JPH1123350A - Method and apparatus for measuring liquid level - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly grasp a liquid level and a state of the liquid level simultaneously by dividing periodically obtained liquid level data to groups by a standard deviation value, analyzing the data of each group and obtaining the liquid level as well as a cycle and an amplitude of waves. SOLUTION: Images picked up by a camera are collected and precisely measured at an image-processing means, thereby obtaining liquid level data. The liquid level data are analyzed to obtain characteristics of waves (an amplitude and a cycle). Specifically, a two-dimensional space constituted of a time (t) and a water level height (y) of time series data are divided to Ai-Hi groups (i=1, 2... n) on the basis of an average value (m) and a variance σ calculated from the time series data of a suitable range. The wave amplitude is obtained, e.g. from a maximum value of the C1 group and a minimum value of the G1 group. The wave cycle is calculated by evaluating a presence probability of necessary and sufficient data, giving a priority order, calculating, e.g. the A1 group and E1 group first and A1 , A2 groups next if the A1 , A2 groups have better data. The analysis result is transmitted to a data-processing computer together with a measurement result of a liquid level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the level of water in rivers and lakes, the level of tide in the sea and the like, and the level of liquid such as oil (hereinafter collectively referred to as "liquid level") and changes in the level of liquid. In other words, the present invention relates to a liquid level measuring method and apparatus for detecting a wave cycle and an amplitude, and in particular, measures a liquid level standing on a river or the like from a remote place using a camera or the like, measures the liquid level by image processing, and measures the liquid level. The present invention relates to a liquid level measuring method and apparatus suitable for automatically measuring the period and amplitude of a wave with high accuracy.

[0002]

2. Description of the Related Art A conventional liquid level measuring technique installed in a river or the like will be described with reference to FIG. FIG. 11 is an explanatory diagram of a float type water level measurement device. The water level measurement device
Usually, it is installed, for example, every 1 km along the flow of the river. In the water level measuring device shown in FIG.
2, the observation well 32 and the river water 39 are communicated with each other by the horizontal water pipe 34, the float 33 is floated in the observation well 32, and the position of the float 33 is adjusted using the weight 35, the pulley 36, the rope 38, and the like. The float measurement position is set as the water level of the river 39. In this float type water level measuring device, if the tip end 40 of the horizontal water pipe 34 is clogged with gravel or the like due to flooding or the like, the water level of the river 39 cannot be measured. In addition to 32, a normal vertical water mark 37 is installed on the river bank, and the communication level of the water pipe 34 is checked by periodically comparing the water level checked on the scale with the measured value at the observation well 32. In addition, it is very difficult to control the gravel or the like from clogging the horizontal water pipe tip 40.

As another conventional technique, there is an ultrasonic water level measuring device for detecting a water level in a non-contact manner. In this ultrasonic type, since the transmission characteristics of the ultrasonic wave change depending on the temperature, temperature correction is essential, and the ultrasonic wave emitted from the transmitter / receiver to the water surface is reflected on the water surface, and the reflected wave is transmitted / received by the transmitter / receiver. When receiving the wave and obtaining the water surface position 5 from the reflected wave data, the water surface measurement position is corrected based on the temperature measured by the thermometer.

The conventional liquid level measuring method is described in, for example, Mechanical Engineering Handbook (Revised 6th edition; Japan Society of Mechanical Engineers 197).
7; Part 6 Measurement method Chapter 7, 7.6 “Measurement of liquid level”).

[0005]

In order to measure the liquid level with high accuracy, it is inevitable to detect even a small change in the liquid level. In other words, if it is not possible to detect even one wave up and down, the liquid level is not measured with high accuracy. For this reason, a high-precision liquid level measuring device must also be able to measure the period and amplitude of the detected wave. However, FIG.
As shown in Fig. 1, a conventional liquid level measuring device draws water from a river or the like into an observation well and measures the liquid level in the observation well. There is a problem that can not be. Further, since the float is floated and the liquid level is observed from the vertical movement of the float, there is also a problem that a change in wave cannot be detected with high accuracy due to the inertial mass of the float. The ultrasonic type liquid level measuring device does not have high accuracy per se, and cannot detect changes in waves with high accuracy.

[0006] The inventor of the present application has taken a technique of imaging a liquid level portion in contact with a water mark standing on a river or the like with a camera, analyzing the captured image using image processing technology, and measuring the liquid level with high accuracy. (Japanese Patent Application Laid-Open Nos. 7-333039 and 8-
No. 14992, JP-A-8-145765, Japanese Patent Application No. 7-1995.
323220). The liquid level measurement technique based on this image processing makes it possible to finely measure the liquid level that rises and falls by a wave by shortening the measurement cycle, that is, the capture cycle of a still image, and obtaining the liquid level in each still image. However, waves in rivers and seas are not regular, unlike electric waves, and easily break due to wind, so even if conventional waveform analysis technology is applied to measured liquid level data, There is a problem that it is difficult to determine the wave period and amplitude with high accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid level measuring method and a liquid level measuring apparatus capable of measuring a fine change of a liquid level, that is, a change of a wave with high accuracy and also measuring a cycle and amplitude of a wave with high accuracy. .

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid level measurement method in which a liquid level in contact with a liquid surface is periodically imaged and a liquid level in a captured image is determined by image processing. This is achieved by obtaining an average value and a standard deviation of the data, dividing the liquid level data into groups according to the value of the standard deviation, analyzing the data of each group and obtaining the period and amplitude of the wave on the liquid surface. You.

[0009] By grouping the time series data (liquid level data) of the liquid level at the fixed point according to the average value and the standard deviation, it is possible to easily determine the period even for the wave whose waveform is broken. Become.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a liquid level measuring device according to an embodiment of the present invention. This liquid level measuring device includes a water mark 1, an imaging means 4 such as a camera, and a processing device 13 for performing data processing such as image processing.

The water mark 1 is installed at a liquid level measuring place such as a river, and has two columns 1a and 1b which are set up almost vertically at the installation location, and between the columns 1a and 1b. It is composed of a plurality of inclined plates 1c that are fixed in parallel and in multiple stages. Prop 1a, 1b of water mark 1 formed in this ladder shape
The width between them is, for example, about 1 m, and a scale is provided on each inclined plate (water-distribution plate) 1c corresponding to the rung of the ladder. Note that this scale may be omitted. Inclined plate 1c
It is preferable to have a structure that can be exchangeably attached to the pillars 1a and 1b, since the soil is dirty by being immersed in muddy water such as a river or exposed to direct sunlight for a long time.

A camera 4 for picking up an image of a portion of the water mark 1 in contact with the liquid level, which is installed at the liquid level measuring location, is provided with a preset head 12.
It is installed on the upper part, and the direction of the camera 4 can be adjusted according to the liquid level. When the camera 4 is installed outdoors, the camera 4 is stored in the camera housing 11. In this embodiment, a camera 4 (head 12) is provided on a camera pole 15 installed outdoors. Then, a camera attitude control device 16 is provided, and the camera attitude control device 16 receives an instruction from the processing device 13 and controls the attitude of the camera 4 (head 12). The camera 4 may be used also as a surveillance camera currently used for another purpose, or a dedicated camera may be newly installed. The camera installation location is not limited to the camera pole 15,
It may be installed on a structure such as a building.

The processing device 13 is composed of a measuring device main unit 17 and a data processing unit 18. The measuring instrument body 17 is
An image processing unit 2 for capturing and processing the captured image of the camera 4 and an image recording unit 10 for storing the processed image are provided. The image processing unit 2 also outputs a signal for instructing the camera attitude control device 16 to instruct the attitude of the camera 4. Provide functions. The data processing unit 18 includes a data processing computer 3 that processes output data of the image processing unit 5, a printer 5, and a plotter 6.
And display means 7.

The image recording means 10 records the image picked up by the camera 4 as evidence data 14 on the tape 9 as it is. For example, using a VTR tape for home use, one year of camera images (still images) captured in units of several minutes are recorded on one tape for permanent storage, for tracking missing data and correcting erroneous data. Can be used as The data processing unit 3 outputs a report 8 of the measured water level and a characteristic value 19 of the wave. FIG. 2 is a diagram illustrating the principle of measuring the liquid level using the inclined plate 1c. In FIG.
Reference numeral 21 denotes a reflection image formed by reflecting the real image portion 20 c (the portion on the liquid surface) on the liquid surface 23. Since the real image portion 20 is inclined, the bent portion, that is, the liquid level position can be easily detected from the captured images of the images 20 and 21. FIG. 2A shows a case where the liquid surface is specularly reflected. However, in a state where there is no reflection and the liquid is transparent, as shown in FIG. Is observed as Also in this case, the bent portion, that is, the liquid level plate can be easily detected from the captured images of the real image 20 and the refraction image 22. FIG. 2C shows a state in which no reflected image or refracted image is observed, and shows a case in which only the real image section 20 is imaged. In this case, the liquid level position can be recognized most. Actually, an image is captured in a state where the three states in FIG. 2 are mixed, but the liquid level is easily recognized because the water level plate is provided diagonally.

The value of the recognized liquid level may be read by a scale mark provided on the inclined plate 1c (real image 20), but the scale mark is contaminated with mud or the like or exposed to direct sunlight. When the measurement can be performed only by relying on the scale, the measurement cannot be performed. Therefore, the characteristic portion of the real image 20 of FIG. 2A, for example, the tip portion is recognized by image recognition, and the value of the liquid level is obtained from the positional relationship between the tip portion and the liquid level. The water mark 1 shown in FIG. 1 shows five inclined plates 1c, and the camera 4
Can be obtained from the posture of

FIG. 3 is a diagram showing processing functions in the image processing means 2 shown in FIG. In the process 24 for measuring the liquid level, an image is captured in step A100,
In step A200, the measurement position of the liquid surface is obtained, and
In step 300, the measurement result is stored in the storage device 25, and step A
At 400, it is determined whether or not the processing has been completed. If the processing has not been completed, the process returns to step A100, and image capture is performed again. For example, when precise measurement is performed at an interval of 0.1 second every hour, this time-series liquid level measurement data is stored in the storage device 25.
Is stored in The image processing means 2 transmits the measurement result of the liquid level to the data processing computer 3 by the function 26, and analyzes the liquid level data measured precisely by the function 27 to obtain the characteristic of the wave as described later in detail. This analysis result is transmitted to the data processing computer 3.

FIG. 4 is a flowchart showing a processing procedure for obtaining the wave characteristics. First, in step C100, data in an appropriate range is extracted from the time-series data, and the average value m and the variance σ are calculated. Next, based on the mean value m and the variance σ, the two-dimensional space in which the time-series data exists (the space formed by the time t and the water surface height y) is divided into groups as shown in FIG. Are made to belong to one of the groups (step C200). And
Using the data grouped in this way, the cycle of the wave is calculated as described later in detail (step C30).
0). Then, in the next step C400, the amplitude of the wave is calculated. The amplitude of this wave is the maximum of the Ci group and G
It can be obtained from the minimum value of the i group. The value of the cycle and the amplitude of the wave thus obtained is transmitted to the data processing computer 3 (step C500).

FIGS. 5 to 9 are flowcharts showing the detailed procedure of step C300 in FIG. 4, that is, the procedure for measuring the wave period. First, the grouped data is evaluated (Step C300-10), and a calculation procedure suitable for the feature is selected (Step C300-20). If appropriate data exists in the Ai group and the Ei group,
In step C300-30, the cycle of the wave is calculated. If better data exists in the Ai group and the Ai + 1 group, the cycle of the wave is calculated in step C300-40. If appropriate data exists in the Ci group and the Gi group, the cycle of the wave is calculated in steps C300-50. Further, when appropriate data exists in the Ci group and the Ci + 1 group, the cycle of the wave is calculated in steps C300-600. Before choosing which of these steps to choose, prioritize each step and evaluate if there is enough data in the group used to perform that step. Select that step. If the data is not sufficient, the same evaluation is performed for the next higher priority step. If the data is sufficient, the step is selected. If the data is not sufficient, the process proceeds to the next step. This is repeated to select an optimal step.

FIG. 6 is a flowchart showing a detailed procedure of steps C300-30. The Ai group has y =
This is a data group in the vicinity of m. If this approximate straight line is created, the intersection of this approximate straight line and y = m becomes the origin of the wave. The procedure for creating an approximate straight line in step C300-30-20 is as follows.

A data group belonging to the Ai group is represented by (t
(1), y (1)), (t (2), y (2)), ..., (t
(K), y (k)), the approximate straight line is given by the following equation 1.

[0021]

(Equation 1)

The intersection Ti between y = at + b and y = m is
Next number 2

[0023]

## EQU2 ## Ti = (mb) / a is obtained by the formula (Step C300-30-30).

For the data in the Ei group, an approximate straight line is obtained in the same manner as described above (steps C300-30-40 and steps C300-30-50), and the intersection coordinates T 'are obtained. Then, according to the following equation 3, the period of the wave is

[0025]

Calculate the period ΔT = (Ti′−Ti) × 2.

FIG. 7 is a flowchart showing the detailed procedure of step C300-40 in FIG. 5, and shows a case where the wave cycle is measured using the data group of the Ai group and the data group of the Ai + 1 group. The basic processing is shown in FIG.
Since it can be understood in the same way as in the case of, the description is omitted.

FIG. 8 is a flowchart showing the detailed procedure of step C300-50 in FIG. 5, and shows a case where the wave cycle is measured using the data group of the Ci group and the data group of the Gi group. In this step C300-50, the data group median value of the Ci group is measured and set as Thi (step C300-50-20). The center position may be determined using an appropriate method. For example, the data may be arranged in ascending order to take a central value, or an average may be obtained from the leftmost data and the rightmost data. On the other hand, the data group median value of the Gi group is measured and set as Thi '(step C300-50-30). And the following equation 4

[0028]

## EQU4 ## The period can be obtained from the period ΔT = (Ti′−Ti) × 2 (step C300-5)
0-40).

FIG. 9 is a flowchart showing the detailed procedure of step C300-50 in FIG. 5, and shows a case where the wave cycle is measured using the data group of the Ci group and the data group of the Ci + 1 group. The basic concept of this processing is the same as that of FIG. 8, and a description thereof will be omitted.

[0030]

According to the present invention, the following effects can be obtained. 1) The liquid level of the liquid where the wave is generated cannot be accurately grasped without simultaneously measuring the characteristics of the wave on the surface of the liquid, but in the present invention, the period and amplitude of the wave together with the liquid level are simultaneously measured. As a result, the state of the liquid level can be accurately grasped. 2) Even if the waveform is broken, the wave period can be measured reliably.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a liquid level measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a basic principle of measuring a liquid level by image processing using an inclined plate.

FIG. 3 is an explanatory diagram of a processing concept of a measurement period main unit shown in FIG. 1;

FIG. 4 is a flowchart showing a processing procedure of the characteristic measurement of the wave shown in FIG. 3;

FIG. 5 is a flowchart showing a detailed procedure of Step C300 shown in FIG. 4;

FIG. 6 is a flowchart showing a detailed procedure of Step C300-30 shown in FIG. 5;

FIG. 7 is a flowchart showing a detailed procedure of Step C300-40 shown in FIG. 5;

8 is a flowchart showing a detailed procedure of Step C300-50 shown in FIG.

FIG. 9 is a flowchart showing a detailed procedure of Step C300-60 shown in FIG. 5;

FIG. 10 is a diagram showing a method of grouping a two-dimensional space where data exists (time t and water surface height y) by an average value m and a standard deviation σ.

[Explanation of symbols]

1 ... water mark, 2 ... measuring instrument main unit, 3 ... data management unit, 4
... Camera, 23 ... Liquid level, 19 ... Wave characteristic output report.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 2, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a liquid level measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a basic principle of measuring a liquid level by image processing using an inclined plate.

FIG. 3 is an explanatory diagram of a processing concept of a measurement period main unit shown in FIG. 1;

FIG. 4 is a flowchart showing a processing procedure of the characteristic measurement of the wave shown in FIG. 3;

FIG. 5 is a flowchart showing a detailed procedure of Step C300 shown in FIG. 4;

FIG. 6 is a flowchart showing a detailed procedure of Step C300-30 shown in FIG. 5;

FIG. 7 is a flowchart showing a detailed procedure of Step C300-40 shown in FIG. 5;

8 is a flowchart showing a detailed procedure of Step C300-50 shown in FIG.

FIG. 9 is a flowchart showing a detailed procedure of Step C300-60 shown in FIG. 5;

FIG. 10 is a diagram showing a method of grouping a two-dimensional space where data exists (time t and water surface height y) by an average value m and a standard deviation σ.

FIG. 11 is an explanatory diagram of a conventional float type water level measuring device.

[Description of Signs] 1 ... Water mark, 2 ... Measuring instrument main unit, 3 ... Data management unit, 4
... Camera, 23 ... Liquid level, 19 ... Wave characteristic output report.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Norio Murayama, Inventor 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Process Computer Engineering Co., Ltd. (72) Inventor Hiroshi Suzuki 5-chome, Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi Process Computer Engineering Co., Ltd. (72) Inventor Mikio Yoda 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Inside Omika Plant, Hitachi, Ltd.

Claims (2)

[Claims] In a liquid level measuring method for periodically capturing a water mark in contact with a liquid surface and determining a liquid level in a captured image by image processing, an average value and a standard deviation of liquid level data obtained in each cycle. The liquid level data is divided into groups by the value of the standard deviation, and the data of each group is analyzed to determine the period and amplitude of the wave on the liquid level. 2. A liquid level measuring apparatus which periodically captures a water mark in contact with a liquid surface and obtains a liquid level in a captured image by image processing, wherein an average value and a standard deviation of liquid level data obtained in each cycle are provided. , A means for grouping the liquid level data according to the value of the standard deviation, and a means for analyzing the data of each group to determine the period and amplitude of the wave on the liquid surface. Liquid level measuring device.