A near-infrared optical method for distinguishing dry and wet snow on a compacted snow surface.

Abstract

This invention provides a near-infrared optical method for distinguishing between dry and wet snow on a compacted snow surface. The method includes the following steps: First, determine whether the snow on the ground is compacted or loose. The surface height of the snow is obtained using laser ranging, and the equivalent thickness of the snow is obtained based on the differences in snow absorption at different near-infrared bands. The snow is determined to be compacted or loose by comparing its surface thickness with its equivalent thickness. Then, the difference in absorption and reflection of water and ice at the 1400nm and 1550nm wavelengths in the near-infrared band is used to determine whether the compacted snow surface contains dry or wet snow. This method subdivides complex road surface contaminants and uses a composite approach to determine the type of snow and its surface, providing a quantitative method for identifying snow contaminants. It has significant application value for assessing road surface conditions, especially airport runway surface conditions.

Description

Technical Field

[0001] This invention belongs to the field of optical sensing and measurement of road pollutants, and in particular relates to a near-infrared optical method for distinguishing between dry snow and wet snow on a compacted snow surface. Background Technology

[0002] The presence of contaminants on airport runway surfaces has a significant impact on aircraft, especially commercial aircraft, during takeoff and landing. Therefore, accurately identifying runway surface contaminants is crucial for airport controllers to determine whether aircraft can take off and land normally. In northern my country, winters are dominated by snow, but when car or aircraft tires drive over snow, it compacts the snow. If this compacted snow is not cleared, it can easily become even wetter and slippery when covered again. Determining whether the compacted snow is dry or wet is essential for assessing the suitability of an airport runway for takeoff and landing. This also presents a significant challenge for aircraft crews and airport controllers operating from contaminated runways. A significant decrease in the runway's coefficient of friction can lead to insufficient tire traction, severely impacting aircraft safety during takeoff and landing.

[0003] To address this, the Civil Aviation Administration of my country issued the "Rules for Assessing and Reporting the Surface Condition of Transport Airport Runways" in 2021. These rules explicitly stipulate that a clear report must be issued regarding whether compacted snow surfaces contain dry or wet snow. This is crucial for accurately assessing airport runway surface conditions. However, currently, there are no effective measuring devices or even relevant standards for determining whether compacted snow surfaces are dry or wet. Many airports rely solely on visual inspection to determine the dryness or wetness of compacted snow surfaces. This lacks clear standards and is highly subjective. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a near-infrared optical method for distinguishing between dry and wet snow on a compacted snow surface.

[0005] The aforementioned optical method for distinguishing between dry and wet snow on a compacted snow surface of an airport runway includes the following steps: First, based on ground temperature and two infrared signals of different wavelengths, the method distinguishes between snow and water accumulation on the ground, and determines the equivalent light absorption thickness of the snow based on the difference between the two infrared signals. Then, based on the relationship between the equivalent light absorption thickness and the snow surface thickness, the method determines whether the snow is compacted or loose. Finally, based on the difference in near-infrared light signal reflection, the method determines whether the compacted snow surface is dry or wet.

[0006] The method for distinguishing between dry and wet snow on a compacted road surface using near-infrared optics is characterized by the following: the prerequisite for determining snow accumulation on the road surface is that the road surface temperature is below zero degrees Celsius, and the absorption difference between the two near-infrared bands is significant. Then, based on the intensity difference of the two detected infrared light signals, the equivalent thickness of the snow accumulation on the ground is obtained using the Lambert-Beer law of light absorption and a calibration method.

[0007] The near-infrared optical method for distinguishing dry and wet snow on a compacted road surface is characterized by measuring the snow surface thickness using a laser ranging principle. By fixing the position of the laser ranging probe, the distance from the upper surface of the snow to the probe position is measured to obtain the snow surface thickness.

[0008] The method for distinguishing between dry and wet snow on a compacted snow surface using near-infrared optics is characterized by measuring and comparing the equivalent light absorption thickness of the snow with the surface thickness. When the surface thickness is lower than the equivalent thickness, the snow is compacted. When the surface thickness is higher than the equivalent thickness, the snow is loose. This allows for the determination of whether the ground surface has compacted or loose snow.

[0009] The method for distinguishing between dry and wet snow on a compacted snow surface using near-infrared optics is characterized by determining whether the compacted snow surface contains dry or wet snow through the absorption difference between two near-infrared wavelengths at 1400nm and 1550nm. The conditions for a compacted snow surface to contain dry snow are: high reflection intensity at 1400nm, low reflection intensity at 1550nm, and a surface temperature below zero degrees Celsius. The conditions for a compacted snow surface to contain wet snow are: low reflection intensity at 1400nm, high reflection intensity at 1550nm, and a surface temperature above zero degrees Celsius.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] This invention employs a multispectral composite method to measure and distinguish between dry and wet snow on compacted snow surfaces. Current road condition monitoring equipment can only indicate whether the road surface is wet or snowy, but cannot further differentiate between compacted snow and surface contaminants. This invention determines snow compaction by measuring and comparing the difference between the surface thickness and the equivalent thickness of light absorption. When the surface thickness is lower than the equivalent thickness, the snow is compacted. When the surface thickness is higher than the equivalent thickness, the snow is loose. Current monitoring equipment cannot effectively measure the difference between loose and compacted snow, and there is no fixed standard for judging whether snow is compacted. Furthermore, surface contaminants on compacted snow cannot be effectively identified. The method of this invention provides a clear standard for judging whether snow is compacted. It also provides clear near-infrared spectral judgment rules for surface contaminants on snow. Based on the near-infrared optical method for distinguishing between dry and wet snow on compacted snow surfaces provided by this invention, the developed monitoring equipment will provide important theoretical basis for real-time monitoring of road surfaces, especially airport runway surfaces. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0013] Figure 1 A flowchart of a near-infrared optical method for distinguishing dry and wet snow on a compacted snow surface provided by the present invention. Detailed Implementation

[0014] The following describes in detail, with reference to the accompanying drawings and specific embodiments, a near-infrared optical method for distinguishing dry snow and wet snow on a compacted snow surface provided by the present invention.

[0015] like Figure 1 The diagram illustrates a near-infrared optical method for distinguishing between dry and wet snow on a compacted snow surface. First, the equivalent thickness of the snow's light absorption is measured. Before measuring the equivalent thickness, the ground temperature and two infrared signals of different wavelengths are used to distinguish between snow and water accumulation. Then, the equivalent thickness of the snow's light absorption is determined based on the difference between the two infrared signals. Next, the surface thickness of the snow is obtained using laser ranging. Then, the equivalent thickness of the light absorption is compared with the surface thickness of the snow to determine whether the snow is compacted or loose. Finally, the difference in near-infrared light signal reflection is used to determine whether the compacted snow surface is dry or wet.

[0016] The specific measurement principle in this invention is explained below.

[0017] The principle for measuring the equivalent thickness of snow light absorption is as follows: First, the ground temperature is measured, and the equivalent thickness of snow light absorption is determined and measured when it is below zero degrees Celsius. The equivalent thickness of snow light absorption is equivalent to the thickness of ice under the same absorption conditions. Two wavelengths in the near-infrared band, 980nm and 1310nm, are selected as the light source for measuring the equivalent thickness of snow light absorption. Using a pre-calibration method, the difference between the light return signals of the two wavelengths, 980nm and 1310nm, is determined under different ice thicknesses. A calibration curve is plotted with the difference between the light return signals of the two wavelengths, 980nm and 1310nm, as the horizontal axis and the ice thickness as the vertical axis. When the difference between the light return signals of the two wavelengths, 980nm and 1310nm, is obtained again from the road surface, this difference is substituted into the curve to determine the corresponding thickness value on the vertical axis, and this value is taken as the equivalent thickness of snow light absorption.

[0018] The principle for measuring snow surface thickness is as follows: The thickness of the snow surface is measured using the standard laser rangefinder principle. The snow surface thickness is obtained by subtracting the height of the laser rangefinder from the height of the probe above the ground from the height of the laser rangefinder above the snow surface.

[0019] Compare the equivalent thickness of snow cover in terms of light absorption with the surface thickness of the snow cover. If the surface thickness of the snow cover is lower than the equivalent thickness of snow cover in terms of light absorption, it is classified as compacted snow. If the surface thickness of the snow cover is higher than the equivalent thickness of snow cover in terms of light absorption, it is classified as loose snow.

[0020] Determining whether compacted snow is dry or wet. The difference between wet and dry snow is that wet snow has a higher water content than dry snow. The presence of dry or wet snow on a compacted snow surface is determined by the difference in absorption of water and ice at the 1400nm and 1550nm wavelengths in the near-infrared band. For a compacted snow surface to be dry, the following conditions must be met: high reflection intensity at 1400nm and low reflection intensity at 1550nm, and the surface temperature must be below zero degrees Celsius. For a compacted snow surface to be wet, the following conditions must be met: low reflection intensity at 1400nm and high reflection intensity at 1550nm, and the surface temperature must be above zero degrees Celsius.

Claims

1. A method for near-infrared optical discrimination of dry and wet snow on a compacted snow surface, the process comprising: First, based on the ground temperature and two infrared signals of different wavelengths, the surface is distinguished as snow or water. Then, based on the difference in reflection signals between the 980nm and 1310nm infrared beams, and combined with the calibration curve, the equivalent thickness of the snow's light absorption is determined. Next, based on the relationship between the equivalent thickness of light absorption and the snow surface thickness, it is determined whether the snow is compacted or loose. Finally, based on the difference in reflection between the two near-infrared beams at 1400nm and 1550nm, the compacted snow surface is judged to be dry or wet. The conditions for a dry compacted snow surface are: high reflection intensity at 1400nm, low reflection intensity at 1550nm, and a surface temperature below zero degrees Celsius. The conditions for a wet compacted snow surface are: low reflection intensity at 1400nm, high reflection intensity at 1550nm, and a surface temperature above zero degrees Celsius.

2. A method of near-infrared optical discrimination of dry and wet snow on a pavement compacted snow surface according to claim 1, characterized in that: The premise for judging the snow on the road surface is that the road surface temperature is below zero degrees Celsius and the absorption difference between the two near-infrared bands is significant. Then, based on the difference in intensity of the two detected infrared light signals, the equivalent thickness of the snow on the road surface is obtained by applying the Lambert-Beer law of light absorption and using a calibration method.

3. The near-infrared optical method for distinguishing dry snow and wet snow on a compacted snow surface according to claim 1, characterized in that: The method for measuring the surface thickness of snow is based on the principle of laser ranging. By fixing the position of the laser ranging probe, the distance from the upper surface of the snow to the probe position is measured to obtain the surface thickness of the snow.

4. The near-infrared optical method for distinguishing dry snow and wet snow on a compacted snow surface according to claim 1, characterized in that: By measuring and comparing the equivalent thickness of light absorption of snow with the thickness of the snow surface, it can be determined whether the ground is compacted or loose snow when the surface thickness is lower than the equivalent thickness and the surface thickness is higher than the equivalent thickness.

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