Oil film bidirectional reflection characteristic field measurement device and oil film thickness inversion correction method

Abstract

The invention discloses an oil film bidirectional reflection characteristic on-site measurement device and an oil film thickness inversion correction method, and belongs to the technical field of image processing, and the oil film bidirectional reflection characteristic on-site measurement device comprises an experiment pool which contains an oil-water mixed sample; the annular guide rail is arranged around the experimental water tank; the camera support is arranged on the annular guide rail in a sliding mode, and a fixing base capable of rotating around a horizontal shaft and a vertical shaft is arranged at the upper end of the camera support; the hyperspectral camera is fixed on the fixed seat and is used for measuring the radiance of the experimental pool; and the irradiance meter is used for measuring the irradiance of the sunlight. The oil film bidirectional reflection characteristic on-site measurement device is simpler in structure and easy to implement, and the spectrum difference caused by different visual angles of the sensor is eliminated. And the accuracy and reliability of oil type identification and thickness inversion are greatly improved.

Description

Field measurement device for bidirectional reflection characteristics of oil film and method for inversion correction of oil film thickness Technical Field

[0001] This invention belongs to the field of liquid level measurement technology, specifically, it relates to an on-site measurement device for the bidirectional reflection characteristics of oil film and a method for inverting and correcting oil film thickness. Background Technology

[0002] Marine oil spills are a significant threat to marine ecosystems and coastal economies. Statistics show that between 2014 and 2019, 94% of global oil spills originated from human activities, including shipping, offshore drilling accidents, and illegal discharges. As a major importer and consumer of crude oil, my country experiences continuous growth in its maritime oil transportation, leading to a corresponding increase in oil spill risks. The type and thickness of the oil slick formed by a marine spill directly determine emergency recovery and remediation strategies. Therefore, rapid identification of oil types and quantitative inversion of oil slick thickness are crucial for improving oil spill response efficiency.

[0003] Optical remote sensing offers advantages such as multi-band and high resolution in oil spill identification. Currently, methods such as threshold segmentation and spectral reflectance models are commonly used to detect oil slick area and thickness. The optical properties of marine oil slicks exhibit significant angle dependence, displaying different brightness characteristics at different angles. Current threshold-based oil slick area detection and thickness inversion algorithms are based on algorithms established at a specific measurement angle, without considering detection errors caused by different observation angles. Figure 1 shows an RGB image of the Gulf of Mexico deepwater horizon oil spill event on May 1, 2010, taken by a MISR (Multi-angle Imaging SpectroRadiometer). At this time, the solar zenith angle was 20°, and the relative azimuth angle captured by the AF camera on the MISR was 129°, with an observed zenith angle of 26°. Figure 2 shows the variation of oil film spectral data with angle. As can be seen from Figure 2, the bidirectional reflectance of the oil film causes significant differences in the observed radiation intensity at different observation angles. This leads to large errors in current mainstream oil film area detection algorithms, such as the threshold method, when applied to different observation angles. Most existing optical remote sensing methods do not fully consider the influence of observation geometry and solar geometry on spectral reflectance characteristics, neglecting the bidirectional reflectance of the oil film.

[0004] The bidirectional reflectance distribution function (BRDF) is a key parameter characterizing the bidirectional reflectance properties of ground objects. Currently, BRDF measurement primarily relies on two methods: Monte Carlo simulation and laboratory experiments. For example, some studies calculate BRDF using Monte Carlo simulation, while others utilize hyperspectral measurement platforms and xenon lamps to simulate sunlight to measure BRDF data for oil films of varying thicknesses. As shown in Figure 3, existing BRDF measurement devices, in order to obtain infinitesimally small solid angles and differential radiance, require sensors to observe objects in various spatial directions and process the reflectance values ​​from each observation direction to characterize the object's directional reflectance characteristics. This necessitates minimizing the divergence angle of the light source and the field of view of the sensor; high positioning accuracy of the light source and sensor; and a sufficient number of incident and observation directions, thus leading to a complex structure.

[0005] However, these methods are limited to indoor or simulated ideal environments, failing to achieve on-site measurements under real sea conditions and lacking systematic multi-angle hyperspectral datasets covering different environmental conditions. Consequently, the reliability and applicability of their results are very limited. Currently, BRDF measurement devices are cumbersome and cannot effectively reflect the bidirectional reflectance characteristics of ground objects under natural light (sunlight). Summary of the Invention

[0006] To address the technical problem that existing marine oil spill thickness inversion methods do not consider the influence of solar and observation geometry on the reflection spectrum and neglect the bidirectional reflection characteristics of the oil film, thus affecting the stability of identification, this invention proposes an on-site measurement device for the bidirectional reflection characteristics of the oil film and an oil film thickness inversion correction method, which can solve the above problems.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an on-site measurement device for the bidirectional reflectance characteristics of an oil film, comprising: an experimental water tank containing an oil-water mixture sample; an annular guide rail arranged around the experimental water tank; a camera bracket slidably mounted on the annular guide rail, the upper end of the camera bracket having a fixed base capable of rotating around a horizontal and a vertical axis; and a hyperspectral camera fixed on the fixed base, with its lens facing the experimental water tank. The hyperspectral camera has a spectral range covering the visible to near-infrared band and is used to measure the radiance of the experimental water tank. A radiometer is used to measure the irradiance of sunlight. .

[0008] In some embodiments, the measurement method of the on-site measurement device for the bidirectional reflection characteristics of the oil film includes: a radiance acquisition step, in which the camera bracket is controlled to slide at least one revolution along the annular guide rail to adjust the observation azimuth angle of the hyperspectral camera, and the hyperspectral camera acquires radiance at a set frequency. Simultaneously acquire the observation azimuth angle of the hyperspectral camera. And observing the zenith angle Rotate the fixed base about the horizontal axis and adjust the observation zenith angle of the hyperspectral camera according to the set step size. Repeat the radiance acquisition steps until all preset observation zenith angles for radiance acquisition are completed; calculate the corresponding solar zenith angle based on the radiance acquisition time and geographical latitude and longitude. and solar azimuth ; Calculate in angle Bidirectional reflectance factor below: Where λ is the wavelength of the collected light. For parameters The radiance collected below, For parameters The irradiance collected below; calculate each With corrected bidirectional reflectance factor The conversion coefficients between them are used to obtain the correction factor. Construct an angle-correction factor lookup table, wherein the angle includes ;in, To observe the zenith angle bidirectional reflectance at time .

[0009] In some embodiments, the internal partitions of the experimental water tank form several independent smaller tanks, each containing an oil-water mixture sample with a different oil film thickness. Where i represents the number of the pool and is a positive integer, the thickness of the oil film in the pool increases with the increase of i; the measurement method of the field measurement device for the bidirectional reflection characteristics of the oil film also includes the step of determining the reflection threshold. In the actual inversion correction, when the correction bidirectional reflection factor is not greater than the reflection threshold, the thickness of the oil film is inverted using the first thickness inversion model; otherwise, the thickness of the oil film is inverted using the second thickness inversion model. The first thickness inversion model is a model based on Beer-Lambert's law, and the second thickness inversion model is a two-beam interference model.

[0010] In some embodiments, the step of determining the reflection threshold includes: calculating the thickness of the oil film in each small pool using a first thickness inversion model, and obtaining... And by using the second thickness inversion model to calculate the thickness of the oil film in each small pool, the following results were obtained. ;according to calculate The inversion accuracy, fitting out The inversion accuracy curve is the accuracy curve of the first thickness inversion model, and based on... calculate The inversion accuracy, fitting out The inversion accuracy curve is the accuracy curve of the second thickness inversion model; the thickness value corresponding to the intersection of the accuracy curves of the first and second thickness inversion models is calculated as the thickness threshold; the corrected bidirectional reflectance factor corresponding to the thickness threshold in the first thickness inversion model is calculated as the first reflectance threshold. The corrected bidirectional reflectance factor corresponding to the thickness threshold in the second thickness inversion model is calculated, which is the second reflectance threshold. Compare the first reflection threshold Second reflection threshold The larger value is used as the reflection threshold. .

[0011] In some embodiments, the first thickness inversion model is: ,in Let 'a' be the reflectance of the background water, 'a' be the absorption coefficient, and 'd' be the oil film thickness to be inverted; the second thickness inversion model is... , where A0-A4 are the model parameters respectively.

[0012] In some embodiments, the oil film thickness in each small pool ranges from 0 μm to 500 μm.

[0013] In some embodiments, the radiance acquisition step further includes covering the lens of the hyperspectral imager with a black cloth to acquire dark current data before each data acquisition by the hyperspectral camera, and optimizing the acquisition parameters through the instrument's built-in automatic exposure and focus functions.

[0014] An oil film thickness inversion correction method based on the bidirectional reflectance characteristics of oil film, which is based on the field measurement device for the bidirectional reflectance characteristics of oil film described above, the oil film thickness correction method includes: (11) acquiring spectral data of the target area through remote sensing or telemetry, and calculating the bidirectional reflectance factor of the spectral data. (12) Find the correction factor corresponding to the spectral data through the lookup table. , will the Correction is performed to obtain the corrected bidirectional reflectance factor. (13) When If the thickness of the oil film is not greater than the reflection threshold, the first thickness inversion model is used to invert the thickness of the oil film; otherwise, the second thickness inversion model is used to invert the thickness of the oil film.

[0015] In some embodiments, the method further includes a step of calculating the amount of oil spill based on the calculated oil spill thickness and oil spill area.

[0016] In some embodiments, the method for calculating the oil spill volume is as follows: Where s is the area corresponding to one pixel. This represents the thickness of the oil spill at sea corresponding to the i-th pixel, and n is the total number of oil spill pixels.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are as follows: The field measurement device for the bidirectional reflectance characteristics of oil film of the present invention, compared with the existing measurement device for bidirectional reflectance distribution function (BRDF), adopts a different oil film bidirectional reflectance characteristic model description method. This model only needs to obtain the observation zenith angle and observation azimuth angle from multiple angles, and combine the solar zenith angle and solar azimuth angle from multiple directions to collect the radiance and irradiance at different angle combinations. This measurement device can change the observation azimuth angle of the hyperspectral camera by setting a ring guide rail and the camera bracket driving the hyperspectral camera to move along the ring guide rail. The hyperspectral camera is fixed on a fixed base that can rotate around a horizontal axis by a fixed base to change the observation zenith angle. Combined with the natural changes in the solar zenith angle and solar azimuth angle of sunlight, several different angles can be obtained through the above combinations, so as to realize the data acquisition and construction of the bidirectional reflectance factor model of the present invention. The structure of this solution is simpler and easier to implement.

[0018] The oil film thickness inversion correction method of the present invention acquires spectral data of the target area through remote sensing or telemetry, and calculates the bidirectional reflectance factor of the spectral data. Simultaneously, based on the angle-correction factor lookup table obtained from the field measurement device for the bidirectional reflectance characteristics of the oil film, the correction factor corresponding to the spectral data can be found. This is used to correct the bidirectional reflectance factor, normalizing any observation angle to the same direction and eliminating spectral differences caused by different sensor viewing angles. This significantly improves the accuracy and reliability of oil type identification and thickness inversion. The spectral characteristics of different oil types are more easily distinguished after angle normalization, avoiding misjudgments caused by different observation angles. It solves the problem of interference to the oil film spectrum caused by the observation angle. The lookup table and correction method constructed from the field experiment are applied to satellite and UAV remote sensing data to achieve automatic oil type identification, accurate oil film thickness inversion, and reliable oil spill estimation, thereby effectively transforming field measurement results into practical monitoring capabilities with higher processing efficiency.

[0019] Other features and advantages of the present invention will become clearer after reading the detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. Attached Figure Description

[0020] Figure 1 is an RGB image of the Gulf of Mexico deepwater horizon oil spill event on May 1, 2010, captured by MISR; Figure 2 is a graph showing the relationship between each band of the original MISR data and different observation angles; Figure 3 is a schematic diagram of the structure of an existing bidirectional reflectance distribution function measurement device; Figure 4 is a schematic diagram of the structure of an embodiment of the field measurement device for bidirectional reflectance characteristics of oil film proposed in this invention; Figure 5 is a schematic diagram of the fixing structure of the hyperspectral camera and camera bracket in an embodiment of the field measurement device for bidirectional reflectance characteristics of oil film proposed in this invention; Figure 6 is a graph showing the relationship between the inversion accuracy and thickness of two different thickness inversion models in an embodiment of the field measurement device for bidirectional reflectance characteristics of oil film proposed in this invention; Figure 7 is a graph showing the relationship between each band of the corrected MISR data and different observation angles in an embodiment of the oil film thickness inversion correction method based on bidirectional reflectance characteristics of oil film proposed in this invention. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: This example proposes an on-site measurement device for the bidirectional reflection characteristics of an oil film, as shown in Figure 4, which includes: an experimental water tank 11, a ring rail 12, a camera bracket 13, a hyperspectral camera 14, and an irradiance meter 15.

[0024] The experimental pool 11 contained a mixed oil-water sample. The oil-water ratio was precisely controlled, and the oil film thickness was known.

[0025] The experimental water tank 11 is set up with 12 ring guide rails.

[0026] The camera bracket 13 is slidably mounted on the annular guide rail 12. The upper end of the camera bracket 13 is provided with a fixed base 16 that can rotate around a horizontal axis. The hyperspectral camera 14 is fixed on the fixed base 16, and the imaging lens of the hyperspectral camera 14 is set towards the experimental water pool. The spectral range of the hyperspectral camera 14 covers the visible light to near-infrared band and is used to measure the radiance of the oil film in the experimental water pool 11.

[0027] The irradiance meter 15 is used to measure the irradiance of sunlight. Solar irradiance is the solar radiation energy (power) incident vertically on a unit area per unit time, and it is a core indicator for measuring the instantaneous intensity of solar energy.

[0028] Compared with existing bidirectional reflectance distribution function (BRDF) measurement devices, the field measurement device for bidirectional reflectance characteristics of oil film in this embodiment adopts a different oil film bidirectional reflectance characteristic model description method. This model only needs to acquire the observation zenith angle and observation azimuth angle from multiple angles, and combine the solar zenith angle and solar azimuth angle from multiple directions to collect the radiance and irradiance at different angle combinations. This measurement device sets up a ring guide rail, and the camera bracket drives the hyperspectral camera to move along the ring guide rail, which can change the observation azimuth angle of the hyperspectral camera. The hyperspectral camera is fixed on a fixed base that can rotate around a horizontal axis through a fixed base to change the observation zenith angle. Combined with the natural changes in the solar zenith angle and solar azimuth angle of sunlight, several different angles can be obtained through the above combinations, so as to realize the data acquisition and construction of the bidirectional reflectance factor model of the present invention. The structure of this solution is simpler and easier to implement.

[0029] In some embodiments, the measurement method of the on-site measurement device for bidirectional reflection characteristics of oil film includes: a radiance acquisition step, in which the camera bracket 13 is controlled to slide at least one revolution along the annular guide rail 12 to adjust the observation azimuth angle of the hyperspectral camera 14, and the hyperspectral camera 14 acquires radiance at a set frequency. Simultaneously acquire the observation azimuth angle of the hyperspectral camera. And observing the zenith angle If the observation azimuth angle of the hyperspectral camera 14 is adjusted, its relative azimuth angle with the sun will also change.

[0030] The camera mount 13 moves the hyperspectral camera 14 along the annular guide rail 12, thereby adjusting the observation azimuth angle of the hyperspectral camera 14. .

[0031] The bottom of the camera bracket 13 can be equipped with pulleys that match the circular guide rail 12, and together with the drive motor, the camera bracket 13 can be driven to move automatically.

[0032] The position of the camera bracket 13 on the annular guide rail 12 can also be manually moved, which can achieve the purpose of adjusting the camera bracket 13 to drive the hyperspectral camera 14 to move along the annular guide rail 12 in this solution.

[0033] Rotate the mounting base 16 around the horizontal axis and adjust the observation zenith angle of the hyperspectral camera according to the set step size. Then, repeat the radiance acquisition step until all preset radiance acquisitions at the observation zenith angle are completed.

[0034] As shown in Figure 5, the hyperspectral camera 14 is fixed on the mounting base 16. The mounting base 16 is rotatably connected to the connecting arm 18 via the first rotating shaft 17. The first rotating shaft 17 is a horizontal axis and is fixed at one end of the connecting arm 18. The mounting base 16 can rotate around the first rotating shaft 17. The rotation of the mounting base 16 can be manually controlled, or it can be automatically driven to rotate by a motor. The automatic rotation method is a conventional technical means and will not be described in detail here.

[0035] In some embodiments, the other end of the connecting arm 18 is rotatably connected to the camera bracket 13 via a second rotating shaft 19. The second rotating shaft 19 is fixed to the camera bracket 13 and is a vertical axis. The connecting arm 18 can rotate around the second rotating shaft 19 to drive the hyperspectral camera 14 to rotate around the vertical axis via the fixed base 16, thereby adjusting the observation azimuth angle of the hyperspectral camera 14 at small angles. The camera bracket 13 moves the hyperspectral camera 14 along the annular guide rail 12 to adjust the observation azimuth angle of the hyperspectral camera 14 at large angles. These two adjustment methods avoid the problem of blind spots in observation. It is understood that the connecting arm 18 can rotate around the second rotating shaft 19 manually or by a motor.

[0036] In some embodiments, the corresponding solar zenith angle is calculated based on the time of radiance acquisition and the geographical latitude and longitude. and solar azimuth The hyperspectral camera 14 has a built-in function that can simultaneously obtain the time of radiance acquisition and geographical latitude and longitude, and then use this information to calculate the solar zenith angle. and solar azimuth The calculation method can be implemented using existing technology, and will not be elaborated here.

[0037] Calculation in angle Bidirectional reflectance factor below: .

[0038] Where λ is the wavelength of the collected light. For parameters The radiance collected below, For parameters The irradiance collected below.

[0039] Calculate each With corrected bidirectional reflectance factor The conversion coefficients between them are used to obtain the correction factor. Construct an angle-correction factor lookup table, where the angle includes... .

[0040] in, To observe the zenith angle bidirectional reflectance at time Observing the zenith angle This is also known as the nadir direction.

[0041] The constructed lookup table possesses high physical completeness and representativeness. It is no longer a single-angle spectral library, but a database reflecting the variation of oil film optical properties in a multi-dimensional parameter space. Based on the lookup table, a precise multi-angle data correction algorithm based on physical interpolation can be developed. This solves the pain points of existing technologies, such as data fragmentation, missing parameters, and inability to correct angular effects, transforming data processing from simple filtering or averaging to precise normalization based on a physical model.

[0042] A multidimensional lookup table is established based on data obtained from the bidirectional reflection characteristic measuring device. This lookup table includes multiple variables such as instrument zenith angle, relative azimuth angle, solar zenith angle, and BRF. Each set of variable data contains multiple field-measured data. Based on the bidirectional reflection characteristics of the oil film, a normalized correction model is established from any observation angle to the nadir direction, i.e., the instrument zenith angle 0° (i.e., the nadir angle), using multi-angle BRF data obtained from field measurements. The core mathematical expression for the correction is: .

[0043] The BRF value is in the nadir direction. These are the original BRF values. It is a correction factor.

[0044] By unifying remote sensing data from various angles to a standard observation geometry nadir orientation, spectral differences caused by varying sensor viewing angles are eliminated. This significantly improves the accuracy and reliability of oil type identification and thickness inversion. The spectral characteristics of different oil types are more easily distinguished after angle normalization, avoiding misjudgments due to different observation angles. The relationship between thickness and BRF is inherently affected by angle; the corrected data makes the spectral-based thickness inversion model more accurate and stable.

[0045] In some embodiments, the internal partitions of the experimental pool form several independent smaller pools, each containing an oil-water mixture sample with a different oil film thickness. , where i represents the number of the pool, which is a positive integer, and the thickness of the oil film in the pool increases as i increases.

[0046] The measurement method of the field measurement device for bidirectional reflection characteristics of oil film also includes the step of determining the reflection threshold. In the actual inversion correction, when the correction bidirectional reflection factor is not greater than the reflection threshold, the thickness of the oil film is inverted using the first thickness inversion model; otherwise, the thickness of the oil film is inverted using the second thickness inversion model. The first thickness inversion model is a model based on Beer-Lambert's law, and the second thickness inversion model is a two-beam interference model.

[0047] As shown in Figure 6, experimental data has verified that, based on the fundamental principle of the Lambert-Beer law, the absorption characteristics of the oil film can be estimated by measuring its transmittance, and then the thickness can be inverted. This method is particularly suitable for inverting thick oil films.

[0048] The two-beam interference model utilizes the functional relationship between oil film thickness and reflectivity for inversion, which is also a thickness inversion method. This method is particularly suitable for the inversion of thin oil films.

[0049] Based on optical principles, bidirectional reflectance factor The accuracy is negatively correlated with oil film thickness; that is, the thicker the oil film, the smaller the BRF. Therefore, this scheme first calculates the oil film thickness corresponding to the same or similar inversion accuracy for the two inversion models. It leverages the advantage of different models for inverting different thicknesses. When the thickness exceeds this threshold, inversion is performed based on the fundamental principle of the Lambert-Beer law. Otherwise, a two-beam interferometry model is used for inversion.

[0050] In actual inversion, the thickness is unknown, making it impossible to determine which model to use. Therefore, this scheme calculates the bidirectional reflectance factor corresponding to the thickness threshold in each model. The reflection threshold is determined based on the bidirectional reflectance factor. Since the BRF decreases with increasing thickness, if the corrected bidirectional reflectance factor is not greater than the reflection threshold, it indicates a larger thickness, and the first thickness inversion model is used to invert the oil film thickness. Otherwise, the second thickness inversion model is used. Therefore, the selection of the thickness inversion model is simplified to a judgment based on the corrected bidirectional reflectance factor, and this scheme has higher inversion efficiency.

[0051] In some embodiments, the step of determining the reflection threshold includes: calculating the thickness of the oil film in each small pool using a first thickness inversion model, and obtaining... And by using the second thickness inversion model to calculate the thickness of the oil film in each small pool, the following results were obtained. .

[0052] according to calculate The inversion accuracy, fitting out The inversion accuracy curve is the accuracy curve of the first thickness inversion model, and based on... calculate The inversion accuracy, fitting out The inversion accuracy curve is the accuracy curve of the second thickness inversion model, as shown in Figure 6.

[0053] The thickness value corresponding to the intersection of the accuracy curve of the first thickness inversion model and the accuracy curve of the second thickness inversion model is calculated and is used as the thickness threshold.

[0054] The corrected bidirectional reflectance factor corresponding to the thickness threshold in the first thickness inversion model is calculated, which is the first reflectance threshold. The corrected bidirectional reflectance factor corresponding to the thickness threshold in the second thickness inversion model is calculated, which is the second reflectance threshold. .

[0055] Compare the first reflection threshold Second reflection threshold The larger value is used as the reflection threshold. .

[0056] The bidirectional reflectance factor calculated in inversion models for the same thickness may be different. Therefore, this scheme compares the first reflectance threshold. Second reflection threshold A larger value is used as the reflection threshold to avoid thickness inversion errors.

[0057] In some embodiments, the first thickness inversion model is, in denoted as the reflectance of the background water, a as the absorption coefficient, and d as the thickness of the oil film to be inverted. and All of them can be calculated.

[0058] The above inversion method is an improved model of this scheme. The original model is based on the following assumptions: ① the oil film is homogeneous and the surface is smooth. ② multiple scattering and interface reflection effects are ignored. ③ The influence of observation geometry is ignored. The algorithm assumes all measurements and inversions are performed under standard geometric conditions and does not consider the directional reflection characteristics of the oil film surface. When the observation geometry changes, the reflectivity R(k) will change, leading to thickness inversion errors. Therefore, this scheme uses a bidirectional reflectance factor, taking the solar zenith angle, observation zenith angle, and relative azimuth angle as input variables, and corrects and normalizes the bidirectional reflectance factor at any angle to the nadir direction to obtain a corrected bidirectional reflectance factor. This eliminates the influence of angle on the observed spectral data and solves the above problems.

[0059] The second thickness inversion model is , where A0-A4 are the model parameters respectively.

[0060] The original model explicitly states that A0-A4 can only be considered constant when the incident angle remains unchanged; therefore, it explicitly assumes that the model is applicable only under fixed observation geometry conditions. This optimized model, through... Calculating the inversion thickness can solve the above problems.

[0061] In some embodiments, the oil film thickness in each small pool ranges from 0 μm to 500 μm.

[0062] In some embodiments, the radiance acquisition step further includes covering the lens of the hyperspectral imager with a black cloth to acquire dark current data before each data acquisition by the hyperspectral camera, and optimizing the acquisition parameters through the instrument's built-in automatic exposure and focus functions.

[0063] This embodiment uses a configuration of 6 small pools as an example for illustration.

[0064] Oil film samples of varying thicknesses were precisely injected into six small pools. The hyperspectral camera 14 and radiometer 15 were powered on, warmed up, and their functions were checked. Before commencing formal measurements, dark current measurements were performed using a black cloth to eliminate background noise from the instruments. The automated acquisition program was initiated. The hyperspectral camera 14 was set to continuously capture images at ten-second intervals to ensure data capture under different geometric parameters. Simultaneously, the radiometer 15 was set to synchronously record irradiance at a frequency of once per minute. The hyperspectral camera 14 was controlled to move at a uniform speed along the circular guide rail 12. This operation allows for rapid acquisition of a complete circle of observation data covering all relative azimuth angles (0-360°) at each fixed instrument zenith angle. After completing one complete relative azimuth scan, the control program rotated the camera support 13, increasing the observation zenith angle of the hyperspectral camera by 10°. Subsequently, the system repeated a new round of 360° azimuth scanning at the new zenith angle setting. This shooting mode started from a 0° nadir angle and gradually increased to the preset maximum zenith angle. Once the observed zenith angle reaches the preset upper limit of 70°, the control program resets the support angle to 0° and begins a new round of cyclic scanning. This process repeats continuously, with the entire cycle designed to last approximately 10 minutes. The above-mentioned imaging process is synchronized with the natural movement of the sun. From sunrise to sunset, the solar zenith angle and solar azimuth angle continuously change over time. The device's fixed automatic cyclic acquisition mode precisely achieves dense sampling of the entire space observation geometry under different solar positions.

[0065] Example 2: This example proposes an oil film thickness inversion correction method based on the bidirectional reflection characteristics of oil film. The oil film bidirectional reflection characteristics field measurement device described in Example 1 is used. The oil film thickness correction method includes: (11) acquiring spectral data of the target area through remote sensing or telemetry, and calculating the bidirectional reflectance factor of the spectral data. .

[0066] (12) Find the correction factor corresponding to the spectral data through the lookup table. , will the Correction is performed to obtain the corrected bidirectional reflectance factor. .

[0067] (13) When If the thickness of the oil film is not greater than the reflection threshold, the first thickness inversion model is used to invert the thickness of the oil film; otherwise, the second thickness inversion model is used to invert the thickness of the oil film.

[0068] As shown in Figure 7, this method was used to correct the RGB image of the Gulf of Mexico deep-water horizon oil spill event on May 1, 2010, taken by the MISR (Multi-angle Imaging SpectroRadiometer) at a solar zenith angle of 20°. At this time, the spectral data of the AF camera on the MISR with a relative azimuth angle of 129° and an observed zenith angle of 26° were also corrected. It can be seen that the BRF of each band after correction can basically eliminate the influence of angle.

[0069] In some embodiments, the method further includes a step of calculating the amount of oil spill based on the calculated oil spill thickness and oil spill area.

[0070] In some embodiments, the method for calculating the oil spill volume is as follows: .

[0071] Where s is the area corresponding to one pixel. This represents the thickness of the oil spill at sea corresponding to the i-th pixel, and n is the total number of oil spill pixels.

[0072] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A field measurement device for the bidirectional reflection characteristics of an oil film, characterized in that, include: The experimental pool contained a sample of oil and water mixture. A circular guide rail is provided around the experimental water tank. A camera bracket, slidably mounted on the annular guide rail, has a fixed base at its upper end capable of rotating around a horizontal and vertical axis. A hyperspectral camera, fixed to the fixed base, has its lens facing the experimental water tank. The hyperspectral camera's spectral range covers the visible to near-infrared band and is used to measure the radiance of the oil film in the experimental water tank. An irradiance meter is used to measure the irradiance of sunlight. 。 2. The field measurement device for bidirectional reflection characteristics of oil film according to claim 1, characterized in that, The measurement method of the field measurement device for the bidirectional reflection characteristics of the oil film includes: a radiance acquisition step, in which the camera bracket is controlled to slide at least one revolution along the annular guide rail to adjust the observation azimuth angle of the hyperspectral camera, and the hyperspectral camera acquires radiance at a set frequency. Simultaneously acquire the observation azimuth angle of the hyperspectral camera. And observing the zenith angle Rotate the fixed base about the horizontal axis and adjust the observation zenith angle of the hyperspectral camera according to the set step size. Repeat the radiance acquisition steps until all preset observation zenith angles for radiance acquisition are completed; calculate the corresponding solar zenith angle based on the radiance acquisition time and geographical latitude and longitude. and solar azimuth ; Calculate in angle Bidirectional reflectance factor below: Where λ is the wavelength of the collected light. For parameters The radiance collected below, For parameters The irradiance collected below; calculate each With corrected bidirectional reflectance factor The conversion coefficients between them are used to obtain the correction factor. Construct an angle-correction factor lookup table, wherein the angle includes ;in, To observe the zenith angle bidirectional reflectance at time 。 3. The field measurement device for bidirectional reflection characteristics of oil film according to claim 2, characterized in that, The experimental water tank is divided into several independent smaller tanks by internal partitions. Each smaller tank contains oil-water mixture samples with different oil film thicknesses. Where i represents the number of the pool and is a positive integer, the thickness of the oil film in the pool increases with the increase of i; the measurement method of the field measurement device for the bidirectional reflection characteristics of the oil film also includes the step of determining the reflection threshold. In the actual inversion correction, when the correction bidirectional reflection factor is not greater than the reflection threshold, the thickness of the oil film is inverted using the first thickness inversion model; otherwise, the thickness of the oil film is inverted using the second thickness inversion model. The first thickness inversion model is a model based on Beer-Lambert's law, and the second thickness inversion model is a two-beam interference model.

4. The field measurement device for bidirectional reflection characteristics of oil film according to claim 3, characterized in that, The steps for determining the reflection threshold include: calculating the thickness of the oil film in each small pool using the first thickness inversion model, and obtaining... And by using the second thickness inversion model to calculate the thickness of the oil film in each small pool, the following results were obtained. ;according to calculate The inversion accuracy, fitting out The inversion accuracy curve is the accuracy curve of the first thickness inversion model, and based on... calculate The inversion accuracy, fitting out The inversion accuracy curve is the accuracy curve of the second thickness inversion model; the thickness value corresponding to the intersection of the accuracy curves of the first and second thickness inversion models is calculated as the thickness threshold; the corrected bidirectional reflectance factor corresponding to the thickness threshold in the first thickness inversion model is calculated as the first reflectance threshold. The corrected bidirectional reflectance factor corresponding to the thickness threshold in the second thickness inversion model is calculated, which is the second reflectance threshold. Compare the first reflection threshold Second reflection threshold The larger value is used as the reflection threshold. 。 5. The field measurement device for bidirectional reflection characteristics of oil film according to claim 4, characterized in that, The first thickness inversion model is ,in Let 'a' be the reflectance of the background water, 'a' be the absorption coefficient, and 'd' be the oil film thickness to be inverted; the second thickness inversion model is... , where A0-A4 are the model parameters respectively.

6. The field measurement device for bidirectional reflection characteristics of oil film according to claim 3, characterized in that, The oil film thickness in each small pool ranges from 0 μm to 500 μm.

7. The field measurement device for bidirectional reflection characteristics of oil film according to claim 2, characterized in that, The radiance acquisition step also includes covering the lens of the hyperspectral imager with a black cloth to acquire dark current data before each data acquisition by the hyperspectral camera, and optimizing the acquisition parameters through the instrument's built-in automatic exposure and focus functions.

8. A method for inverting and correcting oil film thickness based on the bidirectional reflection characteristics of oil film, characterized in that, Based on the field measurement device for bidirectional reflectance characteristics of oil film described in claim 3, the oil film thickness correction method includes: (11) acquiring spectral data of the target area through remote sensing or telemetry, and calculating the bidirectional reflectance factor of the spectral data. (12) Find the correction factor corresponding to the spectral data through the lookup table. , will the Correction is performed to obtain the corrected bidirectional reflectance factor. (13) When If the thickness of the oil film is not greater than the reflection threshold, the first thickness inversion model is used to invert the thickness of the oil film; otherwise, the second thickness inversion model is used to invert the thickness of the oil film.

9. The oil film thickness inversion correction method according to claim 8, characterized in that, It also includes the step of calculating the amount of oil spill based on the calculated oil spill thickness and oil spill area.

10. The oil film thickness inversion correction method according to claim 9, characterized in that, The method for calculating the amount of oil spill is as follows: ;in, s is the area corresponding to one pixel. This represents the thickness of the oil spill at sea corresponding to the i-th pixel, and n is the total number of oil spill pixels.

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