JP2011002420A - Snowfall detector and method of detecting snowfall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in a conventional snowfall detector that an accurate state of snowfall has not been detected since data on suspended matter other than snow such as fallen leaves have also been captured as snowfall data to calculate snowfall intensity, etc.SOLUTION: A pulse laser is projected to suspended matter in a scan domain. In cases where reflected pulse light from the suspended matter is continuously detected, an angle range with the suspended matter positioned therein is found from the number of continuous reflected pulses. The distance to the suspended matter is measured from the length of time between the projecting of the pulse laser and the receiving thereof. The size of the suspended matter is calculated from the angle range (proportioned to the number of continuous detections) and the distance. In cases where the size of the suspended matter is equal to or larger than a prescribed value, the suspended matter is determined to be foreign matter other than snow to exclude the data on the suspended matter from snowfall data.

Description

  The present invention relates to a snowfall detection device and a snowfall detection method used for weather observation and the like.

  As a conventional snowfall detection device, the measurement light is projected from the light projecting unit to the measurement area, the reflected light from the snowflake on which the measurement light hits is received by the light receiving unit, and the count of detection pulses generated by the light reception is counted. A technique for calculating the snowfall intensity by performing is disclosed (for example, see Patent Document 1).

  Also, as a conventional distance measuring device, the reflected pulse light from the object irradiated with the pulsed light is received, and the distance to the object is measured by measuring the round trip time of the pulsed light from the generation of the pulse to the reception of the reflected pulsed light A technique is disclosed (for example, see Patent Document 2).

JP-A-61-175550 JP-A-6-289135

  The conventional snowfall detection device calculates snowfall intensity assuming that all the reflected light received by the light receiving part is reflected from the snowflake, so it excludes foreign matters other than snowflakes, such as fallen leaves, etc. There was a problem that it was not possible to output a strong snowfall intensity. In addition, since the size of the snowflake could not be measured with the conventional apparatus, it was impossible to detect with high accuracy that the snowfall intensity was calculated in consideration of the size of the snowflake.

  The present invention has been made to solve the above-described problems. When the size of the suspended matter in the measurement region is obtained, if the size is detected to be greater than a predetermined value (threshold), It is assumed that the suspended matter is a foreign object other than snowflakes, and it is excluded from the snowfall data to obtain a snowfall detection device that can calculate snowfall intensity with high accuracy, and snowfall that can detect the size of the suspended matter The purpose is to obtain a detection method.

  The snowfall detecting device according to the present invention includes a light projecting unit that projects laser light, a scanning unit that scans the laser light within a predetermined angle of a plane including the light projecting unit, and a floating object in the scanning region of the laser light. A light receiving unit that detects the reflected light of the reflected laser beam, and calculates the angle at which the reflected light is detected and the distance between the light projecting unit and the suspended matter from the data of the reflected light. A signal processing unit is provided that calculates the size of the suspended matter based on the distance data and outputs the snowfall intensity reflecting the size of the suspended matter.

  Further, the snowfall detection method according to the present invention includes a step of scanning the laser optical axis of the pulse laser and continuously projecting the pulse laser to the scanning area within a predetermined angle, and is reflected by the suspended matter in the scanning area. A step of detecting a reflected pulse of the pulse laser, a step of detecting the number of reflected pulses in which the reflected pulse is continuous, and a step of calculating an average measurement distance from the light projecting unit to the suspended matter from the data of the reflected pulse. The step of calculating the size of the suspended matter based on the number of reflected pulses and the average measured distance is included.

  According to the snowfall detection device of the present invention, since the size of the suspended matter can be obtained, the snowfall intensity can be calculated by reflecting the size of the suspended matter, and the detected suspended matter size data is obtained. It can be used to determine whether or not the floating object has a size corresponding to snow.

  Further, according to the snowfall detection method of the present invention, the size of the suspended matter can be detected with high accuracy from the number of continuous reflected pulses from one suspended matter and the average measurement distance to the suspended matter.

It is a block diagram of the snowfall detection apparatus by Embodiment 1 of this invention. It is explanatory drawing for demonstrating the calculation procedure of the magnitude | size of a snowflake by the snowfall detection apparatus of Embodiment 1 of this invention. It is a flowchart which shows the snowfall detection flow of Embodiment 1 of this invention. It is a layout view showing an installation example of the snowfall detection device of Embodiment 1 of the present invention. It is a block diagram of the snowfall detection apparatus by Embodiment 2 of this invention. It is a relationship figure showing the relationship between the magnitude | size of the snowflake of Embodiment 2 of this invention, the reflected light intensity from a snowflake, and the ease of melting of snow. It is a block diagram of the snowfall detection apparatus by Embodiment 3 of this invention. It is explanatory drawing for demonstrating the measurement range example for snowfall intensity | strength calculation of Embodiment 3 of this invention, and snow cover height calculation. It is a block diagram of the snowfall detection apparatus by which the temperature conditions by Embodiment 4 of this invention were considered.

Embodiment 1 FIG.
Next, Embodiment 1 of the present invention will be described with reference to FIGS.
As shown in the configuration diagram of FIG. 1, the snowfall detection device 10 according to the first embodiment of the present invention is mainly configured by a light projecting / receiving unit integrated sensor 11 and a signal processing unit 12. The light projecting / receiving unit integrated sensor 11 scans the laser light 14 on a light projecting unit that projects a laser beam (pulse laser) 14 and a measurement region 15 (or scanning region) within a predetermined angle of a plane including the light projecting unit. And a light receiving unit that receives the reflected light (reflected pulse) of the laser beam reflected by the suspended matter 13 (snow or the like) in the scanning region of the laser beam 14, a light projecting unit, a scanning unit, The light receiving unit is integrated (hereinafter referred to as a sensor). The signal processing unit 12 calculates the detection position of the suspended matter 13 (distance and direction from the sensor 11) from the reflected pulse data, and the size of the suspended matter 13 based on the angle (direction) and distance data. This is a calculation processing unit for the reflected pulse information that calculates the snowfall intensity signal 1a reflecting the size of the suspended matter 13 and outputs it to the outside. In the first embodiment, the laser beam 14 is scanned in a horizontal plane.

In the snowfall detection device 10 of the first embodiment, the sensor 11 can detect the number of pulse lasers successively irradiated on one suspended matter 13 as the number of continuous reflected pulses.
As shown in FIG. 2, when a snowflake 13a is detected in the measurement region 15, the idea of calculating the size of the snowflake 13a (a size that can be regarded as a diameter when the snowflake is considered as a sphere) is calculated from the number of reflected pulses. Show. In FIG. 2, the measurement range angle width (scanning angle width) is θ, the number of division points measured by the sensor 11 within the measurement range is N (for example, N = 300 when θ = 30 °), and the sensor 11 to the snowflake. The average value of measurement distances up to 13a (average measurement distance) is L, the number of pulse lasers continuously irradiated to one snowflake 13a, that is, the number of reflected pulses detected continuously by the sensor 11 is K (the number of continuous detections). The diameter R of the snowflake 13a can be expressed as shown in the following equation.
R ≒ L × (θ / N × K)
Here, θ represents the arc length of the angle θ per unit radius.

In the example of FIG. 2, since the four pulse lasers (laser beams 14a to 14d) are continuously irradiated on the snowflake 13a, the number of continuous reflected pulses (the number of continuous detections) K = 4. If the cross section of the snowflake 13a is circular, the diameter R of the snowflake 13a is considered to be the size of an arc chord having an angular width θ _K in which the reflected pulse is measured and having a measurement distance L as a radius. However, when the measurement distance L is assumed to be about 1.5 meters at the maximum, and the floating object to be measured is considered to be about several centimeters (less than 5 centimeters) such as snow, the dimensional difference between the string and the arc is In most cases, it can be kept small and R can be approximated to the length of the arc. It goes without saying that the signal processing unit 12 can also correct R more precisely to the size of the string instead of the arc.

Furthermore, there are various methods for measuring the distance with the laser beam 14 to obtain the measurement distance L. For example, the distance can be calculated from the time taken from light projection to light reception using pulsed light.
Further, the detection direction indicating where the snowflake 13a is located in the measurement region 15 can be specified by synchronizing the scanning period and the timing of laser projection.

Next, the operation will be described. FIG. 3 is a flowchart of the snowfall intensity calculation process. Here, for example, the snowfall intensity calculation is performed so as to measure only a certain unit time (for example, 5 minutes) and to calculate one snowfall intensity value as a result.
When the snowfall detection device is operated and the snowfall intensity calculation process is started, snowfall measurement is performed as shown in step S11 while the snowfall intensity calculation cycle time has elapsed (loop 1). Here, the laser beam 14 is scanned from the light projecting / receiving unit-integrated sensor 11 toward the measurement region 15 at a constant period, whereby the detection position (distance and direction from the sensor 11) of the snowflake in the measurement region 15 is obtained. The data obtained by light reception by the sensor 11 is sent to the signal processing unit 12 (one-scan snowfall measurement). The data sent to the signal processing unit 12 may include reflected light intensity in addition to the distance and direction from the sensor 11. A method of determining the ease of snow accumulation at the same time when calculating the snowfall intensity using the reflected light intensity data will be described in the second embodiment.

When snowfall measurement starts, a loop (loop 2) for calculating the size of snow for one scan starts, and the process proceeds to step S12. In steps S12 to S19, the size of the snowflake 13a is calculated from the detection position of the snowflake 13a. Here, in FIG. 2, it is necessary to count the number of points (continuous detection number) K detected continuously for a certain snowflake 13 a, and the method is as follows.
First, the laser beam axis of the laser beam 14 (pulse laser) is scanned, and the laser beam 14 is continuously projected in order from the end of the measurement range angular width θ (the position where the angle is 0 ° or θ) to obtain a snowflake 13a. Is detected (when there is no current snowflake detection at step S12 and no previous snowflake detection at step S17). Subsequently, when the reflected light (reflected pulse) reflected by the suspended matter in the measurement range is detected and the place where the snowflake 13a is detected is detected (in the case of step S12), the process continues in step S15. The detection number K is incremented by 1, and the distance values detected in step S16 are integrated. Thereafter, by repeating steps S15 and S16 until the snowflake 13a is no longer detected, K for the snowflake 13a and the average measured distance of the snowflake 13a to be detected are obtained. When the reflected pulse is no longer detected (when no snowflake is detected at this time in step S12, and when the previous snowflake detection is detected at step S17), the detected position of the snowflake 13a and the number of consecutive detections K are detected at step S18. The size is calculated, and the continuous detection number K and the measured distance integrated value are reset in step S19.

  Here, even if the reflected pulse is detected continuously, there is a possibility that two snowflakes at different distances may be detected continuously. Therefore, in the case where the previous snowflake detection is made in step S13, in step S14, The difference from the current measured distance value is taken, and if there is a difference greater than a certain value, it is considered that separate snowflakes have been detected, and the counting of the continuous detection number is interrupted. The constant value here can be set to about 1.5 to 2 times, for example, with reference to the distance measurement accuracy of the sensor 11.

Next, calculation of the size of the snowflake 13a in step S18 will be described. In FIG. 2, when the number of division points measured by the sensor 11 with respect to the measurement range angular width θ [rad] is N and the detection distance of the snowflake is L, the calculated value R of the size of the snowflake 13 a is R = It can be obtained by applying the equation of L × (θ / N × K).
Subsequently, in step S21, the size of the snowflake 13a thus obtained is integrated for every fixed value, and used as pre-data for calculating the snowfall intensity. Note that the next loop 2 after steps S16 and S21 represents a repeated portion of calculation and integration of the size of the snowflake. Also, since the snowfall intensity calculation is not performed in units of one scan, but is calculated every certain time (snowfall intensity calculation cycle time: specifically 5 minutes, etc.), loop 1 is the snowfall intensity calculation cycle time. This means that the scanning is repeated while elapses.

Finally, the snowfall intensity is calculated in step S22. Here, when the integrated value of the size R of the snowflake 13a accumulated in step S21 with respect to the snowfall intensity calculation cycle is expressed as ΣR, the snowfall intensity S is expressed by the following equation using the adjustment coefficients A, B, and C. expressed.
S = A × ΣR + B × ΣR ² + C × ΣR ³
The above formula is based on the idea that the snowfall intensity is proportional to the length element R of the snowflake, the area element R ^{2 of} the snowflake, and the volume element R ^{3 of the} snowflake.
In addition, in step S20 before accumulation in step S21, in the case where the size of the accumulated snowflake is a value that is too large as a normal snowflake (for example, 5 cm), that is, the size value of the snowflake is larger than the exclusion threshold (predetermined value). If it is larger, it is considered that foreign matter other than snowflakes such as fallen leaves is being measured, and is excluded from the accumulation target. On the other hand, when the size value of the snowflake is smaller than the exclusion threshold, the influence of false detection can be suppressed by making it an accumulation target.

  As described above, by using the snowfall detection device of the present invention, the laser optical axis of the pulse laser is scanned, and the pulse laser is continuously projected onto the scanning region within a predetermined angle (step S11), and is within the scanning region. The reflected pulse of the pulse laser reflected by the floating object is detected (step S12), the number of reflected pulses in which the reflected pulse continues is detected (step S15), and the floating object is detected from the light projecting unit (sensor) from the reflected pulse data. Since the average measurement distance is calculated (step S16) and the size of the suspended matter is calculated based on the number of reflected pulses and the average measured distance (step S18), the size of the suspended matter can be obtained. If it is detected that the suspended matter is larger than the threshold value, it can be excluded from the snowfall data by judging that the suspended matter is a foreign object other than snow, reflecting the size of the snow particles It is possible to calculate a highly accurate snowfall intensity in.

FIG. 4 is a layout diagram illustrating an installation example of the snow detection device according to the first embodiment of the present invention. FIG. 4 (a) shows the snow detection device 10 installed on the roof of the building 102 facing the road 101. FIG. 4B shows an example of detecting a snowfall state on the road 101 (in the sky). FIG. 4B shows a snowfall state on the rail 103 of the railroad when the snowfall detection device 10 installed on the steel tower 104 provided along the railroad line. An example of detection is shown. The installation height of the snowfall detection device 10 is set to a height that does not fill the snowfall. Thus, if the snowfall state of roads and railways can be accurately detected by the snowfall detection device of the present invention, traffic safety can be secured, and snowfall information detected for weather observation and automatic control of the snowmelt device can be utilized. It becomes possible.
In addition to roads and railway lines, the snow detection device of the present invention can be used as meteorological data by accurately detecting snow conditions by removing foreign matter data such as fallen leaves. Needless to say.

Embodiment 2. FIG.
FIG. 5 is a block diagram of a snowfall detection device 20 according to Embodiment 2 of the present invention.
The snowfall intensity is calculated according to the same procedure as in the first embodiment, and the ease of snow accumulation is calculated from the size of the snowflake obtained in the snowfall intensity calculation process and the laser reflected light intensity detected by the sensor 21 (light receiving unit). The signal processing unit 22 can output a snow accumulation ease signal 1b indicating the degree.
As shown in FIG. 6, the ease of snow accumulation is relatively easy to melt in dendritic snow with large snowflakes and high reflected light intensity, and conversely with spherical snow with small snowflakes and low reflected light intensity. Therefore, it is possible to measure the ease of snow accumulation based on the size (large and small) of snowflakes and the intensity of reflected light (strong and weak).
Even when the snowfall intensity is the same, the amount of snowfall varies depending on the ease of snow accumulation, and in the second embodiment, the snowfall state can be detected in more detail.

Embodiment 3 FIG.
FIG. 7 is a block diagram of a snowfall detection device 30 according to Embodiment 3 of the present invention.
Although the laser beam scanning direction in the first embodiment is a horizontal direction, in the third embodiment, the laser beam 34 projected from the light projecting / receiving unit integrated sensor 31 is the ground surface 36 (the horizontal plane). Are scanned in the vertical direction in a plane perpendicular to the vertical axis. And it is characterized by having comprised so that the snow cover height h can be measured from the data which scanned the area | region including the ground 36 where the projection direction of a laser is below horizontal. The height of the snow cover 37 is output from the signal processing unit 32 to the outside as the snow cover height signal 3c. In addition, using the same apparatus, the floating matter 33 in the measurement region 35 was detected and obtained using the data obtained by projecting the laser beam 34 in a direction above the horizontal plane, as in the first embodiment. It is possible to calculate the snowfall intensity from the data by the signal processing unit 32 and output the snowfall intensity signal 3a. In that case, the data of only the region where the snow cover 37 is not included in the measurement range in the laser beam scanning range (the measurement region 35, the range from the scanning angle 0 ° (downward in the vertical direction) to φ _MAX ) is used. When the scanning angle from the vertical direction phi ₀ and alpha, may be in the range of 90 ° <α <φ _MAX.

Next, a procedure for calculating the snow cover height h will be described with reference to FIG.
Calculation of snow height h, when the scan angle φ1 becomes the maximum value that can be measured on the ground 36, the laser in the direction of the ground 36 in the laser beam scanning range enters the measurement range _{β (φ 0 <β <φ} 1) By projecting the light 43a and measuring the distance L from the sensor 31 to the snow cover 37, it can be obtained by the following equation. Here, H is the height of the sensor 31. In FIG. 8, reference numeral 34 a indicates a laser beam for calculating snow cover height projected in the direction β.
h = H-cos (β)
Actually, when the distance L to the snow cover 37 is measured, there is a possibility of detecting a suspended matter. Therefore, measurement is performed several times and an intermediate value is set as a measurement value. In this way, the snow cover height h is measured and output from the signal processing unit 32 to the outside as the snow cover height signal 3c.
As described above, since the snowfall intensity and the snow cover height can be measured with one snowfall detection device, the installation space and the cost can be reduced as compared with the case where the snowfall intensity is individually prepared.

Embodiment 4 FIG.
In the snowfall intensity calculation flow shown in FIG. 3 of the first embodiment, when a floating substance having a size greater than or equal to a predetermined value is detected, it is determined that the floating substance is a foreign object other than snow and is excluded from the snowfall data. In the fourth embodiment, a snowfall temperature condition for observing snow is set. If the temperature does not fall within the temperature range, the suspended matter 13 is confirmed in the measurement region 15. Even if it is a case, processing shall be performed so that it is not recognized as snowfall data. In FIG. 9, the block diagram of the snowfall detection apparatus 40 of this Embodiment 4 is shown. As shown in FIG. 9, the snowfall detection device 40 of the present invention includes a thermometer 42, and the temperature in the measurement region 15 can be measured by the thermometer 42.
Further, since the snow temperature condition 44 is added to the signal processing unit 43, the air temperature data obtained from the thermometer 42 is collated with the snow temperature condition 44, and on a warm day when no snow is observed, floating other than snow. It is possible to adjust so that an object is not detected as snow.

  As described above, by adding the snow temperature condition 44, the snow intensity signal 4a output from the signal processor 43 can be obtained as a more accurate value. In addition, it has been shown that the thermometer 42 is provided in the signal processing unit 43 as a method for taking in the air temperature data from the outside, and the output value is obtained. Whether the thermometer 42 is integrated with the sensor 41 or separated. Needless to say, since the installation conditions differ depending on the type of the thermometer and the like, it is desirable that the arrangement be suitable for measurement.

DESCRIPTION OF SYMBOLS 1a, 3a, 4a Snowfall intensity signal 1b Easiness of snow accumulation 3c Snowfall height signal 10, 20, 30, 40 Snowfall detection device 11, 21, 31, 41 Light emitting / receiving unit integrated sensor 12, 22, 32, 43 Signal processor 13, 33 Floating matter 13a Snow flakes 14, 14a-14d, 34, 34a Laser light (pulse laser)
15, 35 Measurement area 36 Ground 37 Snow cover 42 Thermometer 44 Snow temperature conditions.

Claims (8)

  A light projecting unit that projects laser light, a scanning unit that scans the laser light within a predetermined angle of a plane including the light projecting unit, and a reflected light of the laser light reflected by a floating object in the scanning region of the laser light The light receiving unit for detecting the reflected light, the angle at which the reflected light is detected and the distance between the light projecting unit and the floating object are calculated from the data of the reflected light, and the floating object is calculated based on the data on the angle and the distance. And a signal processing unit that outputs a snowfall intensity reflecting the size of the suspended matter.   The signal processing unit determines that the suspended matter is a foreign matter other than snow when the size of the suspended matter exceeds a predetermined value, and excludes the suspended matter from the data for calculating the snowfall intensity. The snowfall detection device according to claim 1.   The said signal processing part determines the degree of the ease of snow accumulation from the magnitude | size data of the said suspended | floating matter, and the intensity data of the said reflected light which can be measured in the said light-receiving part. The snowfall detection device described.   The snowfall detection device according to claim 1, wherein the laser beam is projected in a horizontal plane.   The laser beam is projected in a plane perpendicular to the ground, and the signal processing unit obtains data for calculating the snowfall intensity from a region where the projection direction is above horizontal. The snowfall detection device according to claim 1.   The laser beam is projected in a plane perpendicular to the ground, and the signal processing unit calculates a snow cover height on the ground from a region where the projection direction is lower than horizontal and includes the ground. The snow detection device according to claim 1, wherein data is obtained.   The signal processing unit captures the temperature data of the scanning region from the outside, compares the temperature data with a temperature condition at which snowfall can be observed, and if the temperature data deviates from the temperature condition, the floating object is removed. The snowfall detection device according to claim 1, wherein the snowfall detection device is determined to be a foreign object other than snow and is excluded from the data for calculating the snowfall intensity.   Scanning the laser optical axis of the pulse laser and projecting the pulse laser continuously to the scanning area within a predetermined angle; detecting the reflected pulse of the pulse laser reflected by the suspended matter in the scanning area A step of detecting the number of reflected pulses in which the reflected pulses are continuous; a step of calculating an average measurement distance from the light projecting unit to the suspended matter from the data of the reflected pulses; and a step of calculating the number of reflected pulses and the average measured distance. A snowfall detection method characterized by including a step of calculating the size of the suspended matter.

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