Many-source sounding data instrument correction method based on large-scale nautical chart

Abstract

The invention provides a mass-source sounding data instrument correction method based on a large-scale nautical chart, and belongs to the technical field of marine surveying and mapping. Comprises: inputting geographic coordinates of a current position of a ship; finding out a sea chart with the maximum scale containing the position; according to a Mercator projection positive solution formula, calculating on-chart coordinates of the current position of the ship on the nautical chart; the method comprises the following steps: constructing a sea chart water depth triangulation network, and calculating sea chart load water depth at a position on a chart; continuously observing and recording seawater depth values at different moments by using a shipborne acoustic depth finder; synchronously calculating tide values at corresponding moments by using a sea chart tide table; according to the seawater depth values at different moments and the corresponding tide values, the actually measured static water depth is solved; and constructing an error correction model of the crowd-source sounding data instrument according to the sea graph-borne water depth and the actually measured static water depth at the current position of the ship. According to the method, the defect that an existing many-source sounding method lacks instrument system error correction is overcome, the influence of instrument system errors is weakened, and the precision of many-source sounding data is improved.

Description

Technical Field

[0001] This invention belongs to the field of marine surveying and mapping technology, and relates to an instrument correction method based on crowdsourced bathymetry data from large-scale nautical charts. Background Technology

[0002] Crowdsource sounding data refers to water depth data collected by volunteer vessels, not professional surveyors, using onboard sounding equipment and positioning devices during their navigation journeys. To promote the application of crowdsource sounding data in practical production, a series of post-processing steps are required, including corrections for tides, draft, attitude, sound speed, and instrumentation, to improve the accuracy of navigational depth data. Numerous international scholars have conducted related research on data correction in crowdsource sounding.

[0003] Currently, vessels participating in crowdsourced sounding often use low-precision attitude sensors due to cost constraints, which can significantly impact the quality of sounding data. Subsequently, by independently developing cost-effective and easy-to-install attitude sensors, support was provided for attitude correction of crowdsourced sounding data. Simultaneously, the lack of vertical offset between positioning and sounding equipment in crowdsourced sounding directly affects the accuracy of converting water depth data to the reference ellipsoid. Therefore, calibration points were established to obtain relevant parameters for water level correction in tide-free modes, indirectly compensating for the impact of heave and ship draft on sounding data. Subsequent researchers systematically studied the reconstructed sound velocity profile obtained from WOA18 model data and measured temperature and salinity data, demonstrating that fusing temperature and salinity model data can improve the accuracy of sound velocity data, especially overcoming the lack of sound velocity profile data in deep-sea areas. Furthermore, when the sound velocity profile of the measurement area is lacking in crowdsourced sounding, the embedded temperature sensor of the sounding equipment and assumed salinity values ​​can be used to roughly estimate the sound velocity, and the idea of ​​using historical ocean temperature and salinity data for sound velocity correction was proposed. Researchers have also employed two spatiotemporal detection methods for underwater navigational obstruction detection. One approach combines the Local Outlier Factor algorithm and the DBSCAN algorithm to spatially detect anomalous data in crowdsourced bathymetry data, thereby distinguishing navigational obstructions in the temporal domain. The other approach calculates the Local Moran's I and Z-scores in space and then uses frequency domain analysis to identify anomalous data. However, there is currently little research on the systematic error correction issues inherent in bathymetry instruments themselves. Summary of the Invention

[0004] To overcome the current lack of effective instrument correction methods for crowdsourced bathymetry data, this invention proposes an instrument correction method for crowdsourced bathymetry data based on large-scale nautical charts. Existing experiments have shown that the method described in this invention can reduce the influence of instrument system errors and improve the accuracy of crowdsourced bathymetry data.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] An instrument correction method based on crowdsourced bathymetry data from large-scale nautical charts includes the following steps:

[0007] Step S1: When the ship docks at a pier or anchors at a certain location at sea, turn on the ship's satellite navigation and positioning system and record the geographical coordinates of the ship's current position as (B,L);

[0008] Step S2: Locate the largest scale nautical chart that includes the ship's current position;

[0009] Step S3: Calculate the geographic coordinates (B,L) of the ship's current position on the nautical chart and their map coordinates (X,Y) according to the Mercator projection forward formula;

[0010] Step S4: Extract all depth points on the electronic nautical chart to construct a nautical chart depth triangulation network. The triangle where the ship is currently located is T. Extract the map coordinates and depth values ​​of the three vertices of the triangle, and record them as (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3) respectively.

[0011] Step S5: Based on the relative positions of the ship's current position and the three vertices of the triangle (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3), calculate the estimated chart depth of the ship's current position (X, Y) using the linear triangulation method, denoted as Z. Chart ;

[0012] Step S6: Turn on the acoustic depth sounder equipped on board the ship and continuously record the seawater depth values ​​and times observed by the acoustic depth sounder at n consecutive moments. Record the seawater depth values ​​observed at the n consecutive moments as (H1, H2, ..., H...). n The observation times for each observation are (T1, T2, ..., T). n );

[0013] Step S7: Calculate the observation time T for each observation based on the tide table values ​​on the nautical chart or the relevant nautical book for the sea area where the ship is located. i The tidal values ​​for (i = 1, 2, ..., n) are denoted as (Tide1, Tide2, ..., Tide). n );

[0014] Step S8: Based on the continuously observed seawater depth values ​​(H1, H2, ..., H) at n time points n ) and the corresponding tidal values ​​(Tide1, Tide2, ..., Tide) at the time. n ), determine the measured static water depth Z. Survey ;

[0015] Step S9: Estimate the water depth Z based on the chart of the ship's current position. Chart And the measured static water depth Z Survey The instrument correction numerical model for mass source bathymetry data was obtained.

[0016] In step S5, based on the relative positions of the ship's current position and the three vertices of the triangle (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3), the linear interpolation method is used to calculate the estimated chart depth of the ship's current position (X, Y), denoted as Z. Chart Z Chart The calculation formula is:

[0017]

[0018] In step S8, based on the continuously observed seawater depth values ​​(H1, H2, ..., H) at n time points... n ) and the corresponding tidal values ​​(Tide1, Tide2, ..., Tide) at the time. n ), determine the measured static water depth Z. Survey Z Survey The calculation formula is:

[0019]

[0020] In step S9, the estimated water depth Z is based on the nautical chart of the ship's current position. Chart And the measured static water depth Z Survey The instrument correction numerical model for crowdsourced bathymetry data was derived as follows:

[0021]

[0022] Where, ΔZ j This represents the instrument correction value of the mass sounding data at point j. This represents the depth value of the original mass sounding data record for a point j.

[0023] The beneficial effects of this invention are as follows: The instrument correction method proposed in this invention overcomes the deficiency of current crowdsourced sounding methods in lacking instrument system error correction. Existing experiments have shown that the method described in this invention can reduce the influence of instrument system errors and improve the accuracy of crowdsourced sounding data. Attached Figure Description

[0024] Figure 1 This is the overall flowchart of the error correction method for crowdsourced depth sounding instruments described in this invention. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to specific examples and accompanying drawings.

[0026] This invention proposes an instrument correction method for crowdsourced bathymetry data based on large-scale nautical charts. The process involves combining measured surface sound velocity with historical profile sound velocity data to perform sound velocity profile inversion, thereby correcting the sound velocity in the water depth data. Suppose we need to obtain sound velocity profile data from station A for sound velocity correction of the water depth data. Using the method described in this invention, this embodiment includes the following steps (e.g.) Figure 1 As shown):

[0027] Step S1: The ship is anchored at sea, and the current geographic coordinates of the shipborne satellite navigation and positioning system are read;

[0028] Step S2: Based on the geographic coordinates, find all the nautical charts containing the location from the electronic nautical chart dataset carried on board, and find the nautical chart with the largest scale among them;

[0029] Step S3: Calculate the geographic coordinates of the ship's current position on the nautical chart (10, 30) according to the Mercator projection forward formula;

[0030] Step S4: Extract all depth points on the electronic nautical chart to construct a nautical chart depth triangulation network. The triangle where the ship is currently located is T. Extract the map coordinates and depth values ​​of the three vertices of this triangle, which are recorded as (9.6, 28.9, 9.3), (10.9, 27.8, 9.7), and (10.3, 30.5, 8.8) respectively.

[0031] Step S5: Based on the relative positions of the ship's current position and the three vertices of the triangle (9.6, 28.9, 9.3), (10.9, 27.8, 9.7), and (10.3, 30.5, 8.8), the estimated chart depth Z of the ship's current position (10, 30) is calculated using the linear interpolation method. Chart The calculation formula is as follows, and Z is calculated. Chart The value is approximately 9.21.

[0032]

[0033] Step S6: Turn on the acoustic depth sounder equipped on board. With the ship stationary at sea, record the seawater depth values ​​and corresponding times observed by the acoustic depth sounder at 5 time points over 2 hours, with half-hour intervals, as shown in the table below:

[0034] Serial Number time Seawater depth 1 1100 12.89 2 1130 13.10 3 1200 13.28 4 1230 13.45 5 1300 13.58

[0035] Step S7: Calculate the observation time T for each observation based on the tide table values ​​on the nautical chart (or the relevant nautical book for the sea area where the ship is located). i The tidal values ​​are shown in the table below;

[0036] Serial Number time Seawater depth Tidal values 1 1100 12.89 3.57 2 1130 13.10 3.79 3 1200 13.28 3.97 4 1230 13.45 <![CDATA[4.154]]> 5 1300 13.58 4.26

[0037] Step S8: Based on the seawater depth values ​​observed continuously at 5 time points and the corresponding tidal values ​​at those times, the measured static water depth Z is determined. Survey The calculation formula is as follows, based on the calculated static water depth Z. Survey The value is approximately 9.31.

[0038]

[0039] Step S9: Estimate the water depth Z based on the chart of the ship's current position. Chart And the measured static water depth Z Survey A numerical model for instrument correction based on the mass sounding data was derived. The original depth record of the mass sounding data at this location was found to be 9.5 meters. Using the numerical model for instrument correction based on the mass sounding data, the instrument correction value ΔZ at this location can be calculated. j The accuracy was 9.39, which is 0.11 meters higher than the original mass sounding data, showing a significant improvement.

[0040]

Claims

1. A method for instrument correction based on crowdsourced bathymetry data from large-scale nautical charts, characterized in that, The method includes the following steps: Step S1: When the ship docks at a pier or anchors at a certain location at sea, turn on the ship's satellite navigation and positioning system and record the geographical coordinates of the ship's current position as (B,L); Step S2: Locate the largest scale nautical chart that includes the ship's current position; Step S3: Calculate the geographic coordinates (B,L) of the ship's current position on the nautical chart and their map coordinates (X,Y) according to the Mercator projection forward formula; Step S4: Extract all depth points on the electronic nautical chart to construct a nautical chart depth triangulation network. The triangle where the ship is currently located is T. Extract the map coordinates and depth values ​​of the three vertices of the triangle, and record them as (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3) respectively. Step S5: Based on the relative positions of the ship's current position and the three vertices of the triangle (x1, y1, z1), (x2, y2, z2), and (x3, y3, z3), calculate the estimated chart depth of the ship's current position (X, Y) using the linear triangulation method, denoted as Z. Chart ; Step S6: Turn on the acoustic depth sounder equipped on board the ship and continuously record the seawater depth values ​​and times observed by the acoustic depth sounder at n consecutive moments. Record the seawater depth values ​​observed at the n consecutive moments as (H1, H2, ..., H...). n The observation times for each observation are (T1, T2, ..., T). n ); Step S7: Calculate the observation time T for each observation based on the tide table values ​​on the nautical chart or the relevant nautical book for the sea area where the ship is located. i The tidal values, i = 1, 2, ..., n, are denoted as (Tide1, Tide2, ..., Tide...). n ); Step S8: Based on the continuously observed seawater depth values ​​(H1, H2, ..., H) at n time points n ) and the corresponding tidal values ​​(Tide1, Tide2, ..., Tide) at the time. n ), determine the measured static water depth Z. Survey ; Step S9: Estimate the water depth Z based on the chart of the ship's current position. Chart And the measured static water depth Z Survey The instrument correction numerical model for mass source bathymetry data was obtained.

2. The method for correcting instruments based on crowdsourced bathymetry data using large-scale nautical charts according to claim 1, characterized in that, In step S5, Z Chart The calculation formula is:

3. The method for instrument correction of crowdsourced bathymetry data based on large-scale nautical charts according to claim 1, characterized in that, In step S8, Z Survey The calculation formula is:

4. The method for correcting instruments based on crowdsourced bathymetry data using large-scale nautical charts according to claim 1, characterized in that, In step S9, the instrument correction numerical model for the crowdsourced bathymetry data is as follows: Where, ΔZ j This represents the instrument correction value of the mass sounding data at point j. This represents the depth value of the original mass sounding data record for a point j.

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