JP2806451B2 - Wave height measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wave height measuring method for measuring a wave height distribution of a wave generated around a hull during navigation.

[0002]

2. Description of the Related Art Waves are generated around a hull during navigation, and when the waves break (break), a crushing sound is generated. This crushing noise has an adverse effect on the detection of schools of fish on fishing boats and the research activities of oceanographic research vessels. For this reason, it is necessary to actually sail the ship to find out how much breaking waves are generated where and how much noise is generated. For that purpose, waves generated around the actual ship must be measured simply and with sufficient accuracy.

[0003] There are the following methods for measuring the wave height.

(1) A method in which a needle is brought into contact with the surface of the water and the needle is followed according to a change in a wave, and the change is detected as a change in electric resistance (servo wave height meter).

(2) A method of analyzing a change in a wave by measuring a time from irradiating an electromagnetic wave or an ultrasonic wave to the water surface until receiving the reflected wave.

(3) A method of analyzing a single image obtained by photographing a marker (a checkered plate) with a camera.

(4) A method of analyzing two images obtained by simultaneously photographing the water surface with two cameras (stereo photography).

[0008]

However, the above-mentioned methods (1) and (2) have the following problems.

The method (1) is a contact type, so that when measuring the wave height on the actual sea surface, it is not possible to measure a position away from the hull. Further, it is difficult to perform multi-point measurement at the same time, and cannot be applied to an unsteady wavefront.

The method (2) is a non-contact method, but it is usually difficult to measure a position far from the hull because the measurable distance is short. In addition, a device capable of measuring a long distance is large-scale and expensive. Furthermore, simultaneous multipoint measurement and measurement of unsteady wavefronts are difficult.

The method (3) can measure a position relatively far from the hull, but its accuracy is not good in principle. Also, it is difficult to simultaneously measure a wide range of the wavefront.

The method (4) can measure a position far from the hull, but requires a special photographing device and an analyzing device and is very expensive. Usually, it is necessary to print the measurement scale in the screen.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a wave height measuring method which can relatively easily and with sufficient accuracy measure a wave height distribution of waves generated around a hull during navigation. It is in.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a wave height measuring method for measuring the wave height distribution of waves generated around a hull during navigation. At least two cameras are installed on the hull to capture the calibration grid from different positions, and the cameras are simultaneously photographed with the calibration grid, and the obtained image of each point of the calibration grid is obtained. After collating and analyzing the above position information, the test grid is removed from the hull, and a specific point on the sea surface is obtained from at least two images of the sea surface taken by the camera during navigation, and obtained by the test grid. The position of the specific point is calculated three-dimensionally from the position information on the image.

A verification grid with a known position is attached to the side wall of the hull in advance, and at least two cameras are installed at different positions on the hull. When the test grids are simultaneously photographed by the cameras, the intersections of one test grid are scattered as point images at different coordinate positions on at least two images. By comparing these images, a conversion formula (matrix) for calculating the three-dimensional position of an arbitrary point image is obtained. After removing the calibration grid from the hull, the ship sails on the actual sea surface, and each camera simultaneously photographs the same sea surface. A wavefront-like common specific point in each captured image is extracted, and the coordinates of the specific point in each image are obtained. By calculating the product of the calculated coordinate matrix and the conversion formula, a matrix representing the three-dimensional position of the specific point is obtained, and the wave height distribution around the hull can be measured relatively easily and with sufficient accuracy.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the measurement principle of the present invention will be described.

When an arbitrary point P (x, y, z) in a three-dimensional space as shown in FIG. 2 is photographed by a camera (not shown) installed at a different position, FIGS.
An image as shown in (b) is obtained. Figure 3 video points on the image shown that in (a) and P _a, the image points on the image shown that in FIG. 3 (b) and P _b.

[0018] The measured values of the point image P _a of the image and L _a, H _a, measured value L _b of the image of the point image P _b, and H _b, the image on the P _a, measured position P _b Values (L _a , H _a ), (L _b , H _b )
Is represented by a first-order linear combination of coordinate values (x, y, z) in a three-dimensional space. That is, _Equations 1 to 4 are assumed with C _ij as a constant.

[0019]

[Number 1] _{H a = C 11 · x +} C 12 · y + C 13 · Z + C 14

[0020]

[Equation 2] L _a = C ₂₁ · x + C ₂₂ · y + C ₂₃ · Z + C ₂₄

[0021]

[Equation 3] H _b = C ₃₁ · x + C ₃₂ · y + C ₃₃ · Z + C ₃₄

[0022]

L _b = C ₄₁ × x + C ₄₂ × y + C ₄₃ × Z + C ₄₄ Four points (x ₁ , x ₁₎ whose coordinates in the three-dimensional space are known
_{y 1, z 1), (} x 2, y 2, z 2), (x 3, y 3, z 3),
(X ₄ , y ₄ , z ₄ ) is represented by Equations 5 to 8.

[0023]

Equation 5] _{H as = C 11 · x s} + C 12 · y s + C 13 · z s + C 14

[0024]

[6] _{L as = C 21 · x s} + C 22 · y s + C 23 · z s + C 24

[0025]

Equation 7] _{H bs = C 31 · x s} + C 32 · y s + C 33 · z s + C 34

[0026]

Equation 8] where _{L bs = C 41 · x s} + C 42 · y s + C 43 · z s + C 44, by simultaneous equations s = 1, 2, 3, 4 equations 1 8 thereof, 16 yuan A system of linear equations is obtained, which can be represented by a matrix as shown in Equation 9.

[0027]

(Equation 9)

By solving equation 9, the matrix C _ij is obtained.

[0029] To determine the position of an arbitrary point in the three-dimensional space, the point _{T (x T, y T,} z T) for H _aT from two images with the same camera, L _aT, H _bT, among L _bT What is necessary is just to measure at least three persons. The number 11 (conversion equation) is obtained by solving this if for example the number 10 a relationship _{of, H aT, L aT, H} bT, 3 person point by substituting this conversion formula of L _bT T coordinates _{(x T, y T, z} T) is obtained.

[0030]

(Equation 10)

[0031]

[Equation 11]

FIGS. 4 (a) and 4 (b) are images obtained by photographing the test grid arranged on the starboard side of the hull model while the ship is stopped with cameras arranged at different positions.

As shown in FIGS. 4A and 4B,
On the starboard side of the hull model 2 placed in the empty circulating water tank 1,
At each intersection of a frame 5 composed of a copper pipe 3 and a thread 4, a jungle gym-shaped test grid 7 in which a large number of bead balls 6 are fixed is arranged. The test grid 7 is used for photographing a group of beads 6 whose positions are known in advance and using them for analysis.
On the starboard side of the hull model 2, two cameras (not shown) are installed at different positions in the height direction. After the test grid is photographed by the camera, the two images are abutted and measured at the coordinates of the position of an arbitrary bead ball 6 on the image to obtain C _ij .

Next, after removing the test grid 7, the circulation water tank 1
Is filled with water, a wave is generated by a wave-making device (not shown), and the hull model 2 is brought into a navigating state, and the water surface is simultaneously photographed by two cameras. FIG. 5A and FIG. 5B are images obtained by photographing the starboard water surface of the hull model 2 during navigation with each camera.

In order to clarify the measurement points on the water surface, a polka-dot-shaped light beam is provided from an observation window on the bottom of the circulating water tank 1 (a film having a plurality of holes formed in the observation window, and a light source is transmitted through the film. 8) were irradiated upward. further,
Fine bubbles were flowed from the upstream to promote diffuse reflection on the water surface, making it easier to observe.

The wave height was measured by calculating the positions of the common specific points 8a to 8n on the water surface in three dimensions, respectively, using the conversion equation (Equation 11) obtained in advance.

FIG. 6 is a three-dimensional diagram of a wavefront based on data obtained by calculating the position of a common specific point from the position information of the images of two cameras using a conversion formula. As shown in the figure, it can be seen that the height of the wave at a position away from the hull is shown three-dimensionally.

Thus, the wave height distribution around the hull can be measured relatively easily and with sufficient accuracy.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1A and 1B are views showing one embodiment of the wave height measuring method of the present invention.

As shown in FIG. 1 (a), the stopped ship 10
A verification grid 11 is mounted on the starboard side so as to include the waterline 12, and the two cameras 13 and 14 are installed so that the verification grid 11 can be photographed at different positions vertically (or left and right). The test grid 11 is photographed by the two cameras 13 and 14 at the same time, the obtained images of the two cameras 13 and 14 are compared, and the coordinates of the point image of the common grid point on the images are measured. A conversion formula for calculating the dimension position is obtained.

Next, the test grid 11 is removed from the hull 10,
The hull 10 is made to sail (FIG. 1B). The same sea surface is photographed simultaneously with the two cameras 13 and 14 while the hull 10 is being navigated. By comparing the obtained two images of the sea surface and calculating the three-dimensional position of the coordinates of the specific point on the wavefront using a conversion formula, the wave height distribution around the hull can be measured relatively easily and with sufficient accuracy. Can be.

In the above, the wave height measuring method of the present embodiment does not require a special camera, unlike the stereo photographing method used for creating a topographic map. It is not necessary to precisely measure the positional relationship of the cameras used for measurement in the present embodiment, so that the measurement system can be easily installed. If a TV (television) camera is used as a camera, an unsteady wavefront can be continuously measured. By accurately measuring the position of the test grid, practically sufficient measurement accuracy can be obtained.

In the present embodiment, the case where two cameras are used has been described. However, three or more cameras may be used at the same time, and in this case, the measurement range can be expanded and the measurement accuracy can be improved.

[0045]

In summary, according to the present invention, the following excellent effects are exhibited.

A verification grid is attached to the side wall of the hull,
After photographing the test grid from different positions, collating and analyzing the position information on the obtained image of each point of the test grid,
The test grid is removed from the hull, a common specific point on the sea surface is determined from at least two images of the sea surface taken by the camera during navigation, and the position of the specific point is determined in three dimensions from the position information obtained by the test grid. Since the calculation is performed, the wave height distribution of the waves generated around the hull during navigation can be measured relatively easily and with sufficient accuracy.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing an embodiment of a wave height measuring method according to the present invention.

FIG. 2 is a diagram showing coordinates in a three-dimensional space.

FIGS. 3A and 3B are images obtained by photographing an arbitrary point P in a three-dimensional space with cameras installed at different positions.

4 (a) and 4 (b) are images obtained by photographing a test grid arranged on the starboard side of a hull model at a standstill with cameras arranged at different positions. FIG.

FIGS. 5 (a) and (b) are images obtained by photographing the starboard water surface of a hull model during navigation with each camera.

FIG. 6 is a three-dimensional diagram based on data obtained by calculating a position of a common specific point from a position information of images of two cameras using a conversion formula.

[Explanation of symbols]

 10 Hull 11 Calibration grid 13,14 Camera

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-53-120488 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01C 13/00 G01C 11/00-11 / 34

Claims (1)

(57) [Claims] 1. A wave height measuring method for measuring a wave height distribution of a wave generated around a hull during navigation, wherein a calibration grid having a number of points whose positions are known in advance is attached to a side wall of the hull.
After installing at least two cameras on the hull for photographing the test grid from different positions, photographing the test grid simultaneously with each camera, collating and analyzing the obtained positional information on the image of each point of the test grid, Removing the test grid from the hull and determining a common specific point on the sea surface from at least two sea surface images taken by the camera during navigation;
A wave height measuring method characterized by calculating a position of a specific point in three dimensions from position information on an image obtained by the test grid.