WO2014202049A1 - Procédé servant à déterminer une vitesse optimale du son dans l'eau, et dispositif servant à mettre en œuvre ledit procédé - Google Patents

Procédé servant à déterminer une vitesse optimale du son dans l'eau, et dispositif servant à mettre en œuvre ledit procédé Download PDF

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Publication number
WO2014202049A1
WO2014202049A1 PCT/DE2014/100175 DE2014100175W WO2014202049A1 WO 2014202049 A1 WO2014202049 A1 WO 2014202049A1 DE 2014100175 W DE2014100175 W DE 2014100175W WO 2014202049 A1 WO2014202049 A1 WO 2014202049A1
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WO
WIPO (PCT)
Prior art keywords
sound velocity
sonar
image
subsonic
determining
Prior art date
Application number
PCT/DE2014/100175
Other languages
German (de)
English (en)
Inventor
Johannes Groen
Abdelhak M. ZOUBIR
Stefan Leier
Original Assignee
Atlas Elektronik Gmbh
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 Atlas Elektronik Gmbh filed Critical Atlas Elektronik Gmbh
Publication of WO2014202049A1 publication Critical patent/WO2014202049A1/fr

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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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52004—Means for 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
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
    • 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
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52003—Techniques for enhancing spatial resolution of targets

Definitions

  • the invention relates to a method for determining an optimal subsonic sound velocity, to a method for focusing a defocused sonar image and to an apparatus for carrying out the method.
  • Underwater sound velocity is generally determined by parameters measured by sensors in the water. Common parameters are in particular pressure, temperature, salinity and flow. On the basis of the underwater sound velocity, in particular the distance to an object can be determined, which was detected by means of a sonar.
  • the parameters determining sensors are regularly local, for example, on an AUV
  • a disadvantage is that changes in the parameters which are present at a certain distance from the sensor can not be measured by the sensors can be determined.
  • SAS Synthetic Aperture Sonar
  • defocused SAS images are corrected by means of fractional lower-order statistics (FLOS-PGA).
  • FLOS-PGA fractional lower-order statistics
  • An optimal speed of sound is estimated by an optimization problem. This is based on the finding that a false speed of sound leads to a quadratic phase error in the synthetic aperture.
  • the autofocusing takes place, in particular, by manipulating the phases in the frequency domain (Wavenumber domain).
  • a particular disadvantage is that the method assumes that there are a number of point targets in the SAS image for autofocusing.
  • the object of the invention is to improve the state of the art.
  • the object is achieved by a method for determining an optimal subsonic sound velocity, the method comprising the following steps:
  • the present optimal subsonic sound velocity is a good estimate of a true subsonic sound velocity, since changes in parameters such as temperature, pressure or salinity along the propagation are unimportant - especially through "averaging" - and are covered by the optimum subsonic sound velocity obtained.
  • the "underwater sound velocity” includes the propagation velocity of the sound in the medium of water, whereby the water is especially sea or sea water or even fresh water.
  • An “optimal subsonic sound velocity” (hereinafter also referred to as Co) includes a value that takes into account all the influences of the medium: While the underwater sound may have different velocities in its propagation path, the optimum subsonic sound velocity describes an average velocity over the entire course time the sound wave.
  • the "first underwater sound velocity” includes a first suspected or sensor-determined underwater sound velocity Although ideally the first subsonic sound velocity is equal to the optimal underwater sound velocity, but in
  • the first subsonic sound velocity has an Ac error, resulting in a "smeared” sonar image.
  • the "second subsonic sound velocity" has a different value than the first one
  • the second subsonic sound velocity differs by 1m / s to 3m / s, with larger or smaller values may be possible and useful.
  • a "sonar signal” includes any signals from a sonar.
  • Radar data represent in particular any electronic signals and representations of a sonar signal during or after receiving the sonar signal.
  • signals of the hydrophones are included as well as already prepared (eg through sample-and-hold circuits) signals.
  • the delimitation of the raw data is to be seen in particular to sonar image data, which are already processed and their quality measure can be determined.
  • a "sonar image” is generally an electronic representation of a reality under water
  • SAS image is generated in particular on the basis of transmitted and received underwater sound signals.
  • the first sonar image corresponds to a representation of reality using the first subsonic sound velocity and the raw data and the second sonar image representative of the reality using the second subsonic sound velocity and the identical raw data.
  • a "measure of quality” is in particular a (numerical) value, which reflects a statement about the quality of displayed objects.
  • the quality measure is often determined by means of metrics.
  • Point spread function or point spreading function called Point spread function or point spreading function called.
  • Other metrics / quality measures can be found in the article Leier et al. "SEQUENTIAL FOCUS EVALUATION OF SYNTHETIC APERTURE SONAR IMAGES” (IEEE ICASSP Conference Proceedings, May 26-31, 2013, Vancouver, Canada), the content of which is part of the present application, which can measure the quality of the entire sonar image as well be determined only on the basis of subareas of the sonar image.
  • a very primitive measure of quality can be a line-based and / or column-based
  • a contrast can be determined as an intensity transition from one pixel to the next adjacent one.
  • the "first and second quality measure” are the comparable values / functions to the respective sonar images.
  • the “best quality measure” is that which has the highest or correspondingly lowest value - in other words the best sonar image.
  • the reflected signals received by the receiving arrangement (SAS antenna) having the number L u of antenna elements (receiving elements within a receiver array of the sonar antenna) at the airtime index p can be described by Formula (2).
  • the Lauzeitverzögerung is also called two-way runtime of the transmission signal.
  • a u describes the spatial distance between the individual
  • Co is the true speed of sound in the medium.
  • a homogeneous medium is assumed. Assuming exact motion information, such as an AUV and thus the transmit / receive antenna, and replacing the necessary
  • Micronavigation in the form of a DPCA (displaced phase center antenna) algorithm (a micronavigation is performed ⁇ ⁇ ⁇ * -.)
  • a SAS image can be '* directly using, for example, a
  • ⁇ ⁇ is the carrier frequency, the distance-focused reflection signals and ⁇ ( ⁇ ) an indicator function [see in particular Leier et al. "SEQUENTIAL FOCUS EVALUATION OF SYNTHETIC APERTURE SONAR IMAGES” (IEEE ICASSP Conference Proceedings, May 26-31, 2013, Vancouver, Canada)]. The latter describes whether a grid point g k i is transmitted through the transmitter or the receiver "Seen” or “illuminated”. It should be noted,
  • the focusing delay ' '; ⁇ ' ⁇ ⁇ reconstruction in formula (4) is identical to the propagation delay of the formula (3), wherein which can be adopted not necessarily at lattice imperfections, as may arise deviations due to a lattice mismatch despite correct underwater sound speed.
  • phase center approximation a transmitter-receiver pair is replaced by a virtual transceiver, which is located in the (virtual) geometric center between transmitter and receiver.
  • additional sonar images are obtained using the raw data and additional subsonic sound velocity and the associated additional quality measures, and all quality measures are compared.
  • the sonar image can be selected with the best quality measure and thus a better value for the
  • Underwater sound velocity can be determined.
  • Quality measure leads directly to a lower value for the underwater sound velocity can be used. In this example, there is a change of direction.
  • Real time in this case means in particular that in the time interval between the determination of two SAS images, the optimum subsonic sound velocity can be determined.
  • the determination of the quality measures / metrics can be parallelized. The actual comparison of the quality measures can then be processed by a single processor.
  • the process can be carried out online or offline.
  • the sonar images or raw data are processed after the mission or with a time delay to record the data, so that a map with exact distances and proportions can be provided, in particular after measurement using a sonar.
  • the object is achieved by a method for focusing a defocused sonar image, wherein the optimal
  • Underwater sound velocity determined in accordance with a method described above and the associated sonar image to the optimal subsonic sound velocity can be determined.
  • sonar images of higher quality and / or sharper contours can be provided.
  • focused representation is to be understood as an optimal representation of the sonar image.
  • a "defocused” is especially when sonar images show objects that are "out of focus”.
  • the object is achieved by a device which is set up such that one of the methods described above can be carried out.
  • Figure 1 is a highly schematic representation of different sonar images with different quality measures.
  • AUV Autonomous Underwater Vehicle
  • SAS Synthetic Aperture Sonar
  • the SAS determines raw data. Furthermore, the AUV measures water pressure, temperature and salinity using attached sensors. Based on the sensor data, a first "estimate" of the subsonic sound velocity is calculated. Alternatively, the speed of sound is measured directly by means of a sonic velocity sensor.
  • the calculated (measured) value of the subsonic sound velocity is 1500 m / s.
  • a step 1 the first SAS image is determined with this first subsonic sound velocity [see Fig. Id.]].
  • the determined subsonic sound velocity is increased to 1502.5 m / s and also a SAS image (here the second SAS image [see Fig. Le.]]).
  • a possible contrast measurement for an overall image is: [54]
  • PSF metrics are determined.
  • the underwater sound velocity is reduced again in step 3 and set to the value 1495 m / s.
  • the associated SAS image lb.) and the associated contrast value m c are determined and compared with the values for the SAS image lc.). Since the contrast value m c has improved, in step 4 the subsonic sound velocity is set to the value of 1492.5 m / s and the associated SAS image 1 a) and the associated contrast value m c are determined.
  • the contrast value m c has deteriorated from the contrast value m c of the SAS image lb.), so it is assumed that the SAS image lb.) has the best quality and that the best description for the underwater sound velocity is 1495 m / s is.

Landscapes

  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

Abstract

L'invention concerne un procédé servant à déterminer une vitesse optimale du son dans l'eau. Ledit procédé comprend les étapes qui suivent consistant à : - déterminer des données brutes d'un signal sonar ; - déterminer une première image sonar en utilisant les données brutes et une première vitesse du son dans l'eau ; - déterminer une deuxième image sonar en utilisant les données brutes et une deuxième vitesse du son dans l'eau ; - déterminer une première mesure de qualité de la première image sonar et une deuxième mesure de qualité de la deuxième image sonar et comparer la première mesure de qualité à la deuxième mesure de qualité ; et - sélectionner la vitesse du son dans l'eau, qui relève de l'image sonar dotée de la meilleure mesure de qualité, ladite vitesse du son dans l'eau sélectionnée correspondant à la vitesse optimale du son dans l'eau.
PCT/DE2014/100175 2013-06-18 2014-05-21 Procédé servant à déterminer une vitesse optimale du son dans l'eau, et dispositif servant à mettre en œuvre ledit procédé WO2014202049A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102013106359.4 2013-06-18
DE201310106359 DE102013106359A1 (de) 2013-06-18 2013-06-18 Verfahren zum Bestimmen einer optimalen Unterwasserschallgeschwindigkeit sowie Vorrichtung zum Durchführen des Verfahrens

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CN105004413B (zh) * 2015-06-11 2018-01-05 华南理工大学 用于水下目标定位的声传播路径综合速度测定方法与装置

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HANSEN ET AL.: "The effect of sound velocity variations on synthetic aperture sonar", PROC. UNDERWATER ACOUST MEAS. (UAM, 2007
LEIER ET AL.: "SEQUENTIAL FO US EVALUATION OF SYNTHETIC APERTURE SONAR IMAGES", IEEE ICASSP CONFERENCE PROCEEDINGS, 26 May 2013 (2013-05-26)
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112526454A (zh) * 2020-10-22 2021-03-19 自然资源部第一海洋研究所 一种顾及表层声速和坐标先验信息的水下控制点定位方法
CN112526454B (zh) * 2020-10-22 2022-04-26 自然资源部第一海洋研究所 一种顾及表层声速和坐标先验信息的水下控制点定位方法

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