KR20140073385A - Snow depth measurement method and apparatus - Google Patents

Abstract

A snowfall amount measuring method and a snowfall amount measuring apparatus using a single laser distance meter are provided. A snowfall measuring apparatus according to the present invention includes a laser distance measuring device, a step motor including a rotating shaft, a step motor connected to the step motor by a predetermined angle and connected to a plane perpendicular to the rotating shaft, And a control unit controlling the step motor to control the laser distance measuring unit while rotating the mirror to measure the distance. According to the present invention, since the mirror for reflecting the laser beam is slightly inclined and rotated, it becomes possible to measure the amount of snow on a plurality of points scattered along a circle on the eye surface.

Description

[0001] Snow depth measurement method and apparatus [

The present invention relates to a snowfall measurement method and apparatus, and more particularly, to a method and apparatus for more practical and reliable measurement and calibration of snow depth (snowfall) accumulated on the ground.

With the development of the Internet and communication networks, meteorological data measurement has become more automated by using computers, communication equipment, and sensors.

The measurement of snowfall is one of the interesting areas in the field of automatic measurement because of the importance and necessity of automation, especially when the location of the target location is far from the meteorological center or residential area.

Because of this, many manufacturers have developed snowfall measurement equipment based on a variety of technologies, including laser distance meters, ultrasonic measurements, visual signal (image signal) processing, and mechanical measurement methods.

Snowfall measurement equipment based on currently available or proposed laser distance measurement techniques use one or two lasers and associated receivers (eg, Korean Patent No. 348574). Because of this, complaints are raised regarding inconsistent measurement results and vulnerabilities to various environments in actual measurement sites. For example, if the target point of the laser transmitter is obscured or obstructed by foreign matter such as leaves, dust, or snowflakes flying, the measurement result will not represent the desired information about the snowfall at that point. Also, measuring only one or two points at an area of 3 feet by 3 feet does not represent the total area.

Models based on ultrasound signals are widely used, but these models have weaknesses in terms of measurement accuracy due to the nature of the ultrasound signal itself and variations due to temperature variations.

Some models based on image processing use various signal / image processing techniques to recognize the locations of several points representing the depth of the eye. One of the problems with these models is caused by unclear or fuzzy images due to snow or ice formed at a target point, such as a scaled rod, and a large number of light sources in a straight line. Another minor problem is that if it gets too dark, you have to provide adequate lighting. (E.g. U.S. Patent Application Publication No. 2011/0219868)

Methods based on mechanical measurements have potential problems of mechanical malfunction due to cold weather, strong winds, and the formation of ice. In addition, there is a possibility that the measurement result may vary significantly depending on the type of eye. For example, if the eyes are soft, the eye-contacting mechanism may press the eyes and affect the measurement data.

US Patent No. 6,044,699), or a method of measuring a wide area using a GPS signal (e.g., U.S. Patent No. 5,761,095) using a container, Although there are several studies on these, these methods relate to applications different from those to which the solution provided by the present invention is applied.

In order to solve these problems while maintaining the required accuracy and consistency, a laser distance meter based on a structure having a plurality of laser emitters and receivers may be tried. As would be expected, this method will be more expensive, especially when it is necessary to measure many points to meet the requirements for real-life applications.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a snowfall measuring method and apparatus using a single laser range finder and having less influence of the surrounding environment and high reliability of a measurement result.

The present invention proposes a method for solving the conventional problems by making a multi-point measurement of snowfall using a single laser range finder combined with a rotating mirror. The rotating mirror is slightly inclined so that the reflected laser signal at different time points (rotation angle) points to different points on the circle (ellipse) generated by the laser light projection. This method makes it possible to measure snowfall on a number of points scattered along a circle on the eye surface. The size of the circle (ellipse) may vary depending on the distance of the mirror from the plane perpendicular to the motor axis that rotates the mirror and the tilt angle.

The present invention also provides a method of calibrating a device of the present invention. A box or jig is used to lift the target area by a predetermined height so as to be able to calculate the angle of arrival at each point of the circle on the ground or eye surface in the calibration procedure.

 According to another aspect of the present invention, the proposed method calculates the average depth of the area defined by this circle. Abnormal measurements are discarded and the average is calculated with only meaningful measurement data.

The snowfall measuring apparatus of the present invention includes a laser distance measurer, a target point changing means for changing a distance measurement target point of the laser distance meter, and a control portion for controlling the target point changing means to measure distances at a plurality of target points .

The target point changing means includes a step motor including a rotating shaft, a mirror connected to the step motor at a predetermined angle and connected to a plane perpendicular to the rotating axis, for reflecting the laser beam to / from the laser distance measuring device . The control unit controls the step motor to control the laser distance measuring unit while rotating the mirror to measure the distance.

The controller measures the distance by controlling the laser distance measuring device, repeats the process of rotating the step motor by a predetermined rotation angle ϕ and then measuring the distance until the mirror rotates once, .

Let L ( t ) be the measured distance from the mirror to the surface of the eye at an arbitrary measurement time t , Lg ( t ) be the distance from the mirror to the surface of the eye, and θ ( t ) be the angle between the laser beam and the surface , The snowfall amount d ( t ) at the measurement order t can be obtained by d ( t ) = ( Lg ( t ) - Ls ( t )) x sin θ ( t ).

It is preferable that the control unit calculates an average snowfall amount using only the remaining measurement values by removing a value higher or lower than a certain rate than the average value of the measured snowfall value. The snowfall measuring apparatus of the present invention may further comprise communication means for transmitting the measured distance value to the external apparatus.

The snowfall measuring apparatus of the present invention can be accommodated in a protective cover for protecting the apparatus. The protective cover is provided with a glass in front of the mirror of the snowfall measuring device.

The snowfall measurement method of the present invention is a snowfall measurement method using a snowfall amount measurement apparatus for measuring a snowfall amount on a plurality of points scattered along a circle or an ellipse on an eye surface and measuring a distance from the measurement apparatus to a plurality of points on the circle or ellipse Sequentially measuring the snowfall amount, and calculating a snowfall amount from the plurality of measured distance values.

Let Ls ( t ) be the measurement distance from the measurement device to the surface of the eye at any measurement point t , Lg ( t ) be the distance from the measurement device to the surface, and θ ( t ) be the angle at which the laser beam meets the surface. , The snowfall amount d ( t ) at the measurement point t can be obtained by d ( t ) = ( Lg ( t ) - Ls ( t )) x sin θ ( t ).

When calculating the snowfall amount, it is preferable to calculate the average snowfall amount using only the remaining snowfall value by removing a snowfall amount value which is higher than or lower than a certain rate than the average value of the snowfall amount values at the plurality of measured points.

Sequentially measuring a distance Lg ( t ) to a plurality of points on the surface of the earth corresponding to the plurality of points on the circle or ellipse before the snowfall measuring step; calculating a - sin θ (t) = Lref / (Lr (t) Lg (t)) corresponding to the phase with the plurality points to measure in sequence the distance Lr (t) to the number on the jig surface point corresponding to And performing a calibration process including a step of performing a calibration process.

According to the present invention, since the rotating mirror for reflecting the laser beam is slightly inclined, it becomes possible to measure the amount of snow on a plurality of points scattered along a circle on the eye surface. It is also possible to detect the erroneous measurement data over time and isolate the affected point (s) until the erroneous operation is repaired. In addition, since a larger number of samples can be obtained for a circle (ellipse) shape on the eye surface, the average snowfall measured may be closer to the actual snowfall value as compared to other methods based on one or less samples. In addition, in the present invention, the size of the target area can be easily changed by moving the equipment or changing the tilt angle of the mirror. Further, according to the present invention, only a low-cost device including one laser distance measuring instrument, a step motor and a mirror is used, so that it can be made into a relatively small housing with high cost efficiency and lower complexity.

1 is a conceptual diagram showing a configuration of a snowfall measuring apparatus of the present invention.
2 is an explanatory diagram for explaining a laser beam reflecting operation of the snowfall measuring apparatus of the present invention.
3 is a view for explaining the principle of measurement of snowfall amount of the snowfall amount measuring apparatus of the present invention.
4 is a view for explaining an operation of the snowfall measuring apparatus of the present invention for measuring snowfall along a circle on the snow surface.
5 is an example of a measurement data graph having a projection value and a depression value.
Figure 6 shows three consecutive measurements with anomalies.
Figure 7 shows an example of a jig used for calibration.
8 is a view for explaining a method of performing the calibration of the present invention by using a jig having a height Lref.
9 is a flowchart illustrating a calibration process according to an embodiment of the present invention.
Figure 10 shows an embodiment using an enclosure and glass to protect against wind and dust.

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

In the following description, the "depth" of the eye refers to the height of the eye from the surface of the earth, and the terms "circle" and "ellipse" refer to a pattern formed on the eye surface by laser reflected light reflected by a tilt mirror They are used interchangeably. The amount of movement by the step motor expressed in degrees is expressed as the measurement time (or measurement point) "t" or the rotation angle "φ".

The snowfall measuring system according to an embodiment of the present invention shown in FIG. 1 has the following four components: a laser distance meter module 10, a mirror 11 that tilts from a plane perpendicular to the axis of the step motor A step motor 12 connected to a mirror, and a processing module or computer module 13 as a control unit.

1, the laser beam reflected by the mirror 11, which is tilted and rotated by the step motor 12, is projected on a plane 22 formed by stacked eyes to form an elliptical (or circular) . When the scan is started, the laser distance measuring module 10, by the control of the processing module 13, emits a laser signal and receives the signal reflected from the eye and coming through the mirror 11. The processing module 13 determines the distance from the reference point to a point on the eye surface pointed by the mirror 11 from the received signal and records the data. Then, the processing module 13 outputs a control signal for rotating the step motor 12 by a predetermined rotation angle ϕ and performs laser signal emission, reception, and depth measurement processes for the next position. By repeating this process, an elliptical scan is projected onto the eye.

2 shows how the tilted mirror 11 changes the reflection direction of the laser signal from the laser range finder module 10 as the step motor 12 rotates. 2, since the mirror 11 is connected to the step motor 12 via the shaft 14 in a state of being inclined by an angle? With respect to the plane 15 perpendicular to the shaft 14, When the motor 12 rotates, the tilted angle of the mirror 11 changes, and accordingly, the direction of the light reflected by the mirror 11 also changes.

As shown in Fig. 3, when the measurement distance from the mirror 11 to the surface of the eye at some measurement time point (measurement point) t is Ls ( t ) and the distance from the mirror 11 to the surface is Lg ( t ) , The depth d ( t ) of the eye at the time point t can be obtained by the following equation. Here, θ ( t ) is the angle at which the laser beam meets the ground surface at time t .

d (t) = ((Lg (t) - Ls (t)) x sin θ (t)

The processing module 13 repeats the above steps for the next point on the circle 21. To complete the measurement for all points on the ellipse, the measurement system of the present invention repeats the same steps from t = 0 to t = n-1 until the total angle rotated by the step motor 12 is 360 degrees, Calculate the amount of snowfall for the points. The angles φ of each interval are as follows.

φ = 360 / n

FIG. 4 is a graph showing the positions of the points at φ = 360x (n-1) / n at all points on the circle (ellipse) 21 of the eye surface from t = 0 to t = n- And how the measurements are made. The snow depth (snowfall) d ( t ) at each time t (rotation angle φ) can be obtained as follows.

d ( t ) = ( Lg ( t ) - Ls ( t )) x sin ? ( t )

( t = 0 to n-1, n = number of samples measured along a circle on the target surface above the eye)

Lg ( t ) at each point in time from t = 0 to t = n-1 (360x (n-1) / n degrees from the rotation angle φ = 0 degrees) (for each point on the circle 24 on the earth surface) The measured distance value) and the value of [theta] ( t ) are determined in a calibration procedure, which will be described later.

Once the measurement of one revolution is completed, the processing module 13 may store all measurement data in a local repository or transmit it to an external server via a communication channel for further analysis.

The processing module 13 or the external server analyzes the data by taking an average on the measured raw data. At this time, it is preferable to remove an abnormally high or low value from the measurement data by comparing with the reference value. The reference value may be taken as the final mean value of the snowfall measured during one previous turn (or more) (mean value obtained by subtracting the protrusion value and depression value). Therefore, the reference value is updated every time the rotation is measured.

A graph, measured illustratively for 24 points along a circle, is shown in FIG. In this example, the protrusion spikes 51, 52 and the dip 53 are removed.

Significant average data can be obtained by averaging the remaining values after significantly removing the abnormal values. When the data analysis is completed, the processing module 13 or the external server calculates the actual snowfall amount d ( t ) by applying sin θ ( t ) from t = 0 to t = n-1 generated in the calibration process, The average data, the calculated snowfall amount, and the circle measurement data.

If the measured data at a particular point (viewpoint or rotation angle) is steadily abnormally high or low, such an abnormality may have been caused by obstacles, obstructions by external substances or impurities on the glass cover. For example, in FIG. 6, the protruding value 61 shows a consistent abnormality while the depressed value 62 and protruding value 63 are transient. This may have been caused by moving leaves or scattered snowflakes. When this happens, the measurement system can report an event to an external server or generate an alarm signal.

The measurement system of the present invention should be calibrated through the following procedure before it is first installed in the field and measurement is performed. For calibration, a jig in the form of a box or a table as shown in Fig. 7 is used to provide a depth (height) Lref of a predetermined eye.

FIG. 8 is a diagram showing a calibration method of the present invention for a specific time t , and FIG. 9 is a flowchart showing an example of a calibration procedure. Let Lg ( t ) be the distance from the time t to the surface of the earth, and let Lr ( t ) be the distance to the surface of the jig. Lg ( t ) and Lr ( t ) are obtained by subtracting the distance (Lm) from the laser range finder to the mirror at the distance measured by the laser range finder.

The first step in the calibration process is to measure the distance from the laser range finder module 10 to the surface. t = after a reset to zero, that is put away (step S910), the surface after placing the mirror 11 in the initial position (S920), measuring a Lg (t) and the t, by rotation by φ the step motor 12 (Step S930). Is repeated until the step S930 to t = n (step S940) will be t = 0 measured Lg (t) at t = n-1, and to record.

Next, the jig 20 of Lref height is placed on the ground surface and initialized to t = 0 (step S950). Lr ( t ) is measured and t is increased by one by rotating the step motor 12 by phi (step S960). By repeating this, until the t = n (step S970) t = 0 measurement of Lr (t) at t = n-1, and to record.

Lref / (Lg (t) corresponding to Lg (t) and Lr for after measuring the (t) from t = 0 to t = n-1 sin θ (t) at each time t - Lr (t) (Step S980). The calculated sin θ ( t ) and the measured Lg ( t ) are used to calculate the snowfall d ( t ) using the measured Ls ( t ) to calculate the actual snow cover.

As described above, the point used for calibration is one point (Lref) higher than the ground and the ground. When the high point is closer to the laser measuring apparatus, the calibration process such as the degree of parallelism with the ground The measurement error is reduced, and it is convenient for implementation.

10 shows the protective cover 100 and the glass 101 surrounding the measuring device of the present invention. The entire assembly can be secured to a pole or structure to prevent the device from shaking or moving when the wind is blowing. The processing module 13 may be coupled to the communication module and configured to communicate with an external server for further processing of the data.

It is also possible to configure the laser range finder module 10 itself to be rotated at a slight angle instead of using the mirror 11.

The shape of the circle in the present invention is not critical, and may be a complete circle or an ellipse depending on the location of the apparatus and the angle at which the laser signal is projected. It is also possible to measure for any pattern projected onto the eye surface using a non-flat mirror.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them. In addition, although all of the components may be implemented as one independent hardware, some or all of the components may be selectively combined to perform a part or all of the functions in one or a plurality of hardware. As shown in FIG. The codes and code segments constituting the computer program may be easily deduced by those skilled in the art. Such a computer program can be stored in a computer-readable storage medium, readable and executed by a computer, thereby realizing an embodiment of the present invention.

It is to be understood that the terms "comprises", "comprising", or "having" as used in the foregoing description mean that a component can be implied unless specifically stated to the contrary, But should be construed as further including other elements.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

10 laser distance meter,
11 Mirror,
12 step motor,
13 processing module,
20 jig.

Claims (11)

Laser distance meter,
A target point changing means for changing a distance measurement target point of the laser range finder,
And a control unit for controlling the target point changing unit to measure the distance at a plurality of target points
And a snow cover. The apparatus according to claim 1, wherein the target point changing means
A step motor including a rotating shaft,
And a mirror for reflecting a laser beam from / to the laser distance measuring device, wherein the mirror is inclined at a predetermined angle with respect to a plane perpendicular to the rotation axis of the step motor,
/ RTI >
Wherein the control unit controls the step motor to control the laser distance measuring unit while rotating the mirror to measure the distance. 3. The method of claim 2,
The controller measures the distance by controlling the laser distance meter, repeats the process of rotating the step motor by a predetermined rotation angle ϕ and then measuring the distance until the mirror rotates one time, And calculates a snowfall amount from the snowfall amount. The method of claim 3,
Let L ( t ) be the measured distance from the mirror to the surface of the eye at an arbitrary measurement time t , Lg ( t ) be the distance from the mirror to the surface of the eye, and θ ( t ) be the angle between the laser beam and the surface , The snowfall amount d ( t ) at the measurement order t
d (t) = ((Lg (t) - Ls (t)) x sin θ (t)
Of the snowfall amount measuring device. 5. The method of claim 4,
The control unit calculates an average snowfall amount using only the remaining measured values by removing a value higher or lower than a predetermined rate,
Wherein the reference value is a final average value of a snowfall amount measured during at least one immediately preceding rotation. 6. The method according to any one of claims 1 to 5,
And communication means for transmitting the measured distance value to an external device. 6. The method according to any one of claims 1 to 5,
The snowfall measuring device is housed in a protective cover for protecting the apparatus,
Wherein the glass is provided in front of the mirror of the snowfall measuring device of the protective cover. A snowfall measuring method using a snowfall amount measuring apparatus for measuring a snowfall amount on a plurality of points scattered along a circle or an ellipse on an eye surface,
Sequentially measuring distances from the measuring device to a plurality of points on the circle or ellipse,
Calculating a snowfall amount from the plurality of measured distance values
Of the snowfall amount. 9. The method of claim 8,
Let Ls ( t ) be the measurement distance from the measurement device to the surface of the eye at any measurement point t , Lg ( t ) be the distance from the measurement device to the surface, and θ ( t ) be the angle at which the laser beam meets the surface. , The snowfall amount d ( t ) at the measurement point t is
d (t) = ((Lg (t) - Ls (t)) x sin θ (t)
Of the snowfall amount. 10. The method of claim 9, wherein calculating the snowfall comprises:
Further comprising the step of calculating a mean snowfall amount using only the remaining snowfall value by removing a snowfall amount value which is higher than or lower than a certain ratio from the average value of the snowfall amount at the plurality of measured points. 11. The method according to any one of claims 9 to 10, wherein before the snowfall measuring step
Sequentially measuring a distance Lg ( t ) to a plurality of points on the surface of the earth corresponding to the plurality of points on the circle or ellipse,
Sequentially measuring a distance Lr ( t ) to a plurality of points on the jig surface corresponding to the plurality of points on the circle or ellipse with a jig having a height Lref,
And calculating a sin θ ( t ) = Lref / ( Lg ( t ) - Lr ( t )) corresponding to the plurality of points.

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