Method for quickly updating water depth of many-source sounding grid

Abstract

The invention discloses a method for quickly updating the water depth of a crowd-source sounding grid. The method is used for quickly screening and updating crowd-source sounding data with uneven quality levels. The method comprises the following steps: performing quality screening and water depth thinning on sparse and non-uniform crowd-source sounding data by utilizing water depth data acquired by a commercial ship sailing in a port entering channel by using own equipment, outputting uniformly distributed grid water depths, and realizing rapid real-time updating of the crowd-source sounding grid water depths. The problems that a traditional interpolation method is large in calculation amount and slow in data updating are solved.

Description

Technical Field

[0001] The invention belongs to the field of ocean surveying and mapping, and in particular relates to a method for quickly updating water depth of a multi-source bathymetric grid. Background Art

[0002] Crowdsoured bathymetry refers to the process of merchant ships using their own equipment to collect water depths while sailing at sea, and transmitting the recorded water depth data to the data processing center through the network to make up for the lack of existing water depth data. Merchant ship tracks are lines along the waterway. The overlapping lines of multiple merchant ships will inevitably generate a large amount of redundant data. In the port approach channel section, the final result of crowdsouring is a uniformly distributed grid water depth covering the entire waterway. It is necessary to merge and select the water depths from a large number of merchant ships, and convert the sparse and uneven discrete point water depths into uniformly distributed grid water depths.

[0003] Interpolation is used to convert discrete point water depth to grid water depth. Common interpolation methods include Kriging, Inversed Distance Weighted, Triangulation with Linear Interpolation, Local Polynomial, Spline, Nature Neighbor Interpolation, etc., which are suitable for different scenarios. However, there are two common shortcomings. One is that the quality difference between data is not taken into account, and the other is that the interpolation calculation is time-consuming and does not meet the needs of real-time data update. The collectors of multi-source bathymetric data are non-professional bathymetric personnel, and the data quality is unpredictable. The accuracy of bathymetric data from different merchant ships varies greatly. When interpolating water depth grids, it is unreasonable to treat all bathymetric data equally. One of the advantages of crowd-source bathymetry is the large amount of data and fast update speed. Every few minutes, a merchant ship passes by and the bathymetry data in the channel is updated. Taking the 92km long and 400m wide Yangtze River Estuary deep-water channel as an example, every time a merchant ship data is received, the 92km*0.4km channel area must be interpolated once. The calculation is huge and time-consuming, and it is impossible to achieve high-frequency updates at the minute level. Summary of the invention

[0004] Based on this, the purpose of the present invention is to provide a method for quickly updating the multi-source bathymetric grid water depth, and to quickly screen and update the multi-source bathymetric data with uneven quality levels. The water depth data collected by merchant ships sailing in the port approach channel using their own equipment is used to screen the quality and extract the water depth of the sparse and uneven multi-source bathymetric data, and output a uniformly distributed grid water depth, so as to achieve a fast and real-time update of the multi-source bathymetric grid water depth. This solves the problem of large calculation amount and slow data update of the traditional interpolation method.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A method for rapidly updating multi-source bathymetric grid water depths utilizes the equipment owned by merchant ships sailing in harbors and waterways to collect water depth data of target waters, performs quality screening and water depth thinning on sparse and uneven multi-source bathymetric data, outputs uniformly distributed grid water depths, and realizes rapid real-time updating of multi-source bathymetric grid water depths.

[0007] Optionally, the specific implementation steps include:

[0008] (1) Divide the target water area into square grids, with one grid representing one water depth point on the map. The specification stipulates that the maximum scale of the basic waterway map is 1:2000 and the minimum spacing of water depth points on the map is 5 mm. Based on this requirement, the grid size is calculated to be 10m*10m.

[0009] (2) Before each target merchant ship is connected to the data collection grid depth, the trustworthiness of the merchant ship's depth data is evaluated based on the ship's hardware conditions, the performance and installation of the depth sounding equipment, and the accuracy of the main parameter settings (such as the eccentricity of the depth sounder positioner, draft, speed of sound, etc.) and the score is assigned from 0 to 100. The evaluation value of each dimension is expressed as the credibility T i Indicates that the reliability T i Reflects the difference in accuracy of bathymetric data of different merchant ships. A higher value indicates higher data accuracy.

[0010] The evaluation values ​​of each dimension are evaluated separately and then summarized into a total metadata credibility T 元 , as listed below:

[0011]

[0012] (3) Determine the number of sample water depths n for each grid and take it as 12;

[0013] (4) The water depth of all merchant ships in the same grid is weighted averaged to obtain the water depth value of the grid. The water depths of all merchant ships in the same grid are h1, h2, …, h n , the credibility is T 元1 ,T 元2 ,…,T 元n, n is 12, and the water depth h of the grid is calculated according to the following formula:

[0014]

[0015] (5) Delete all water depths in the grid, record the water depth at the center of the grid as h, and the data in the grid is cleaned to obtain the grid water depth. All other grids are processed in the same way.

[0016] Optionally, in step (3), considering that as the number of water depths increases, the impact of the subsequent additional water depths on the final grid water depth becomes smaller and smaller, which is not conducive to reflecting the short-term scouring and silting changes of the waterway depth, it is necessary to determine the appropriate number of water depths involved in the calculation in the grid and introduce the mean error calculation formula as follows:

[0017]

[0018] In the formula, m is the error in the observed value, m L is the error in the mean, n is the number of samples;

[0019] say is the error coefficient in the mean value. The precision of the mean value increases with the increase of the number of samples. When the number of samples is less than 12, the precision of the mean value increases significantly with the number of samples. The number of sample water depths n is 12;

[0020] In order to maintain the independence of the data, the 12 water depth data should come from different merchant ships respectively. For multiple voyage data of the same merchant ship, only the latest one will be used for calculation.

[0021] Furthermore, when a new merchant ship enters the waterway and sails through a grid, a new water depth is included in the grid, the water depth of the earliest merchant ship is eliminated, the sample number 12 is kept unchanged, and the data update of the grid is recalculated.

[0022] Due to the adoption of the above technical scheme, the beneficial effects of the present invention include: the grid water depth interpolation range is reduced from the entire data-covered water area to a single grid, with small calculation amount and fast calculation speed; data quality attributes are considered during water depth interpolation, and different credibility evaluation values ​​are assigned to merchant ship bathymetric data of different qualities, thereby improving the accuracy of grid water depth; only the grid water depth through which the merchant ship sails is updated, thereby realizing rapid and timely updating of bathymetric data and ensuring the advantages of multi-source bathymetric sounding. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the water depth grid of the present invention.

[0024] Figure 2 This is a plot of the relationship between mean precision and sample size. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0026] The merchant ship track is a line. Only the area where the route passes is updated. The data outside the track is maintained in the original version. Updating along the track will greatly reduce the amount of calculation, and basically synchronize data update and navigation. The method for determining the grid water depth is to take the weighted average of the water depths of a certain number of merchant ships in the grid, and the weight is the credibility of each merchant ship.

[0027] The specific implementation steps are as follows:

[0028] (1) Divide the target water area into square grids, with one grid representing one water depth point on the map. The specification stipulates that the maximum scale of the basic waterway map is 1:2000 and the minimum spacing of water depth points on the map is 5 mm. Based on this requirement, the grid size is calculated to be 10m*10m.

[0029] (2) Before each target merchant ship is connected to the data collection grid water depth, the trustworthiness of the merchant ship's bathymetric data is evaluated based on the ship's hardware conditions, the performance and installation of the bathymetric equipment, and the accuracy of the main parameter settings. The evaluation value of each dimension is expressed as the credibility T i Indicates that the reliability T i Reflects the difference in accuracy of bathymetric data of different merchant ships. A higher value indicates higher data accuracy.

[0030] The evaluation values ​​of each dimension are evaluated separately and then summarized into a total metadata credibility T 元 , as listed below:

[0031]

[0032] The following are the contents of the credibility dimension evaluation and the scoring rules:

[0033] Table 1 Credibility evaluation indicators

[0034] Serial number Metadata for credibility assessment Evaluation Rules Remark 1 Vessel length 30-100 minutes The bigger the higher the score 2 Nominal accuracy of depth sounder 30-100 minutes The higher the accuracy, the higher the score 3 Positioner nominal accuracy 30-100 minutes The higher the accuracy, the higher the score 4 Equipment life 30-100 minutes The shorter the term, the higher the score 5 Depth Sounder Draught Uncertainty 0 / 100 points 100 points for setting, 0 points for not setting 6 GNSS eccentricity 0 / 100 points 100 points for setting, 0 points for not setting 7 Technical staff comments 0~100 points Comprehensive evaluation based on other factors

[0035] The scoring rules corresponding to the above table are as follows:

[0036] 1) The length of a ship is closely related to its navigation stability and wind and wave resistance. The larger the size and displacement, the more stable the ship's navigation and the stronger its wind and wave resistance. When the length is greater than the wavelength, the ship's attitude has little effect. The smaller the length, the greater the impact of the attitude. The impact is greatest when the length is equal to 1 / 3 of the wavelength. The Shanghai Port approach channel and the waters within the port are dominated by wind and waves with a wavelength of less than 100 meters. Therefore, it is stipulated that ships with a length of 100 meters or more will get 100 points, and ships with a length of 20 meters or less will get 30 points.

[0037] 2) Nominal accuracy of depth sounder: expressed as the depth error The unit is m, A (m) is the fixed error, B (1%) is the proportional error, and d (m) is the measured water depth of 20m. According to the technical indicators of the depth sounder in Table 1, the professional-grade Haiying HY1600 has the highest accuracy (σ = 0.022) and a full score of 100 points, and the lowest accuracy is (σ = 0.500) and below is 30 points.

[0038] 3) Positioner nominal accuracy: expressed as the positioning error The unit is m, A(m) is the fixed error, B(10 -3 ) is the proportional error, d (km) is the distance to the differential station, which is 200km (the 200km range of the Dajishan beacon differential station basically covers the waters of Shanghai Port). The professional-grade Trimble SPS855 DGPS mode has the highest accuracy (σ=0.320) and a full score of 100 points, and the lowest accuracy (σ=10.000) and below has a score of 30 points.

[0039] 4) Equipment age: As the age of equipment increases, its performance and stability decrease. Age also reflects the newness of the equipment. Based on a depreciation period of 10 years, the score is 10 minus the age multiplied by 10. The average of the depth sounder and the locator is calculated separately, with a maximum score of 100 and a minimum score of 30.

[0040] 5) Echo sounder draft uncertainty: The draft of a ship may be affected by cargo, fuel or other factors. The echo sounder draft uncertainty is the accuracy of the change in the draft value. Data contributors provide these estimates when collecting data to help correctly estimate the depth of the echo sounder sensor below the waterline. If the echo sounder draft uncertainty is not set (Null), 0 points will be awarded. If it is set, 100 points will be awarded.

[0041] 6) GNSS eccentricity: GNSS eccentricity indicates the longitudinal and lateral offset of the GNSS receiver antenna relative to the depth sounder transducer in the hull coordinate system. The center of the hull coordinate system is generally set to the depth sounder transducer, with the horizontal axis pointing to the starboard side and the vertical axis parallel to the bow. A more accurate value can be obtained by measuring the ship before it leaves the factory. If the eccentricity is not set (Null), 0 points will be given, and if it is set, 100 points will be given.

[0042] 7) Technical staff comments: The technical staff will make a comprehensive judgment based on the ship's condition, equipment advancement, whether the equipment is installed in a standardized manner, depth sounder draft and GNSS eccentricity measurement accuracy, metadata integrity, and ship management level, with a score of 0 to 100.

[0043] The evaluation values ​​of each dimension are evaluated separately and then summarized into a total metadata credibility T 元 (0 to 100 points), as listed below:

[0044]

[0045] (3) Determination of the number of sample water depths n: Considering that as the number of water depths increases, the impact of the subsequent additional water depths on the final grid water depth becomes smaller and smaller, which is not conducive to reflecting the short-term scouring and silting changes of the waterway depth, it is necessary to determine the appropriate number of water depths involved in the calculation within the grid. Introduce the calculation formula for the mean error,

[0046]

[0047] In the formula, m is the error in the observed value, m L is the error in the mean, and n is the number of samples.

[0048] say is the error coefficient in the mean, and its relationship with sample size is shown below Figure 2 :

[0049] The number of sample water depths is the sampling points of a grid. It is to take the latest 12 water depth points from different merchant ships in chronological order, that is, take the latest 12 water depth points of merchant ships;

[0050] A large number of merchant ships are sailing in the waterway day and night. As time goes on, the number of water depth points falling into the grid continues to accumulate, and the number is increasing, and the time span is getting longer and longer. In order to reflect short-term terrain changes, a grid only takes the 12 most recent water depth points to participate in the calculation. According to the current ship flow in the Yangtze River Estuary waterway, the sample water depth in the grid is updated in about 1-2 days. The purpose of this is to reflect the changes in the waterway terrain within 1-2 days, reflecting the advantage of fast update of multi-source bathymetric data.

[0051] As can be seen from the figure, the accuracy of the average value increases with the increase of the number of samples. When the number of samples is less than 12, the accuracy of the average value increases significantly with the number of samples. When the number of samples is more than 12, the improvement of the accuracy of the average value is not obvious. Therefore, the number of sample water depths n is taken as 12. In order to maintain the independence of the data, the 12 water depth data should come from different merchant ships, and for the multiple voyage data of the same merchant ship, only the latest one is taken for calculation.

[0052] (4) The water depth of all merchant ships in the same grid is weighted averaged to obtain the water depth value of the grid. The water depths of all merchant ships in the same grid are h1, h2, …, h n , the credibility is T 元1 ,T 元2 ,…,T 元n , n is 12, and the water depth h of the grid is calculated according to the following formula:

[0053]

[0054] (5) Delete all water depths in the grid, record the water depth at the center of the grid as h, and the data in the grid is cleaned to obtain the grid water depth. All other grids are processed in the same way.

[0055] (6) When a new merchant ship enters the waterway and passes through a grid, a new water depth is included in the grid, the earliest water depth is eliminated, the sample number 12 is kept unchanged, and the data update of the grid is recalculated.

[0056] The above-mentioned related explanations and descriptions of the embodiments are for the convenience of those skilled in the art to understand and apply the present invention. It is obvious that those familiar with the art can easily make various modifications to these contents and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above-mentioned related explanations and descriptions of the embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for fast updating water depth of multi-source bathymetric grid, characterized in that: The merchant ships sailing in the port channel use their own equipment to collect the water depth data of their target waters, and the sparse and uneven multi-source bathymetric data are screened for quality and the water depth is thinned out. The evenly distributed grid water depth is output, and the multi-source bathymetric grid water depth is quickly updated in real time.

2. The method for rapidly updating water depth of multi-source bathymetric grid according to claim 1, characterized in that: The specific implementation steps include: (1) Divide the target water area into square grids, with one grid representing one water depth point on the map. The specification stipulates that the maximum scale of the basic waterway map is 1:2000 and the minimum spacing of water depth points on the map is 5 mm. Based on this requirement, the grid size is calculated to be 10m*10m. (2) Before each target merchant ship is connected to the data collection grid water depth, the trustworthiness of the merchant ship's bathymetric data is evaluated based on the ship's hardware conditions, the performance and installation of the bathymetric equipment, and the accuracy of the main parameter settings. The evaluation value of each dimension is expressed as the credibility T i Indicates that the reliability T i Reflects the difference in accuracy of bathymetric data of different merchant ships. A higher value indicates higher data accuracy. The evaluation values ​​of each dimension are evaluated separately and then summarized into a total metadata credibility T 元 , as listed below: (3) Determine the number of sample water depths n for each grid and take it as 12; (4) The water depth of all merchant ships in the same grid is weighted averaged to obtain the water depth value of the grid. The water depths of all merchant ships in the same grid are h1, h2, …, h n , the credibility is T 元1 ,T 元2 ,…,T 元n , n is 12, and the water depth h of the grid is calculated according to the following formula: (5) Delete all water depths in the grid, record the water depth at the center of the grid as h, and the data in the grid is cleaned to obtain the grid water depth. All other grids are processed in the same way.

3. The method for fast updating water depth of multi-source bathymetric grid according to claim 2, characterized in that: In step (3), considering that as the number of water depths increases, the impact of the subsequent additional water depths on the final grid water depth becomes smaller and smaller, which is not conducive to reflecting the short-term scouring and silting changes of the waterway depth, it is necessary to determine the appropriate number of water depths involved in the calculation in the grid and introduce the calculation formula for the mean error, as follows: In the formula, m is the error in the observed value, m L is the error in the mean, n is the number of samples; say is the error coefficient in the mean value. The precision of the mean value increases with the increase of the number of samples. When the number of samples is less than 12, the precision of the mean value increases significantly with the number of samples. The number of sample water depths n is 12; In order to maintain the independence of the data, the 12 water depth data should come from different merchant ships respectively. For multiple voyage data of the same merchant ship, only the latest one will be used for calculation.

4. The method for fast updating water depth of multi-source bathymetric grid according to claim 3 is characterized in that: When a new merchant ship enters the waterway and passes through a grid, a new water depth is included in the grid, the water depth of the earliest merchant ship is eliminated, the sample number 12 is kept unchanged, and the data update of the grid is recalculated.

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