Methods for thermo-optical analysis of snow and ice layers and thermo-optical analysis system

Abstract

Method for the thermo-optical analysis of snow and ice layers, in which a melt channel (11) is generated in snow and / or ice layers (7, 8, 9, 10) by means of a focused thermal energy source (5), which is a non-monochromatic energy source, by means of melting and / or sublimation processes, and in which the depth of the melt channel (11) is continuously measured in the direct area of ​​the melting or sublimation processes to determine the melting rate using an optical measuring device (6) which is collinear to the focused non-monochromatic energy source (5), wherein the measured values ​​of the optical measuring device (6) are forwarded to a computer-aided processing unit and stored, and subsequently material-specific characteristic values ​​of the snow and / or ice layers (7, 8, 9, 10) are calculated and information on the respective snow and / or ice layers (7, 8, 9, 10) is made available.

Description

[0001] The present invention relates to the field of measurement methods and environmental technology and concerns a method for the thermo-optical analysis of snow and ice layers as well as a thermo-optical analysis system. The thermo-optical analysis method and the thermo-optical analysis system according to the invention can be used, for example, for the stationary or mobile determination of the layer structure and composition of snow and ice layers in alpine regions.

[0002] In predominantly alpine areas, snow-laden slopes can be composed of different layers of snow or ice, which differ from each other in their structural composition, snow or ice depth and thickness, density, and the cohesion of the superimposed layers.

[0003] To determine the strength and thickness of snow or ice layers, it is well known that snowfall amounts and weather conditions are measured on reference areas near weather stations. Using the data obtained, the transformation processes occurring in the snow are simulated, allowing a layer profile to be simulated and calculated for each slope in the alpine region. To verify the accuracy of the simulation results, regular investigations of the snowpack are carried out at representative locations.

[0004] For conducting investigations on snow layers, manual as well as technical measurement methods using various technologies are known from the state of the art.

[0005] One example of a manual method is the sliding block test, in which a block measuring 2 × 1.5 × 3 m is used. 3The edge length is dug out of the snow. The slope must be at least 30°. After a hand profile test, varying loads are applied to the block in an attempt to provoke a sliding of the layers. This test has the highest predictive accuracy and is regularly carried out by avalanche warning services.

[0006] Also known are ramming technologies and the ramming profile test, in which the snow profile is indirectly determined by measuring snow strength using a ram probe. This test measures the snow's resistance to driving a ram rod for specific depth ranges. The tip of the ram probe has a diameter of 4 cm, which severely limits the depth resolution. The use of a so-called SnowMicroPen in the ramming profile test has a significantly slimmer tip and is driven into the snow at a constant speed, recording the tip pressure and the frictional resistance of the shaft. This results in a considerably better depth resolution. A drilling depth of 1.25 m can be achieved within 2 minutes. However, the drilling depth is limited by the length of the rod.

[0007] German patent DE 195 03 017 A1 describes a device for measuring the layer structure of a snowpack, a so-called snow profile measuring probe. The probe has a rod-shaped carrier body that can be inserted into a snow layer. A position detection device determines the penetration depth of the carrier body in the snowpack. A measuring device is provided at one end of the carrier body for measuring the snow profile.

[0008] German patent DE 10 2009 039 716 B3 discloses a non-destructive measurement method for determining snowpack structure, in particular for detecting weak layers for avalanche forecasting without the presence of personnel. This method measures weak layers as discontinuities of physical parameters using an upward-facing ground-penetrating radar from below the snowpack. It uses exclusively electromagnetic signals at an angle of incidence perpendicular to the surface. In this active measurement method, each measurement point at each layer boundary is additionally measured with an acoustic signal. Furthermore, each measurement point is also measured at different angles of incidence of the transmitted signals to capture the angular dependence of the relevant physical parameters of the snowpack. For this purpose, the transmitter and receiver, which can be arranged individually or in combination, are separated by at least a first separation.The coupling of electromagnetic and acoustic data with the physical parameters relevant to snow stratification, in particular density, is carried out via a mathematical inversion procedure.

[0009] From DE 10 2016 104 270 A1, a device and a method for determining a layered structure of a snow cover are known, comprising the steps of providing at least one optical excitation signal, which is emitted at an insertion point adjustable in the depth direction of the snow cover, of detecting at least one optical measurement quantity that indicates a portion of the optical excitation signal remitted by the snow cover within a predetermined measurement environment of the insertion point, and of providing the at least one detected optical measurement quantity for determining at least one optical parameter indicating the structure of the snow cover.

[0010] From DE 103 01 789 A1 a method for determining parameters of snow or ice is known, in which the parameters are determined by comparing the melting energy to be applied to melt a certain volume of snow or ice, wherein the melting energy is applied with a laser, as well as a device suitable for carrying out the method.

[0011] And from DE 40 25 577 A1, a device for non-contact measurement of the distance from an object is known, comprising an optical device that focuses a measuring beam consisting of a light beam, in particular a laser beam, onto the measuring point of the object. The device also includes a detector for determining the focal point deviation from the surface of the object, which receives light reflected from the measuring point, and in particular a measuring lens that focuses the reflected light through an aperture onto a light-sensitive sensor, as well as an evaluation unit that receives sensor signals.

[0012] A disadvantage of existing solutions is that the analysis of snow and ice layers is carried out by people at measurement sites located outside the alpine danger zone. However, in the direct avalanche danger zone, analysis by people is not possible due to the high risk. Another disadvantage is that known analysis systems are only applicable to thin layers and the simulated results are inaccurate. Finally, known methods for analyzing snow and ice layers are time-consuming and expensive.

[0013] The object of the present invention is to provide a method for analyzing snow and ice layers and an analysis system with which the analysis of snow and ice layers through multiple layers of snow or ice can be carried out in a simple and cost-effective manner with high accuracy of the analysis results. An object of the present invention is also to reduce the risk to persons during the measurement of snow and ice layers.

[0014] The problem is solved with the features contained in the patent claims, whereby the invention also includes combinations of the individual dependent patent claims in the sense of an AND connection, as long as they do not mutually exclude each other.

[0015] The problem according to the invention is solved by a method for the thermo-optical analysis of snow and ice layers, in which a melt channel is created in snow and / or ice layers by means of a focused thermal energy source, which is a non-monochromatic energy source, through melting and / or sublimation processes, and in which the depth of the melt channel is continuously measured in the direct area of ​​the melting or sublimation processes to determine the melting rate using an optical measuring device that is collinear to the focused non-monochromatic energy source, wherein the measured values ​​of the optical measuring device are forwarded to a computer-aided computing unit and stored, and subsequently material-specific characteristic values ​​of the snow and / or ice layers are calculated and information on the respective snow and / or ice layers is made available.

[0016] Advantageously, a CW laser and / or a pulsed laser is used as the focused thermal energy source.

[0017] Advantageously, the channel is also created by sublimating the snow or ice using a pulsed laser, with a laser having a power of 0.1W to 300W and a wavelength of 100nm to 50µm being particularly advantageous as a focused thermal energy source.

[0018] Furthermore, it is advantageous to use an LED-based or infrared-based energy source as a focused non-monochromatic energy source.

[0019] In a further advantageous embodiment of the method, the optical measurement of the depth of the melt channel is realized via a TOF method and / or by means of emitted intensity waves, wherein the optical measurement of the depth of the melt channel is particularly advantageous with a wavelength of 100nm to 5cm.

[0020] It is advantageous if the focused thermal energy input occurs at an angle of 10° to 90° to the snow or ice surface.

[0021] Furthermore, it is advantageous that the melting velocity and the channel depth are transmitted as measured values ​​to a computer-aided computing unit.

[0022] In a further advantageous embodiment of the method, the respective layer density, layer height and / or layer type are provided as information on the snow and ice layers.

[0023] It is also advantageous to use correlation tables to determine information about the snow and ice layers.

[0024] It is also advantageous that the information on the respective snow and / or ice layers is transmitted to an output unit via a wireless radio connection.

[0025] The problem according to the invention is also solved by a thermo-optical analysis system comprising a thermal energy source in the form of a focused non-monochromatic energy source for generating a focused thermal energy input into a snow and / or ice layer, an optical measuring device for generating an optical measurement signal for measuring local parameters, wherein the optical measurement signal is collinear with the thermal propagation direction of the thermal energy source, and a computer-aided computing unit at least for acquiring measured values ​​from the optical measuring device.

[0026] It is advantageous if the collinear alignment of the thermal energy source and the optical measuring device is achieved by dichroic mirrors, optical gratings, optical prisms, radiation splitters and / or polarization filters.

[0027] It is also advantageous if the direction of the focused thermal energy input of the thermal energy source is variably adjustable, and it is particularly advantageous if the directions of the focused thermal energy input of the thermal energy source and of the optical measurement signal of the optical measuring device are adjustable at an angle of 10° to 90° to the snow or ice surface.

[0028] In a further advantageous embodiment, the computer-aided computing unit can additionally calculate the material-specific characteristic values ​​and / or transmit the information on the respective snow and / or ice layers to an output unit, wherein at least one wireless radio device is particularly advantageous for transmitting the information to the output unit.

[0029] Equally advantageous is the thermo-optical analysis system, which is designed as a manual, stationary or mobile analysis system.

[0030] And equally advantageously, the thermo-optical analysis system is a component of a drone, an aircraft, or a vehicle.

[0031] The solution according to the invention provides, for the first time, a method and an analysis system for investigating snow and ice layers, enabling the simple and cost-effective analysis of snow and ice layers, for example, in direct avalanche danger zones, without the need for personnel, even in areas with large layer thicknesses. This new method and analysis system makes it possible, for the first time, to make highly accurate avalanche danger predictions in alpine regions without endangering people. Furthermore, the thermo-optical analysis method and system according to the invention offer flexible, localized application options for determining snow or ice profiles.

[0032] This is achieved through a process that uses a focused thermal energy source to create a channel in snow and / or ice layers by melting or sublimating the snow or ice. During the melting or sublimation processes, an optical measuring device continuously measures the depth of the resulting channel and thus the melting rate. Depending on the properties of the snow or ice and the radiation intensity of the focused thermal energy source, different melting or sublimation rates can be achieved.

[0033] The melting or sublimation rates each represent a specific composition and snow density of the snow or ice layer and allow, for example, concrete statements about the density and size of the snow or ice layer, from which the danger of avalanches can be derived.

[0034] To measure the melt channel depth, an optical measuring device is inserted into the beam path of the thermal energy source, whereby the thermal beam of the focused thermal energy source and the optical beam of the optical measuring device are collinearly aligned. This collinear alignment of the focused thermal and optical beams can be achieved, for example, by beam splitters, dichroic filters, or polarizing filters, which enable very precise alignment and superposition of the two beam types.

[0035] Within the scope of the invention, a focused thermal energy source is understood to be a device with which directed thermal energy radiation is generated, which selectively realizes melting or sublimation processes in the ice or snow in a defined local area, thereby creating a melt channel in the snow or ice layers.

[0036] For an accurate determination of the melting progress, it is crucial that the optical measurement of the melt channel depth is performed at the deepest point of the melt channel, in the area where the melting or sublimation processes are directly occurring. By simultaneously melting or sublimating the snow or ice and continuously measuring the melt channel depth, a high-resolution profile of the snow or ice layers is generated as a displacement-time function. Changes in the melting or sublimation rate, represented by the rate of progression of the melt channel depth, mark the beginning and end of a snow or ice layer with a specific density.

[0037] In a particularly advantageous embodiment of the method and analysis system, a laser with a continuously generated laser beam (continuous wave laser or CW laser) or a pulsed laser is used as the focused thermal energy source for generating the melt channel. The use of a pulsed laser offers the advantage, especially when generating a melt channel in ice, that due to the brief, high thermal energy input, the snow or ice does not melt but is sublimated directly from the solid to the gaseous state. This prevents the accumulation of meltwater at the lowest point of the melt channel when the channel is generated essentially perpendicularly, leading to a more accurate measurement of the melt channel depth and thus to a more precise analysis of the snow or ice strata.This avoids the correction of inaccurate measurements of the melt channel depth by accumulated meltwater at the lowest point of the melt channel.

[0038] When measuring snow layers, meltwater seeps into the snow during the installation of the melt channel. This does not significantly affect the depth measurement. The seepage of meltwater into the snow alters its properties, and this altered property is measured shortly thereafter. This is disadvantageous and is avoided according to the invention by ensuring that the gravity-driven propagation direction of the meltwater differs from the propagation direction of the melt channel and thus of the laser. In an advantageous embodiment of the invention, the focused thermal energy input into the snow or ice layers occurs at an angle of 10° to 90° to the snow or ice surface.The focused thermal energy input at an angle of 10° to 90° to the snow or ice surface prevents the accumulation of meltwater at the lowest point of the melt channel due to the gravitational force of the melted snow or ice, thus enabling a more accurate measurement of the melt channel depth. However, it is crucial that both the focused thermal energy source and the optical measuring unit are collinearly aligned, which means that the optical measurement of the melt channel depth must also be performed at an angle of 10° to 90° to the snow or ice surface.

[0039] According to the invention, the melt channel depth determined by the optical measuring device is transmitted as measured values ​​to a computer-aided computing unit and stored as a function of the temporal progress of the depth of the melt channel.

[0040] For the continuous measurement of the depth of the melt channel, in an advantageous embodiment the optical Time of Flight (TOF) method or an optical method using intensity waves can be used, in which pulses are emitted and their return time is measured.

[0041] The optical measurement of the depth of the melt channel is carried out with a wavelength of 100nm to 5cm, wherein the selection of the wavelength of the optical measurement is advantageously chosen such that the wavelength of the optical measurement is smaller than the diameter of the melt channel. Selecting a shorter wavelength compared to the diameter of the melting channel has the technical effect that the wave used to measure the depth of the melting channel penetrates the melting channel and is not reflected at the entrance of the melting channel.

[0042] In an advantageous embodiment of the invention, the computer-aided processing unit can be a component of the analysis system, in which the material-specific properties of the snow or ice layers are subsequently calculated and information on the respective snow and ice layers is provided. Alternatively, the measured values ​​can be acquired by the optical measuring device and transmitted directly via a wireless radio connection to a computer-aided processing unit located remotely from the analysis system, where the material-specific properties of the snow or ice layers are calculated and information on the respective snow and ice layers is provided.

[0043] The thermo-optical analysis system according to the invention can advantageously be designed as a manual analysis system in the form of a handheld device, a stationary analysis system, or particularly advantageously as a mobile analysis system. In particular, it is possible that the mobile analysis system is a component of a drone (UAV - Unmanned Aerial Vehicle) or another radio-controlled driverless vehicle or aircraft.

[0044] The mobile design of the thermo-optical analysis system eliminates the need for any infrastructure for stationary mounting. A further significant advantage of a mobile analysis system is that operators can remain outside the avalanche-prone area and still perform measurements on snow or ice layers within that area.

[0045] The thermo-optical analysis system according to the invention also offers the advantage of being small, compact, and lightweight. This results in a particularly cost-effective analysis system that is easy to manufacture and can be used flexibly in various alpine regions.

[0046] The invention will now be explained in more detail using an exemplary embodiment. Fig. 1 - a schematic representation of a thermo-optical analysis system, Fig. 2 - a schematic representation of a drone-based thermo-optical analysis system, Fig. 3 - a schematic diagram of a thermo-optical analysis system, Fig. 4 - an exemplary melt depth-time profile of a melt channel through 4 different snow layers, Fig. 5 - a melt rate-depth profile of a melt channel through 4 different snow layers, Fig. 6 - a snow density profile plotted over the depth of the snow layer and calculated as a material-specific characteristic value, and Fig. 7 - the snow thicknesses, which were provided from a snow depth-time diagram as information about the respective snow layer.

[0047] The Fig. Figure 1 shows the schematic structure of a thermo-optical analysis system according to the invention. Fig. Figure 2 shows a mobile analysis system that is part of a drone, with the drone performing the analysis of the snow layers on a snow-covered slope with a total of 4 different snow layers.

[0048] After Fig. In a housing that protects the analysis system from environmental influences and is part of the thermo-optical analysis system, a thermal laser is arranged as a CW laser. This laser generates a continuous laser beam with a constant power of 10 W, which is deflected by a mirror and directed into the snow layers 1–4 at an angle of 30° to the perpendicular. The CW laser melts a melt channel into the snow layers. A second optical laser continuously measures the depth of the melt channel using laser distance measurement. The laser beam of the second optical laser is deflected by a dichroic mirror and thus propagates collinearly with the laser beam of the CW laser. Measurements from the second optical laser are acquired and recorded to create a displacement-time diagram of the melt depth.

[0049] During the melting of all four layers, a melting depth-time profile is recorded according to Fig. 3 recorded. From this, the melting rates are determined according to Fig. 4 calculated and the material-specific properties of the snow density at the different snow depths according to Fig. 5 as well as the thickness of the individual snow layers according to Fig. 6 derived.

[0050] Information regarding the snow layers is now provided stating that snow layer 1 has a thickness of 20 cm and a density of 50 kg / m³. 3 This indicates that the first layer of snow is fresh snow. The second layer of snow has a thickness of 10 cm and a density of 200 kg / m³. 3 This is heavily wind-packed snow. Snow layer 3 has a thickness of 20 cm and a density of 150 kg / m³. 3This is why it is a dangerous layer of unstable snow. It is unstable and can cause the overlying snow layers 1 and 2 to slide. Snow layer 4 has a thickness of 5 cm and a density of 300 kg / m³. 3 and consists of dry, settled old snow.

[0051] The snow profiles of the snow layers determined, taking into account previous findings and correlation tables, allow for reliable predictions about the avalanche danger in the relevant alpine area. Reference sign 1 mirror 2 Focused thermal beam 3 Dichromatic mirror 4 Optical beam of the distance measuring system 5. Focused thermal energy source 6 Optical laser distance measuring system 7 Snow layer 1 8 Snow layer 2 9 Snow layer 3 10 Snow layer 4 11 Melt channel 12 cases 13 Drone 14 Drone-based thermo-optical analysis system 15 Collinearly aligned beams of the optical distance measuring system and the aligned focused thermal radiator

Claims

[1] Method for the thermo-optical analysis of snow and ice layers, in which a melting channel (11) is created in snow and / or ice layers (7, 8, 9, 10) by melting and / or sublimation processes by means of a focused thermal energy source (5), which is a non-monochromatic energy source, and in the process, using an optical measuring device (6) which is aligned collinearly to the focused non-monochromatic energy source (5), the depth of the melting channel (11) is continuously measured in the direct area of the melting or sublimation processes taking place in order to determine the melting rate, wherein the measured values of the optical measuring device (6) are forwarded to a computer-assisted processing unit and stored, and subsequently material-specific characteristic values of the snow and / or ice layers (7, 8, 9, 10) are calculated and information on the respective snow and / or ice layers (7, 8, 9, 10) is made available. [2] Method according to claim 1, wherein a CW laser and / or a pulsed laser is used as the focused thermal energy source (5). [3] Method according to claim 2, wherein the channel (11) is produced by sublimation of the snow or ice (7, 8, 9, 10) using a pulsed laser. [4] Method according to at least one of the preceding claims, in which a laser with a power of 0.1W to 300W and a wavelength of 100nm to 50µm is used as the focused thermal energy source (5). [5] Method according to claim 4, wherein an LED-based or infrared-based energy source is used as the focused non-monochromatic energy source (5). [6] Method according to at least one of the preceding claims, in which the optical measurement of the depth of the melt channel (11) is realized by means of a TOF method and / or by means of emitted intensity waves. [7] Method according to claim 6, wherein the optical measurement of the depth of the melt channel (11) is carried out with a wavelength of 100nm to 5cm. [8] Method according to at least one of the preceding claims, in which the focused thermal energy input (5) takes place at an angle of 10° to 90° to the snow or ice surface. [9] Method according to at least one of the preceding claims, in which the melting rate and the channel depth are transmitted as measured values to a computer-assisted computing unit. [10] Method according to at least one of the preceding claims, in which the respective layer density, the layer height and / or the layer type are provided as information on the snow and ice layers (7, 8, 9, 10). [11] Method according to at least one of the preceding claims, in which correlation tables are used to determine the information on the snow and ice layers (7, 8, 9, 10). [12] Method according to at least one of the preceding claims, in which the information on the respective snow and / or ice layers (7, 8, 9, 10) is transmitted to an output unit by means of a wireless radio connection. [13] Thermo-optical analysis system, comprising a focused non-monochromatic energy source (5) for generating a focused thermal energy input (2) into a snow and / or ice layer (7, 8, 9, 10), an optical measuring device (6) for generating an optical measuring signal for measuring local parameters, wherein the optical measuring signal is aligned collinearly (15) to the thermal propagation direction of the thermal energy source, and a computer-assisted computing unit at least for recording measured values of the optical measuring device (6). [14] Thermo-optical analysis system according to claim 13, wherein the collinear alignment of the thermal energy source (5) and the optical measuring device (6) is realized by dichromatic mirrors (3), optical gratings, an optical prism, beam splitters and / or polarization filters. [15] Thermo-optical analysis system according to claim 13, wherein the direction of the focused thermal energy input of the thermal energy source (5) is variably adjustable. [16] Thermo-optical analysis system according to claim 15, wherein the directions of the focused thermal energy input of the thermal energy source (5) and the optical measuring signal of the optical measuring device (6) are adjustable at an angle of 10° to 90° to the snow or ice surface. [17] Thermo-optical analysis system according to claim 13, in which the computer-assisted computing unit can additionally calculate material-specific characteristic values and / or transmit information on the respective snow and / or ice layers to an output unit. [18] Thermo-optical analysis system according to claim 17, wherein at least one wireless radio device is provided for transmitting the information to the output unit. [19] Thermo-optical analysis system according to claim 13, which is designed as a manual, stationary or mobile analysis system (13, 14). [20] Thermo-optical analysis system according to at least one of the preceding claims 13 to 19, which is a component of a drone (13), a flying object or a vehicle.

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