A video geolocation tracing method based on the dynamic variation law of solar shadow length

Abstract

This invention discloses a video geolocation tracing method based on the dynamic variation law of solar shadow length, belonging to the field of geographic information positioning technology. The method takes a video stream containing a fixed vertical pole and the shooting time as input, obtains the shadow length sequence, initializes parameters to set the search range, constructs a shadow length model integrating solar declination angle, hour angle, and altitude angle, constructs a multi-objective optimization function, and uses an intelligent algorithm to find the optimal solution. Finally, it outputs the latitude and longitude of the shooting location, the height of the vertical pole, and an error analysis report. This invention solves the problems of poor adaptability, low accuracy, and low efficiency of traditional technologies through multi-parameter coupled modeling, and can achieve video geolocation tracing in GPS-restricted scenarios.

Description

Technical Field

[0001] This invention belongs to the field of geographic information positioning and video source tracing technology, and relates to a video geographic location tracing method based on the dynamic change law of the sun's shadow length. Background Technology

[0002] With the rapid development of Geographic Information System (GIS) technology and the widespread application of big data analytics in various fields, video data is playing an increasingly important role. However, key information such as the shooting location and time of video data is often missing or maliciously tampered with, posing a dual challenge to the verification of video data sources and its effective utilization, severely restricting the reliable application of video data in critical areas.

[0003] To address these issues, solar shadow positioning technology has emerged. This technology infers the location and date of a video's recording by analyzing changes in the sun's shadow cast by objects in the video. Utilizing this natural physical characteristic of the sun's shadow, it achieves passive positioning and boasts significant advantages such as resistance to interference and spoofability, providing reliable positioning capabilities even in scenarios where GPS positioning is limited.

[0004] However, most existing solar shadow positioning technologies suffer from poor model adaptability, failing to flexibly adapt to different shooting scenarios and parameter conditions; insufficient analysis of the coupling relationships between various parameters leads to limited model calculation accuracy; and limited positioning accuracy in practical applications makes it difficult to meet high-precision positioning requirements. Therefore, there is an urgent need to construct a systematic and accurate multi-parameter coupling model and corresponding analysis framework to improve the practicality and accuracy of solar shadow positioning technology. Summary of the Invention

[0005] The purpose of this invention is to provide a video geolocation tracing method based on the dynamic variation law of the sun's shadow length. By constructing a multi-parameter coupled shadow length calculation model and combining it with an intelligent optimization algorithm, the method can ultimately achieve accurate positioning of the video shooting location.

[0006] This invention is achieved through the following technical solution: A video geolocation tracing method based on the dynamic variation of solar shadow length includes the following steps: Step 1: Obtain the video stream containing the fixed straight rod object and the corresponding shooting time data, and perform data preprocessing; Step 2: Calculate the solar declination angle Solar hour angle and solar altitude angle Finally, a shadow length calculation model is constructed; Step 3: Construct a multi-objective optimization function that minimizes the sum of the absolute errors between the actual shadow length and the theoretical shadow length; Step 4: Use an intelligent optimization algorithm to solve the optimization function and output the latitude, longitude and the height of the straight rod when the error is minimized; Step 5: Generate standardized results including the latitude and longitude of the shooting location, the optimal solution for the height of the straight pole, and an error analysis report.

[0007] The present invention also has the following technical features: Preferably, the data preprocessing described in step one includes: Video keyframes are extracted according to a preset step size, and the physical coordinates of the bottom of the straight rod and the top of the shadow are obtained through image recognition technology to calculate the actual shadow length sequence. Calculate the accumulated day and day angle based on the shooting date, and set the search range and step size for longitude, latitude, and pole height.

[0008] Preferably, the solar declination angle mentioned in step two The formula is expressed as: in The angle of the sun is calculated using the following formula: In the formula For accumulated days.

[0009] Preferably, the solar hour angle mentioned in step two The calculation formula is: In the formula, Solar hour angle, It is the local true solar time. For local mean solar time, Due to time difference, For local mean solar time, Background time, This is the reference for the mean solar time offset corresponding to Beijing time. The longitude of the shooting location. This is the conversion of longitude to minutes and seconds. It is the sun's horn.

[0010] Preferably, the solar altitude angle mentioned in step two The calculation formula is: In the formula, Represents the latitude of the observation point.

[0011] Preferably, the formula for calculating the shadow length in step two is: in, This represents the height of the straight rod.

[0012] Preferably, the calculation formula for the multi-objective optimization function mentioned in step three is as follows: In the formula, The latitude of the shooting location. For the first i The actual shadow length at each point in time Let be the theoretical shadow length at the i-th time point. m The total number of data points representing the shadow length.

[0013] Preferably, the intelligent optimization algorithm described in step four is a genetic algorithm or a particle swarm optimization algorithm, with a search step size of 0.01 and a convergence threshold of 0.01 meters.

[0014] Compared with the prior art, the present invention has the following technical effects: This invention breaks through the limitations of traditional technologies that focus on a single parameter, and constructs a full-chain mathematical model of "solar motion - spatiotemporal parameters - shadow length". It integrates multiple parameters such as solar declination angle, hour angle, and altitude angle, quantifies the coupling effect between parameters, and improves the model's adaptability and calculation accuracy. This invention combines a dual support system of "basic model + rule library", narrows the parameter search space by the variation of shadow length with latitude and time, and then uses intelligent algorithms such as particle swarm optimization and genetics to quickly find the optimal solution and improve computational efficiency. The calculation process of this invention is based on mature theories of astronomy and geometry. Each parameter derivation has a clear physical meaning. The results include error analysis and confidence assessment. The output latitude and longitude coordinates, rod height and error distribution can be cross-verified, and the reliability is high. Attached Figure Description

[0015] Figure 1 Solar altitude angle Schematic diagram; Figure 2 Solar declination angle Schematic diagram; Figure 3 Schematic diagrams of the sun's shadow: (a) a three-dimensional schematic diagram of the sun's shadow; (b) a two-dimensional schematic diagram of the sun's shadow. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0017] This embodiment presents a video-based geographic location tracing method based on the dynamic variation of solar shadow length. Taking a 3-meter-high vertical pole at Tiananmen Square (39°54′26″N, 116°23′29″E) as an example, the method calculates and plots the curve of shadow length variation over time, revealing the dynamic evolution of shadow length under specific spatiotemporal conditions. The method includes the following steps: Step 1: Obtain the video stream containing the fixed straight rod object and the corresponding shooting time data, and perform data preprocessing; Video stream data: must contain the fixed straight rod object, the image must be clear and unobstructed, the straight rod must not move during the shooting process, the frame rate must be no less than 24 frames / second, and the extraction of shadow vertex coordinates within a continuous time period is supported.

[0018] Shooting time: must be accurate to the hour. If there are time zone differences, they must be converted to Beijing time. In this example, the shooting time was from 9:00 to 15:00 on October 22, 2015.

[0019] Data preprocessing includes: Video keyframes are extracted at preset step sizes. Image recognition technology is used to obtain the physical coordinates of the bottom of the pole and the apex of its shadow, and the actual shadow length sequence is calculated. Keyframes (9:00, 9:06, ..., 15:00) are extracted from the input video stream at 6-minute step sizes, totaling 61 frames, ensuring coverage of the complete observation period. Shadow apex coordinates are obtained: Image recognition technology (such as edge detection and threshold segmentation) is used to locate the bottom of the pole (origin) in each frame. ) and shadow vertices ( The pixel coordinates of a point are combined with video shooting parameters (such as lens focal length and shooting distance) to convert them into actual physical coordinates (unit: meters); based on the origin... With vertex The physical coordinates are used to calculate the actual shadow length for each frame using the Euclidean distance formula. This forms a length sequence (61 data points in total). Calculate the accumulated day and day angle based on the shooting date, and set the search range and step size for longitude, latitude, and pole height.

[0020] The cumulative day parameter is determined as follows: 2015 was a common year (365 days), and the cumulative day for October 22nd is... =295 days, calculate the solar angle .

[0021] Search range setting: Longitude ,latitude Straight rod height Meters (fixed in this embodiment) =3 meters), and the search step size is set to 0.01 (to improve the solution accuracy).

[0022] Step 2: Calculate the solar declination angle Solar hour angle and solar altitude angle Finally, a shadow length calculation model is constructed; According to Spencer's algorithm, the solar declination angle The formula is expressed as: in The angle of the sun is calculated using the following formula: In the formula The cumulative day, i.e., the sequential number of the date within the year, such as January 1st as 1; January 5th as 5; December 31st as 365, and 366 in a leap year; solar declination angle. δ From [1] to ,like Figure 2 As shown. At the spring and autumn equinoxes, the sun's declination is zero, and at this time, the sun's rays shine directly on the Earth's equator; at the summer solstice (the beginning of summer in the Northern Hemisphere), the sun's declination reaches its maximum value. At the winter solstice (the beginning of winter in the Northern Hemisphere), the sun's declination angle reaches its minimum. .

[0023] Solar hour angle The calculation formula is: In the formula, The solar hour angle, its range is from arrive ; It is the local true solar time. For local mean solar time, Due to time difference, For local mean solar time, Background time, This is the reference for the mean solar time offset corresponding to Beijing time. The longitude of the shooting location. This is the conversion of longitude to minutes and seconds. It is the sun's horn.

[0024] Solar altitude angle The calculation formula is: In the formula, Represents the latitude of the observation point. Solar altitude angle. The range of values ​​is arrive ,like Figure 1 As shown, at a specific latitude and longitude, the solar altitude angle reaches its maximum at noon. At this time, the sun is at its highest point at the observation point; it reaches its minimum value at sunrise and sunset. At this time, the sun is located on the horizon at the observation point.

[0025] Taking the bottom end of the fixed straight rod as the origin Set westward along the latitude line x The positive direction of the axis, along the meridian northwards, is designated as... y The positive direction of the axis, upward along the straight rod, is set as... z Establish a spatial rectangular coordinate system along the positive axis. The height of the fixed rod is... The length of the shadow is ,like Figure 3 As shown. Combined with Figure 3 Using relevant trigonometric function formulas in analytic geometry, the formula for calculating the shadow length is derived as follows: in, This represents the height of the straight rod.

[0026] Step 3: Construct a multi-objective optimization function that minimizes the sum of the absolute errors between the actual shadow length and the theoretical shadow length. The calculation formula is as follows: In the formula, The latitude of the shooting location. Let be the actual shadow length at time point i. For the first i The theoretical shadow length at a given time point m The total number of data points representing the shadow length.

[0027] Step 4: Use an intelligent optimization algorithm to solve the optimization function and output the latitude, longitude and height of the straight pole corresponding to the minimum error; the intelligent optimization algorithm is a genetic algorithm or a particle swarm optimization algorithm, with a search step size of 0.01 and a convergence threshold of 0.01 meters; The genetic algorithm iterates through all combinations of "latitude + pole height" (e.g., latitude 30°N~35°N, height 1.5m~1.8m, step size 0.01), calculates the value for each combination, and finally selects the smallest value. The parameter corresponding to the value is taken as the optimal solution: In this embodiment =0.13 meters, which meets the accuracy requirement of "convergence threshold of 0.01 meters".

[0028] Step 5: Generate standardized results including the latitude and longitude of the shooting location, the optimal solution for the height of the straight pole, and an error analysis report.

[0029] The corresponding optimal parameters are latitude 32.00°N, longitude 116.30°E, and straight rod height 1.6m. The error distribution at each time point is 10:00 (0m), 11:00 (0.01m), 12:00 (0.08m), 13:00 (0.02m), and 14:00 (0.02m).

Claims

1. A video geolocation tracing method based on the dynamic variation law of solar shadow length, characterized in that, Includes the following steps: Step 1: Obtain the video stream containing the fixed straight rod object and the corresponding shooting time data, and perform data preprocessing; Step 2: Calculate the solar declination angle Solar hour angle and solar altitude angle Finally, a shadow length calculation model is constructed; Step 3: Construct a multi-objective optimization function that minimizes the sum of the absolute errors between the actual shadow length and the theoretical shadow length; Step 4: Use an intelligent optimization algorithm to solve the optimization function and output the latitude, longitude and the height of the straight rod when the error is minimized; Step 5: Generate standardized results including the latitude and longitude of the shooting location, the optimal solution for the height of the straight pole, and an error analysis report.

2. The video geographic location tracing method based on the dynamic variation law of solar shadow length according to claim 1, characterized in that, The data preprocessing described in step one includes: Video keyframes are extracted according to a preset step size, and the physical coordinates of the bottom of the straight rod and the top of the shadow are obtained through image recognition technology to calculate the actual shadow length sequence. Calculate the accumulated day and day angle based on the shooting date, and set the search range and step size for longitude, latitude, and pole height.

3. The video geographic location tracing method based on the dynamic variation law of solar shadow length according to claim 1, characterized in that, The solar declination angle mentioned in step two The formula is expressed as: in The angle of the sun is calculated using the following formula: In the formula For accumulated days.

4. The video geographic location tracing method based on the dynamic variation law of solar shadow length according to claim 1, characterized in that, The solar hour angle mentioned in step two The calculation formula is: In the formula, Solar hour angle, It is the local true solar time. For local mean solar time, Due to time difference, For local mean solar time, Background time, This is the reference for the mean solar time offset corresponding to Beijing time. The longitude of the shooting location. This is the conversion of longitude to minutes and seconds. It is the sun's horn.

5. The video geographic location tracing method based on the dynamic variation law of solar shadow length according to claim 1, characterized in that, The solar altitude angle mentioned in step two The calculation formula is: In the formula, Represents the latitude of the observation point.

6. The video geographic location tracing method based on the dynamic variation law of solar shadow length according to claim 1, characterized in that, The formula for calculating the shadow length mentioned in step two is: in, This represents the height of the straight rod.

7. The video geographic location tracing method based on the dynamic variation law of solar shadow length according to claim 1, characterized in that, The formula for calculating the multi-objective optimization function mentioned in step three is as follows: In the formula, The latitude of the shooting location. Let be the actual shadow length at time point i. Let be the theoretical shadow length at the i-th time point. m The total number of data points representing the shadow length.

8. The video geographic location tracing method based on the dynamic variation law of solar shadow length according to claim 1, characterized in that, The intelligent optimization algorithm described in step four is a genetic algorithm or a particle swarm optimization algorithm, with a search step size of 0.01 and a convergence threshold of 0.01 meters.

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