A method and device for determining high-precision positioning foot points using satellite laser altimetry

Abstract

The present invention relates to a method and device for determining a high-precision positioning footpoint using satellite laser altimeter, and belongs to the technical field of satellite surveying and mapping. The method comprises acquiring discrete full waveform data of each laser point sent by a satellite laser altimeter, establishing a satellite laser altimeter footpoint positioning elevation error comprehensive model; performing regional segmentation on the fitting results of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point; screening the laser points according to parameters such as the original waveform signal-to-noise ratio and the waveform fitting residual to obtain a target laser point; inputting the fitting results of the discrete full waveform data of the target laser point into the satellite laser altimeter footpoint positioning elevation error comprehensive model to obtain an elevation error; judging and grading the target laser point according to the elevation error to obtain a high-precision positioning footpoint; thereby, the laser points can be screened and graded without requiring precise terrain parameters within a Gaofen-7 laser footprint, and the high-precision positioning footpoint can be extracted.

Description

Technical Field

[0001] The present invention relates to the field of satellite surveying and mapping technology, and in particular to a method and device for determining high-precision positioning foot points using satellite laser altimetry. Background Art

[0002] Satellite laser altimetry, as an active remote sensing technology, provides a new means of satellite remote sensing observation. By measuring the round-trip time between the laser beam emitted by the laser and the Earth, combined with information such as the satellite platform's orbital position and attitude, it is possible to calculate target surface elevation information with decimeter or even centimeter-level accuracy. This has been applied in observations of the Earth, Moon, Mars, and other planets. After emitting laser light, a full-waveform laser altimeter receives the complete backscattered waveform from the target surface, providing not only richer surface elevation profile information but also enabling quantitative analysis of the target surface's geometric and physical properties. Due to factors such as satellite laser ranging errors, satellite laser pointing errors, satellite attitude measurement errors, satellite orbit positioning errors, and topography within the laser footprint, not all laser altimeter points can meet high elevation accuracy requirements. Therefore, extracting high-precision satellite laser altimeter point data from satellite laser altimeter products is crucial for developing applications based on high-precision satellite laser altimeter points, such as using them as control points for satellite stereo mapping.

[0003] The existing technology extracts high-precision laser points based on label parameters in foreign laser altimetry products and terrain parameters calculated from publicly available global terrain data. The threshold for selecting labels is set through human experience or machine learning. However, since many of the label parameter algorithm details in foreign laser altimetry products (such as ICESat / GLAS and ICESat-2 / ATLAS) have not been made public, and the spatial scale of publicly available global terrain data is larger than the GF-7 laser footprint, existing high-precision laser altimetry point extraction methods are difficult to apply to the extraction of high-precision laser altimetry points using domestic full-waveform satellite laser altimetry.

[0004] Therefore, it is urgent to propose a method and device for determining high-precision positioning footpoints of satellite laser altimetry to solve the technical problem that the high-precision laser altimetry point extraction method in the existing technology is difficult to apply to the extraction of high-precision laser altimetry points of domestic full-waveform satellite laser altimetry because the spatial scale of global terrain data is larger than the size of the GF-7 laser footprint. Summary of the Invention

[0005] In view of this, it is necessary to provide a method and device for determining high-precision positioning footpoints of satellite laser altimetry, so as to solve the technical problem that the high-precision laser altimetry point extraction method in the existing technology is difficult to apply to the extraction of high-precision laser altimetry points of domestic full-waveform satellite laser altimetry because the spatial scale of global terrain data is larger than the size of the GF-7 laser footprint.

[0006] In order to solve the above problems, the present invention provides a method for determining a high-precision positioning footpoint by satellite laser altimetry, comprising:

[0007] Obtain the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of elevation error of satellite laser altimeter footpoint positioning;

[0008] Performing regional segmentation on the fitting result of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point;

[0009] Screening laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain a target laser point;

[0010] Inputting the fitting result of the discrete full waveform data of the target laser point into the satellite laser altimetry footpoint positioning elevation error comprehensive model to obtain the elevation error;

[0011] The target laser point is judged and graded according to the elevation error to obtain a high-precision positioning foot point.

[0012] In a possible implementation, performing regional segmentation on the fitting result of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point includes:

[0013] Calculating the discrete full waveform data to obtain the original waveform signal-to-noise ratio;

[0014] Performing regional segmentation on the fitting result of the discrete full waveform data according to a preset regional segmentation interval to obtain a waveform front end region, a waveform effective signal region, and a waveform back end region;

[0015] The fitting residuals of the front end region of the waveform, the effective signal region of the waveform and the back end region of the waveform are calculated respectively to obtain corresponding waveform fitting residuals.

[0016] In a possible implementation, respectively calculating the fitting residuals of the waveform front end region, the waveform valid signal region, and the waveform back end region to obtain corresponding waveform fitting residuals includes:

[0017] Determining the number of sampling points, duration, and sampling frequency based on the discrete full waveform data;

[0018] The sampling points in the front region of the waveform, the effective signal region of the waveform and the back region of the waveform are respectively fitted with residual calculations according to the number of sampling points, the duration and the sampling frequency to obtain corresponding waveform fitting residuals.

[0019] In one possible implementation, judging and grading the target laser point according to the elevation error to obtain a high-precision positioning foot point includes:

[0020] The target laser point is judged according to the elevation error to obtain a retained laser point;

[0021] performing grading processing on the retained laser points to obtain laser point grades;

[0022] According to the laser point level, the high-precision positioning foot point is determined.

[0023] In a possible implementation, screening the laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain the target laser point includes:

[0024] Setting a signal-to-noise ratio threshold of the original waveform signal-to-noise ratio and region thresholds corresponding to the waveform front region, the waveform valid signal region, and the waveform back region;

[0025] Comparing the original waveform signal-to-noise ratio with the signal-to-noise ratio threshold, and comparing the waveform front-end region, the waveform valid signal region, and the waveform back-end region with the corresponding region thresholds, respectively, to obtain comparison results;

[0026] When the comparison result is that the signal-to-noise ratio of the original waveform is not less than the signal-to-noise ratio threshold, and the waveform fitting residuals of the waveform front end area, the waveform valid signal area, and the waveform back end area are all not less than the corresponding area thresholds, the current laser point is determined to be the target laser point.

[0027] In a possible implementation, the method for determining the target laser point further includes:

[0028] Determining the classification type of the location of the current laser point according to the global surface coverage type, and determining whether the current laser point is a non-ground point according to the global digital elevation model;

[0029] When the current laser point is not a non-ground point and the classification type is flat ground, calculating the elevation difference between the elevation of the current laser point and the elevation in the global digital elevation model, and when the elevation difference is not greater than a preset difference threshold, determining that the current laser point is a target laser point;

[0030] When the classification type is not other types, the current laser point is determined to be a target laser point; the other types include forest type, fruit forest type and water body type.

[0031] In a possible implementation, judging the target laser point according to the elevation error to obtain a retained laser point includes:

[0032] Determining whether the elevation error is less than or equal to a preset error threshold;

[0033] If so, the retained laser point is obtained.

[0034] In a possible implementation, the grading of the retained laser points to obtain laser point grades includes:

[0035] Set the elevation accuracy index level;

[0036] The elevation error is compared with a threshold interval corresponding to each elevation accuracy index level to determine the laser point level of the retained laser point.

[0037] In one possible implementation, the waveform fitting residual is calculated as follows:

[0038]

[0039] Where, is the waveform fitting residual of each part; is the representation of the echo waveform after filtering in the fitting result; ; is the number of sampling points.

[0040] On the other hand, the present invention also provides a device for determining a foot point by using satellite laser altimetry for high-precision positioning, comprising:

[0041] The data acquisition module is used to obtain the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of the elevation error of the satellite laser altimeter footpoint positioning;

[0042] A waveform fitting module is used to perform regional segmentation on the fitting results of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point;

[0043] A laser point screening module is used to screen the laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain a target laser point;

[0044] An error calculation module is used to input the fitting result of the discrete full waveform data of the target laser point into the satellite laser altimetry footpoint positioning elevation error comprehensive model to obtain the elevation error;

[0045] The high-precision foot point determination module is used to judge and classify the target laser point according to the elevation error to obtain a high-precision positioning foot point.

[0046] The beneficial effects of the present invention are as follows: discrete full waveform data of each laser point sent by a satellite laser altimeter is obtained, and a comprehensive model of elevation error of a satellite laser altimeter footpoint is established; fitting results of the discrete full waveform data are regionally segmented to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point; laser points are screened according to parameters such as the original waveform signal-to-noise ratio and the waveform fitting residual to obtain a target laser point; fitting results of the discrete full waveform data of the target laser point are input into the comprehensive model of elevation error of a satellite laser altimeter footpoint to obtain an elevation error; the target laser point is judged and graded according to the elevation error to obtain a high-precision positioning footpoint; thereby, the laser points can be screened and graded without requiring precise terrain parameters in the Gaofen-7 laser footprint, and a high-precision positioning footpoint can be extracted. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic flow chart of an embodiment of a method for determining a foot point using high-precision satellite laser altimetry provided by the present invention;

[0048] Figure 2 For the present invention Figure 1 A schematic flow chart of an embodiment of step S102;

[0049] Figure 3 A schematic diagram showing an embodiment of the present invention showing a filtered waveform and its Gaussian fitting result;

[0050] Figure 4 For the present invention Figure 1 A schematic flow chart of an embodiment of step S105;

[0051] Figure 5 A schematic structural diagram of an embodiment of a device for determining a foot point using high-precision satellite laser altimetry provided by the present invention;

[0052] Figure 6 This is a schematic structural diagram of an embodiment of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0053] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0054] like Figure 1 As shown, a specific embodiment of the present invention discloses a method for determining a high-precision positioning footpoint using satellite laser altimetry, comprising:

[0055] S101, obtaining discrete full waveform data of each laser point sent by the satellite laser altimeter, and establishing a comprehensive model of elevation error of the satellite laser altimeter footpoint positioning;

[0056] S102, performing regional segmentation on the fitting results of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point;

[0057] S103, screening the laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain the target laser point;

[0058] S104, inputting the fitting result of the discrete full waveform data of the target laser point into the satellite laser altimetry footpoint positioning elevation error comprehensive model to obtain the elevation error;

[0059] S105: judging and grading the target laser points according to the elevation error to obtain high-precision positioning foot points.

[0060] It should be understood that: the platform measurement data can be obtained through satellite sensors, and then the sensor data of each sensor can be obtained. For example, the satellite attitude data is measured by the on-board attitude determination sensor, and the orbital positioning sensor measures the orbital position of the satellite platform. After being transmitted to the satellite, the precise attitude and precise orbit data can be output after precise attitude determination and precise orbit determination processing. The specific satellite sensors and the acquired sensor data can be set according to the actual situation, and the embodiments of the present invention are not limited here. A satellite laser ranging error model and a satellite laser altimeter footpoint positioning elevation error comprehensive model can be established. The laser ranging error value can be calculated by the satellite laser ranging error model, and then the error values ​​and sensor data of all errors can be calculated by the satellite laser altimeter footpoint positioning elevation error comprehensive model, and the elevation error of the laser point can be output. However, due to the influence of the rapid growth and change of vegetation over time, the satellite laser altimeter footpoint positioning elevation error comprehensive model has a large difference in the analysis results of the satellite laser altimeter point elevation error model for some satellite laser altimeter points that fall into the forest area and the verification results of the airborne point cloud collected at different times. In addition, there may be echo component signals of real objects in the front end area of ​​the satellite laser altimeter echo waveform. However, due to the influence of the rapid growth and change of vegetation over time, the satellite laser altimeter footpoint positioning elevation error comprehensive model has a large difference in the analysis results of the satellite laser altimeter point elevation error model for some satellite laser altimeter points that fall into the forest area and the verification results of the airborne point cloud collected at different times. In addition, the front end area of ​​the satellite laser altimeter echo waveform may have an echo component signal of real objects. However, due to the influence of the rapid growth and change of vegetation over time, the satellite laser altimeter point positioning elevation error comprehensive model has a large difference in the analysis results of the satellite laser altimeter point elevation error model for some satellite laser altimeter points that fall into the forest area and the verification results of the airborne point cloud collected at different times. In addition, the front end area of ​​the satellite laser altimeter echo waveform may have an echo component signal of real Because the echo signal is weak, the echo waveform decomposition fails to decompose the corresponding Gaussian component, which may lead to erroneous results in the error model analysis of the laser footpoint positioning elevation. This results in a significant discrepancy between the satellite laser altimetry footpoint positioning elevation error comprehensive model analysis results and the laser footpoint airborne point cloud error verification results. It can be seen that accurately extracting high-precision laser altimeter points based solely on the satellite laser altimeter positioning elevation error comprehensive model will be difficult. However, in the second issue mentioned above, the echo signal of the ground object that has not been decomposed into the corresponding echo decomposition component will usually cause the leading edge of the satellite-borne altimeter full waveform to have small fluctuations. This information will provide a reference for solving this problem. At the same time, considering that laser altimeter points falling in areas such as forest vegetation and water bodies are not suitable for use as object space in stereo mapping control information.

[0061] In a specific embodiment of the present invention, the laser emitted by the satellite laser altimeter undergoes one Fresnel diffraction, enters the earth's surface, is reflected by the target, undergoes another Fresnel diffraction, and finally reaches the telescope field of view and is received. After processes such as signal gain, photoelectric conversion, and sampling, digital discrete full waveform data is obtained. The discrete full waveform data may include the original laser altimeter echo waveform and the fitting result of the laser altimeter echo waveform. A comprehensive model of satellite laser altimeter footpoint positioning elevation error can also be established. The fitting results of the discrete full waveform data of each laser point can be regionally segmented to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point. Each laser point can also be screened according to parameters such as the original waveform signal-to-noise ratio and waveform fitting residual to obtain the target laser point. Then, the fitting results of the discrete full waveform data of the target laser point can be input into the comprehensive model of satellite laser altimeter footpoint positioning elevation error to obtain the elevation error of the target laser point. Specifically, the laser ranging error value can be calculated through the discrete full waveform data, and then other error values ​​and the data of each sensor when the laser is emitted, for example, other error values ​​include the pointing error value in the laser optical axis, the satellite attitude measurement error value and the satellite positioning error value. The sensor data includes the three-axis angle between the laser optical axis and the laser measurement platform coordinate system, the satellite attitude angle, the satellite orbit position and the ranging distance, etc. By calculating these data through the comprehensive model of satellite laser altimeter footpoint positioning elevation error, the elevation error of the target laser point can be obtained. Then, the laser point can be judged and graded by the elevation error, and a high-precision positioning footpoint can be obtained.

[0062] Compared with the prior art, the present embodiment provides a method for obtaining discrete full waveform data of each laser point sent by a satellite laser altimeter, establishing a comprehensive model for satellite laser altimeter footpoint positioning elevation errors; performing regional segmentation on the fitting results of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point; screening the laser points according to parameters such as the original waveform signal-to-noise ratio and the waveform fitting residual to obtain a target laser point; inputting the fitting results of the discrete full waveform data of the target laser point into the comprehensive model for satellite laser altimeter footpoint positioning elevation errors to obtain an elevation error; judging and grading the target laser point according to the elevation error to obtain a high-precision positioning footpoint; thereby, the laser points can be screened and graded without requiring precise terrain parameters within the GF-7 laser footprint, and high-precision positioning footpoints can be extracted.

[0063] In some embodiments of the present invention, Figure 2 As shown, step S102 includes:

[0064] S201, calculating the discrete full waveform data to obtain the original waveform signal-to-noise ratio;

[0065] S202, performing region segmentation on the discrete full waveform data according to a preset region segmentation interval to obtain a waveform front end region, a waveform valid signal region, and a waveform back end region;

[0066] S203 , respectively calculating the fitting residuals of the waveform front end region, the waveform effective signal region, and the waveform back end region to obtain corresponding waveform fitting residuals.

[0067] In a specific embodiment of the present invention, there may be echo component signals of real ground objects in the front or back end area of ​​the satellite laser altimetry echo waveform. However, due to the weak echo signal, the echo waveform decomposition fails to decompose the corresponding Gaussian component, which may lead to errors in the error model analysis results of the laser foot point positioning elevation. In order to effectively suppress such errors, it is necessary to analyze the waveform quality and waveform fitting accuracy, and to filter out the laser points corresponding to such waveforms by setting a certain threshold. The embodiment of the present invention can calculate the original waveform signal-to-noise ratio. Specifically, the discrete full waveform data can be calculated to obtain the original waveform signal-to-noise ratio, which is calculated as shown in formula (1):

[0068] (1)

[0069] Where, is the maximum amplitude of the original echo waveform, is the mean value of the background noise of the original waveform, is the noise standard deviation.

[0070] Then the fitting results of discrete full waveform data can be segmented into regions. Specifically, the regional segmentation rules can be set, that is, the regional segmentation interval. ① The normal distribution of The law, the echo waveform is located The waveform signal of can be considered as the non-effective signal area, and the waveform data in this area is the front end of the waveform; ② The waveform of the echo waveform is located at The waveform signal of the echo waveform can be considered as the effective signal area, and the waveform data in this area is the effective signal part of the waveform; ③ The waveform of the echo waveform is located at The waveform signal of can be considered as a non-valid signal area, and the waveform data in this area is the back end of the waveform. and Respectively The temporal center of gravity of the Gaussian components ( ) and RMS pulse width. The discrete full waveform data is then segmented using a regional segmentation rule to identify the waveform front-end region, the waveform valid signal region, and the waveform back-end region. The waveform quality and fitting accuracy are then evaluated using the original waveform signal-to-noise ratio and the waveform fitting residual.

[0071] In some embodiments of the present invention, step S203 includes:

[0072] Determine the number of sampling points, duration and sampling frequency based on the discrete full waveform data;

[0073] According to the number of sampling points, duration and sampling frequency, the fitting residuals of the sampling points in the front end area of ​​the waveform, the effective signal area of ​​the waveform and the back end area of ​​the waveform are calculated respectively to obtain the corresponding waveform fitting residuals.

[0074] In a specific embodiment of the present invention, the fitting results of the discrete full waveform data can be analyzed and processed to determine the number of sampling points, duration, and sampling frequency. After obtaining the region segmentation results, the sampling points of each waveform region can be determined according to the range of the waveform front region, the waveform effective signal region, and the waveform back region. Therefore, the fitting residuals of the sampling points in the waveform front region, the waveform effective signal region, and the waveform back region can be calculated according to the number of sampling points, duration, and sampling frequency, respectively, to obtain the corresponding waveform fitting residuals. The fitting results of the discrete full waveform data can be expressed as shown in formula (2):

[0075] (2)

[0076] Where, 、 and Respectively The amplitude and time center of gravity of the Gaussian components ( ) and RMS pulse width;

[0077] like Figure 3 As shown, Figure 3 The figure shows the filtered waveform and its Gaussian fitting results. The horizontal axis is time (Time), the vertical axis is voltage (Voltage), the red waveform is the echo waveform signal of the discrete full waveform data, and the blue waveform is the fitting result of the echo waveform Gaussian of the discrete full waveform data. The front part is the fitting result of the front end of the waveform, the middle part is the fitting result of the effective signal of the waveform, and the back part is the fitting result of the back end of the waveform. The residual calculation of the fitting result of each waveform area can then be performed to obtain the waveform fitting residual of each waveform area. For example, the laser altimeter echo waveform of the Gaofen-7 satellite has a duration of 400ns, a sampling frequency of 2GHz, and a total of 800 sampling points. If it is assumed that the front end of the waveform, the effective signal part, and the back end of the waveform correspond to the sampling point range of 、[ ]and[ ], the echo waveform after filtering is expressed as , then the waveform fitting residuals of each part are calculated as follows:

[0078]

[0079] Where, is the waveform fitting residual of each part; is the representation of the echo waveform after filtering in the fitting result; ; is the number of sampling points; , .

[0080] In some embodiments of the present invention, step S102 includes:

[0081] Set the signal-to-noise ratio threshold of the original waveform and the corresponding regional thresholds for the waveform front area, waveform effective signal area, and waveform back area;

[0082] Comparing the original waveform signal-to-noise ratio with the signal-to-noise ratio threshold, and comparing the waveform front-end area, the waveform effective signal area, and the waveform back-end area with the corresponding area thresholds, respectively, to obtain comparison results;

[0083] When the comparison result shows that the original waveform signal-to-noise ratio is not less than the signal-to-noise ratio threshold, and the waveform fitting residuals of the waveform front end area, the waveform effective signal area, and the waveform back end area are not less than the corresponding area thresholds, the current laser point is determined to be the target laser point.

[0084] In a specific embodiment of the present invention, a signal-to-noise ratio threshold of the original waveform signal-to-noise ratio and regional thresholds corresponding to the waveform front end area, the waveform effective signal area, and the waveform back end area can be set. Then, it can be determined whether the original waveform signal-to-noise ratio is less than the corresponding regional threshold, whether the waveform fitting residual of the waveform front end area is less than the signal-to-noise ratio threshold, whether the waveform fitting residual of the waveform effective signal area is less than the corresponding regional threshold, and whether the waveform fitting residual of the waveform back end area is less than the corresponding regional threshold. If any one of them is less than, the laser point is eliminated. If all four parameters are not less than, the laser point is retained and determined as the target laser point.

[0085] In some embodiments of the present invention, the method for determining the target laser point further includes:

[0086] Determine the classification type of the current laser point's location based on the global land cover type, and determine whether the current laser point is a non-ground point based on the global digital elevation model;

[0087] When the current laser point is not a non-ground point and the classification type is flat ground, the elevation difference between the elevation of the current laser point and the elevation in the global digital elevation model is calculated. When the elevation difference is not greater than the preset difference threshold, the current laser point is determined to be the target laser point;

[0088] When the classification type is not other types, the current laser point is determined to be the target laser point; other types include forest type, fruit forest type and water body type.

[0089] In a specific embodiment of the present invention, basic terrain reference data in the global digital elevation model and basic surface cover type reference data in the global surface cover type database are obtained, and the laser point can also be judged according to the original waveform signal-to-noise ratio and the waveform fitting residual of each waveform area to obtain the target laser point. Specifically: in ground measurement, some of the emitted laser pulse data fails to penetrate the clouds and fog, falls on the cloud layer, and is then reflected back into the field of view of the laser detector. The elevation of such laser measurement point will be significantly abnormal from the elevation of the surface point. In order to avoid interference of such laser altimetry points on the extraction of high-precision laser altimetry points, the classification type of the current laser point's location can be determined by the global land cover type FROM-GLC in the global land cover type database. The elevation of such laser points can also be judged based on the global digital elevation model AW3D30 to determine whether they are non-landing points, and such laser points of non-landing points can be removed. When the current laser point is not a non-ground point and the classification type is flat ground, that is, the elevation difference between the current laser point's elevation and the elevation of the current laser point of the global digital elevation model AW3D30 at the plane position of the point is greater than the preset difference threshold, such as 2 00m, the laser point is eliminated. If it is not greater than the preset difference threshold, the laser point can be determined to be the target laser point; considering that the laser height measurement points falling into forest vegetation, water bodies and other areas are not suitable for being used as object points in stereo mapping control information, that is, if the classification type of the location of the current laser point in the basic surface cover type reference data FROM-GLC of the global surface cover type is not other types, other types may include forest type, fruit tree forest type and water body type, that is, when the classification type is forest type, fruit tree forest type and water body type, such laser points are eliminated. If it is not these types, the laser point is determined to be the target laser point.

[0090] In some embodiments of the present invention, Figure 4 As shown, step S105 includes:

[0091] S401, judging the target laser point according to the elevation error to obtain a retained laser point;

[0092] S402, performing classification processing on the retained laser points to obtain laser point grades;

[0093] S403: Determine high-precision positioning foot points according to the laser point level.

[0094] In a specific embodiment of the present invention, the target laser point can be judged according to the elevation error to obtain a retained laser point.

[0095] It should be noted that, in order to avoid errors in the analysis of the laser height measurement foot point elevation error model due to the echo waveform decomposition problem; in some embodiments of the present invention, step S401 includes:

[0096] Determine whether the elevation error is less than or equal to a preset error threshold;

[0097] If so, the retained laser point is obtained.

[0098] In a specific embodiment of the present invention, a preset error threshold can be set. For example, if the preset error threshold is 1, laser points with elevation errors less than or equal to 1 can be retained to obtain retained laser points, otherwise the laser points will be removed.

[0099] In some embodiments of the present invention, step S402 includes:

[0100] Set the elevation accuracy index level;

[0101] The elevation error is compared with the threshold interval corresponding to each elevation accuracy index level to determine the laser point level for retaining the laser point.

[0102] In a specific embodiment of the present invention, the elevation accuracy index level can be set, and the elevation accuracy marks of the extracted high-precision Gaofen-7 satellite laser altitude points are divided into three levels (Flag=1, 2, 3), corresponding to elevation accuracies of 0.3m, 0.5m and 1m respectively; the elevation error is compared with the threshold interval corresponding to each elevation accuracy index level to determine the laser point level of the retained laser point. For example, if the elevation error is greater than 0.5m and less than or equal to 1m, the laser point is retained and the elevation accuracy index is marked as level 3 (Flag=3); if the elevation error is greater than 0.3m and less than or equal to 0.5m, the laser point is retained and the elevation accuracy index is marked as level 2 (Flag=2); if the elevation error is less than or equal to 0.3m, the laser point is retained and the elevation accuracy index is marked as level 1 (Flag=1). Each extracted and retained point has an elevation error analysis value attribute. The extracted full-waveform satellite laser altimetry high-precision points contain the following attributes: point number, elevation accuracy level, elevation error, number of echo decomposition components, laser point longitude, laser point latitude, laser point elevation, and coordinate system, as shown in Table 1:

[0103] Table 1. Examples of extraction and marking of high-precision Gaofen-7 satellite laser altimetry points

[0104]

[0105] Furthermore, the high-precision positioning foot points belonging to the high-precision corresponding level can be determined according to the laser point level.

[0106] Furthermore, the experimental area takes a certain place as an example, and the area contains a variety of landforms, such as plains, hills, mountains and canyons. The experimental data includes GF-7 laser altimeter data and high-precision airborne point cloud data; the average spatial resolution of the point cloud is 1m, and the plane and elevation accuracies are 0.5m and 0.2m respectively. The experimental data in experimental area 2 is composed of GF-7 laser altimeter data and airborne point cloud data. The experimental area contains a total of 6 tracks of laser altimeter data collected by the GF-7 satellite-borne laser altimeter system that passed through the experimental area. The embodiment of the present invention will only use laser altimeter data with a laser altimeter echo waveform decomposition component number of 1, wherein the laser altimeter data with a component number of 1 contains a total of 172 laser altimeter points. The extraction and marking results of the GF-7 laser altimeter data in the state area based on the GF-7 high-precision laser altimeter point extraction and marking method established in this article are shown in Table 2:

[0107] Table 2. Results of high-precision laser height measurement point extraction and marking

[0108]

[0109] Based on the high-precision airborne point cloud data of the experimental area (considered to be the true value of the surface elevation information), the accuracy of the laser altimetry points with different marks in the GF-7 high-precision laser altimetry point extraction results in Table 2 was verified to evaluate the effectiveness and reliability of the proposed method. The verification elevation error of each laser altimetry point was statistically analyzed, as shown in Tables 3, 4, and 5 below, which are the elevation accuracy verification results of the laser altimetry points marked as 1, 2, and 3 in the GF-7 laser altimetry point extraction results in this area.

[0110] Table 3. Elevation accuracy of laser altimetry points marked as 1 in the GF-7 high-precision laser altimetry point extraction results.

[0111]

[0112] Table 4. Elevation accuracy of laser altimetry points marked as 2 in the GF-7 high-precision laser altimetry point extraction results.

[0113] Table 5. Verification of the elevation accuracy of the laser altimetry points marked as 3 in the GF-7 high-precision laser altimetry point extraction results.

[0114]

[0115] Considering that the plane accuracy of the high-precision airborne point cloud in North Rhine-Westphalia, Germany used for accuracy verification is 0.5m and the elevation accuracy is 0.2m, therefore, according to Tables 3, 4 and 5 above, it can be considered that the elevation accuracy (absolute accuracy) of the laser height measurement point marked as 1 extracted based on the GF-7 high-precision laser high point extraction and marking method established in this paper is reliable. ; The reliability of the elevation accuracy of the laser height measurement point marked as 2 is ;

[0116] The reliability of the elevation accuracy of the laser height measurement point marked as 3 is .

[0117] Table 6. Elevation accuracy evaluation of the GF-7 high-precision laser altimeter points extracted and marked in this area

[0118]

[0119] Table 6 uses the accuracy evaluation indicators MAE and RMSE to evaluate the error of the laser height measurement points marked as 1, 2 and 3 above.

[0120] The test area contains two tracks of laser altimeter data from the Gaofen-7 satellite-borne laser altimeter system. This embodiment of the present invention only uses laser altimeter data containing only one component in the laser altimeter echo waveform decomposition. This data, with an echo decomposition component of 1, contains a total of 268 laser altimeter points. The extraction and labeling results of the Gaofen-7 laser altimeter data for this state area, using the Gaofen-7 high-precision laser altimeter point extraction and labeling method established in this embodiment of the present invention, are shown in Table 7:

[0121] Table 7. Results of extraction and marking of high-precision laser altimetry points in this area from GF-7

[0122]

[0123] Based on the high-precision airborne point cloud data in the experimental area, the accuracy of the laser altimetry points with different marks in the GF-7 advanced precision laser altimetry point extraction results in Table 7 was verified to evaluate the effectiveness and reliability of the proposed method. The verification elevation errors of each laser altimetry point were statistically analyzed, as shown in Tables 8, 9, and 10 below, which are the elevation accuracy verification results of the laser altimetry points marked as 1, 2, and 3 in the GF-7 laser altimetry point extraction results in this area.

[0124] Table 8. Verification of the elevation accuracy of the laser altimetry points marked as 1 in the GF-7 high-precision laser altimetry point extraction results.

[0125]

[0126] Table 9. Verification of the elevation accuracy of the laser altimetry points marked as 2 in the GF-7 high-precision laser altimetry point extraction results.

[0127]

[0128] Table 10. Verification of the elevation accuracy of the laser altimetry points marked as 3 in the GF-7 high-precision laser altimetry point extraction results.

[0129]

[0130] Considering that the nominal elevation accuracy of the high-precision airborne point cloud in Colorado, USA used for accuracy verification is 0.1m, the elevation accuracy (absolute accuracy) credibility of the laser height measurement points marked as 1 (the number of laser height measurement points marked as 3 is extremely small and is not counted) extracted based on the GF-7 high-precision laser high point extraction and marking method established in this paper can be calculated as follows: ; The reliability of the elevation accuracy of the laser height measurement point marked as 2 is: If the accuracy evaluation indicators MAE and RMSE are used to evaluate the error of the laser height measurement points marked as 1, 2 and 3, the results are shown in Table 11:

[0131] Table 11. Elevation accuracy evaluation of the GF-7 high-precision laser altimeter points extracted and marked in this area

[0132]

[0133] Based on the above experiments, it can be calculated that the confidence levels of the laser points marked as Level 1, Level 2, and Level 3 extracted from single-echo component laser altimetry data using the full-waveform satellite laser altimetry high-precision laser altimetry point extraction and marking method established by the present invention are 95.1%, 93.6%, and 93.5%, respectively. Furthermore, the actual elevation errors of the laser points marked as Level 1, Level 2, and Level 3 elevation accuracy are 0.73m, 1.13m, and 1.37m, respectively, with mean errors of 0.13m, 0.21m, and 0.37m, respectively. The scheme within the present invention can accurately extract high-precision laser altimetry points from full-waveform satellite laser altimetry.

[0134] In order to better implement the satellite laser altimetry high-precision positioning footpoint determination method in the embodiment of the present invention, based on the satellite laser altimetry high-precision positioning footpoint determination method, the embodiment of the present invention also provides a satellite laser altimetry high-precision positioning footpoint determination device, such as Figure 5 As shown, the satellite laser altimetry high-precision positioning foot point determination device 500 includes:

[0135] The data acquisition module 501 is used to obtain the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of the elevation error of the satellite laser altimeter footpoint positioning;

[0136] The waveform fitting module 502 is used to perform region segmentation on the fitting results of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point;

[0137] The laser point screening module 503 is used to screen the laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain the target laser point;

[0138] The error calculation module 504 is used to input the fitting result of the discrete full waveform data of the target laser point into the satellite laser altimetry footpoint positioning elevation error comprehensive model to obtain the elevation error;

[0139] The high-precision foot point determination module 505 is used to judge and classify the target laser point according to the elevation error to obtain a high-precision positioning foot point.

[0140] The satellite laser altimetry high-precision positioning foot point determination device 500 provided in the above embodiment can implement the technical solution described in the above embodiment of the satellite laser altimetry high-precision positioning foot point determination method. The specific implementation principles of the above modules or units can refer to the corresponding contents in the above embodiment of the satellite laser altimetry high-precision positioning foot point determination method, which will not be repeated here.

[0141] like Figure 6 As shown, the present invention also provides an electronic device 600. The electronic device 600 includes a processor 601, a memory 602 and a display 603. Figure 6 Only some of the components of the electronic device 600 are shown, but it should be understood that implementation of all of the shown components is not required, and more or fewer components may be implemented instead.

[0142] In some embodiments, the memory 602 may be an internal storage unit of the electronic device 600, such as a hard disk or memory of the electronic device 600. In other embodiments, the memory 602 may also be an external storage device of the electronic device 600, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the electronic device 600.

[0143] Furthermore, the memory 602 may include both an internal storage unit of the electronic device 600 and an external storage device. The memory 602 is used to store application software installed in the electronic device 600 and various data.

[0144] In some embodiments, the processor 601 can be a central processing unit (CPU), a microprocessor, or other data processing chip, used to run the program code or process data stored in the memory 602, such as the satellite laser altimetry high-precision positioning foot point determination method in the present invention.

[0145] In some embodiments, the display 603 can be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, or an OLED (Organic Light-Emitting Diode) touchscreen. The display 603 is used to display information about the electronic device 600 and to display a visual user interface. Components 601-603 of the electronic device 600 communicate with each other via a system bus.

[0146] In some embodiments of the present invention, when the processor 601 executes the satellite laser altimetry high-precision positioning footpoint determination program in the memory 602, the following steps may be implemented:

[0147] Obtain the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of elevation error of satellite laser altimeter footpoint positioning;

[0148] Perform regional segmentation on the fitting results of discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point;

[0149] The laser points are screened according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain the target laser point;

[0150] The fitting result of the discrete full waveform data of the target laser point is input into the comprehensive model of elevation error of satellite laser altimetry footpoint positioning to obtain the elevation error;

[0151] The target laser points are judged and graded according to the elevation error to obtain high-precision positioning foot points.

[0152] It should be understood that when the processor 601 executes the satellite laser altimetry high-precision positioning foot point determination program in the memory 602, in addition to the above functions, it can also implement other functions. For details, please refer to the description of the corresponding method embodiment above.

[0153] Furthermore, the embodiments of the present invention do not specifically limit the type of electronic device 600 mentioned. The electronic device 600 may be a portable electronic device such as a mobile phone, tablet computer, personal digital assistant (PDA), wearable device, or laptop computer. Exemplary embodiments of portable electronic devices include, but are not limited to, portable electronic devices running iOS, Android, Microsoft, or other operating systems. The portable electronic devices mentioned above may also be other portable electronic devices, such as a laptop computer with a touch-sensitive surface (e.g., a touch panel). It should also be understood that in some other embodiments of the present invention, the electronic device 600 may not be a portable electronic device, but rather a desktop computer with a touch-sensitive surface (e.g., a touch panel).

[0154] Accordingly, an embodiment of the present application also provides a computer-readable storage medium, which is used to store computer-readable programs or instructions. When the program or instructions are executed by the processor, it can implement the satellite laser altimetry high-precision positioning foot point determination method steps or functions provided in the above-mentioned method embodiments.

[0155] Those skilled in the art will appreciate that all or part of the process flow of the above-described method embodiment can be implemented by instructing related hardware (such as a processor, controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a magnetic disk, an optical disk, a read-only memory, or a random access memory.

[0156] The above is a detailed introduction to the satellite laser altimetry high-precision positioning foot point determination method and device provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for technical personnel in this field, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for determining foot points using satellite laser altimetry with high precision, characterized in that: include: Obtain the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of elevation error of satellite laser altimeter footpoint positioning; Performing regional segmentation on the fitting result of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point; Screening laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain a target laser point; Inputting the fitting result of the discrete full waveform data of the target laser point into the satellite laser altimetry footpoint positioning elevation error comprehensive model to obtain the elevation error; The target laser point is judged and graded according to the elevation error to obtain a high-precision positioning foot point.

2. The method for determining foot points by satellite laser altimetry high-precision positioning according to claim 1, characterized in that: The performing of regional segmentation on the fitting result of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point includes: Calculating the discrete full waveform data to obtain the original waveform signal-to-noise ratio; Performing regional segmentation on the fitting result of the discrete full waveform data according to a preset regional segmentation interval to obtain a waveform front end region, a waveform effective signal region, and a waveform back end region; The fitting residuals of the front end region of the waveform, the effective signal region of the waveform and the back end region of the waveform are calculated respectively to obtain corresponding waveform fitting residuals.

3. The method for determining foot points by satellite laser altimetry high-precision positioning according to claim 2, characterized in that: The step of calculating the fitting residuals of the waveform front end region, the waveform valid signal region, and the waveform back end region respectively to obtain corresponding waveform fitting residuals includes: Determining the number of sampling points, duration, and sampling frequency based on the discrete full waveform data; The sampling points in the front region of the waveform, the effective signal region of the waveform and the back region of the waveform are respectively fitted with residual calculations according to the number of sampling points, the duration and the sampling frequency to obtain corresponding waveform fitting residuals.

4. The method for determining foot points by satellite laser altimetry high-precision positioning according to claim 2, characterized in that: The step of judging and grading the target laser point according to the elevation error to obtain a high-precision positioning foot point includes: The target laser point is judged according to the elevation error to obtain a retained laser point; performing grading processing on the retained laser points to obtain laser point grades; According to the laser point level, the high-precision positioning foot point is determined.

5. The method for determining foot points by satellite laser altimetry high-precision positioning according to claim 2, characterized in that: The step of screening the laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain the target laser point includes: Setting a signal-to-noise ratio threshold of the original waveform signal-to-noise ratio and region thresholds corresponding to the waveform front region, the waveform valid signal region, and the waveform back region; Comparing the original waveform signal-to-noise ratio with the signal-to-noise ratio threshold, and comparing the waveform front-end region, the waveform valid signal region, and the waveform back-end region with the corresponding region thresholds, respectively, to obtain comparison results; When the comparison result is that the signal-to-noise ratio of the original waveform is not less than the signal-to-noise ratio threshold, and the waveform fitting residuals of the waveform front end area, the waveform valid signal area, and the waveform back end area are all not less than the corresponding area thresholds, the current laser point is determined to be the target laser point.

6. The method for determining foot points by satellite laser altimetry high-precision positioning according to claim 5, characterized in that: The method for determining the target laser point also includes: Determining the classification type of the location of the current laser point according to the global surface coverage type, and determining whether the current laser point is a non-ground point according to the global digital elevation model; When the current laser point is not a non-ground point and the classification type is flat ground, calculating the elevation difference between the elevation of the current laser point and the elevation in the global digital elevation model, and when the elevation difference is not greater than a preset difference threshold, determining that the current laser point is a target laser point; When the classification type is not other types, the current laser point is determined to be a target laser point; the other types include forest type, fruit forest type and water body type.

7. The method for determining foot points by satellite laser altimetry high-precision positioning according to claim 4, characterized in that: The step of judging the target laser point according to the elevation error to obtain a retained laser point includes: Determining whether the elevation error is less than or equal to a preset error threshold; If so, the retained laser point is obtained.

8. The method for determining foot points by satellite laser altimetry high-precision positioning according to claim 4, characterized in that: The step of performing grading processing on the retained laser points to obtain laser point grades includes: Set the elevation accuracy index level; The elevation error is compared with a threshold interval corresponding to each elevation accuracy index level to determine the laser point level of the retained laser point.

9. The method for determining foot points by satellite laser altimetry high-precision positioning according to claim 1, characterized in that: The waveform fitting residual is calculated as follows: Where, is the waveform fitting residual of each part; is the representation of the echo waveform after filtering in the fitting result; ; is the number of sampling points.

10. A device for determining foot points by using satellite laser altimetry for high-precision positioning, characterized in that: include: The data acquisition module is used to obtain the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of the elevation error of the satellite laser altimeter footpoint positioning; A waveform fitting module is used to perform regional segmentation on the fitting results of the discrete full waveform data to obtain the original waveform signal-to-noise ratio and waveform fitting residual of each laser point; A laser point screening module is used to screen the laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain a target laser point; An error calculation module is used to input the fitting result of the discrete full waveform data of the target laser point into the satellite laser altimetry footpoint positioning elevation error comprehensive model to obtain the elevation error; The high-precision foot point determination module is used to judge and classify the target laser point according to the elevation error to obtain a high-precision positioning foot point.

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