate interpolation is performed by means of known flight calibration technology. By means of this combination solution a substantial improvement in the accuracy is obtained by using equipment in a moderate price class within each of the fields concerned. It was only when newly-developed signal processing technology came into use that it was possible to perform such digital processing with a sufficiently high degree of accuracy and simultaneously at a sufficiently high speed to enable it to be employed for continuous calibration of the primary system according to the method according to the invention. The technology as described in principle in, e.g., US patent 4.768.035 (approximately 50 dB/8 bits) will not be nearly accurate enough to fulfil the specific requirements placed on a flight calibration system. In this context the requirements are at least 16 bits accuracy with 100 kHz sampling frequency and a further processing which enables the aircraft's position to be updated at least once per second. Only when these requirements are simultaneously fulfilled will a substantial improvement in the equipment's accuracy, stability and signal/noise ratio be achieved compared with previously known equipment.
With this technology it is possible to calibrate continuously from once to five times per second.
It is foreseen that some time in the future digital technology will be further developed to a level where it will be sufficiently fast and accurate to enable it to be entirely based on digital data acquisition and signal processing. When that time comes, this system will, of course, be used and parallel systems like that described here will no longer be employed.
As practical examples of the accuracy which is achieved with a method and equipment according to the invention, VOR/ILS systems can be measured with an accuracy which is better than 20% +/- 0.8% for individual degree of modulation and with a phase resolution which is equal to or better than 0.001 degrees. DDM measurements can be made with an error which is less than or equal to 0.0002 DDM for ILS localizers and less than or equal to 0.0005 DDM for ILS glidepaths.
The object and advantages of the method according to the invention will be better understood from the following description taken in conjunction with the figures.
Fig. 1 illustrates the simultaneous use of a theodolite and navigation aids in order to register the aircraft's position. Readings are taken of the aircraft's position according to the signals of the navigation aids from the airborne calibration equipment which simultaneously also receives, e.g. via telemetry, a position report as observed from the theodolite operator. By comparing these two positions the accuracy of the navigation aids can be evaluated. The shown position determination by means of theodolite can also be performed on a more up to date basis by means of satellite-based navigation systems such as Differential GPS, or also with radar, laser-based, infrared signals/sensors or other suitable reference systems.
Fig. 2 illustrates the fundamental design of the equipment according to the invention. The equipment consists of a high-speed primary part I, and a high-precision calibration part II. Both the primary part and the high-precision part of the calibration equipment receive their power supply via an inverter 1 which converts the aircraft's 28 V direct current supply to 220 V alternating current. The signals from the navigation aids are received in the equipment's navigation receivers 3 & 4 via navigation antennae 2 mounted on the aircraft. The outputs therefrom, mixed down to intermediate frequency level, are assigned in the primary part of the equipment to analog filtering and digitalizing 5, and in the high-precision part to sampling/digitalizing 6. The digitalized signals from the two parallel systems are further processed in a signal processor 7, where the high-precision signals are used for continuous calibration of the primary part before the precision-adjusted signal is compared with the position report from the reference system in a PC controller 8 before storing and presentation 9. If differential satellite navigation is used as a reference system, there are also required a GPS receiver with telemetry receiver 10 and antennae 11 for reception of satellite signals and for reception of correction signals from the permanently located satellite receiver according to the prior art. If a theodolite is used, the satellite receivers are not required.

Claims

PATENT CLAIMS
1. A method for calibration of navigation aids for aviation comprising recording from aircraft radio signals transmitted by such navigation aids, comparing the resulting position fixing for the aircraft with a position fixing from one or more reference systems with the object of establishing the quality of the navigation signals and the accuracy of the aircraft's position as indicated by the navigation aids, ch a ra cterized in that high-speed primary equipment (I) is calibrated continuously with parallel-running separate high precision digital equipment (II) which from intermediate frequency (IF) signal level (6) exclusively employs digital signal processing with an accuracy of at least 16 bits.
2. A method according to claim 1 , ch a racterized in that the high-speed primary equipment (I) is calibrated at least once per second with parallel-running separate high-precision digital equipment (II).
3. An apparatus for calibration of navigation aids for aviation consisting of a power supply (1), navigation receivers (3 & 4) with antennae (2), theodolite with telemetry or other reference sensors such as, e.g., GPS/DGPS (10 & 11) together with primary calibration equipment (I), ch a racterized in that high-precision calibration equipment (II) consisting of a PC controller (8), a unit for data acquisition (6) with an accuracy of at least 16 bits and a sampling frequency of at least 100 kHz and a unit for signal processing (7) which together enable the primary equipment (I) to be calibrated at least once per second and presentation of results (9).
PCT/NO1994/000162 1993-10-07 1994-10-06 Equipment for calibration of navigation aids WO1995010051A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU79510/94A AU7951094A (en) 1993-10-07 1994-10-06 Equipment for calibration of navigation aids

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
NO933583A NO933583D0 (en) 1993-10-07 1993-10-07 EQUIPMENT FOR CALIBRATION OF NAVIGATION AID
NO933583 1993-10-07
NO941860A NO179090C (en) 1993-10-07 1994-05-18 Equipment for calibration of navigational aids
NO941860 1994-05-18

Publications (1)

Publication Number Publication Date
WO1995010051A1 true WO1995010051A1 (en) 1995-04-13

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PCT/NO1994/000162 WO1995010051A1 (en) 1993-10-07 1994-10-06 Equipment for calibration of navigation aids

Country Status (3)

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AU (1) AU7951094A (en)
NO (1) NO179090C (en)
WO (1) WO1995010051A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107091651A (en) * 2017-06-29 2017-08-25 飞智控（天津）科技有限公司 Navigation module alignment aid and calibration method
US10823580B2 (en) 2018-01-19 2020-11-03 Honeywell International Inc. Inspection of a navigation aid

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111983550B (en) * 2020-08-27 2024-04-12 航天科工微电子系统研究院有限公司 GPS-based radio direction finding precision testing method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3999859A (en) * 1974-08-06 1976-12-28 Societe Anonyme De Telecommunications Device for checking radio aerial navigational aids
US5056051A (en) * 1989-06-06 1991-10-08 Technology For Communications International Signal direction finding processor using fast Fourier transforms for receiver matching
US5248973A (en) * 1991-10-24 1993-09-28 The Mitre Corporation High-speed, high-resolution analog to digital converter subranging architecture
GB2272343A (en) * 1992-11-10 1994-05-11 Gec Ferranti Defence Syst Automatic aircraft landing system calibration

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3999859A (en) * 1974-08-06 1976-12-28 Societe Anonyme De Telecommunications Device for checking radio aerial navigational aids
US5056051A (en) * 1989-06-06 1991-10-08 Technology For Communications International Signal direction finding processor using fast Fourier transforms for receiver matching
US5248973A (en) * 1991-10-24 1993-09-28 The Mitre Corporation High-speed, high-resolution analog to digital converter subranging architecture
GB2272343A (en) * 1992-11-10 1994-05-11 Gec Ferranti Defence Syst Automatic aircraft landing system calibration

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107091651A (en) * 2017-06-29 2017-08-25 飞智控（天津）科技有限公司 Navigation module alignment aid and calibration method
CN107091651B (en) * 2017-06-29 2023-12-26 一飞(海南)科技有限公司 Navigation module calibration auxiliary device and calibration method
US10823580B2 (en) 2018-01-19 2020-11-03 Honeywell International Inc. Inspection of a navigation aid

Also Published As

Publication number Publication date
NO179090C (en) 1997-08-19
AU7951094A (en) 1995-05-01
NO941860L (en) 1995-04-10
NO179090B (en) 1996-04-22
NO941860D0 (en) 1994-05-18

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