Satellite laser height measurement high-precision positioning foot point determination method and device

Abstract

The invention relates to a satellite laser altimetry high-precision positioning foot point determination method and device, and belongs to the technical field of satellite surveying and mapping, the method comprises the following steps: obtaining discrete full waveform data of each laser point sent by a satellite laser altimeter, and establishing a satellite laser altimetry foot point positioning elevation error comprehensive model; performing region segmentation on the fitting result of the discrete full-waveform data to obtain an original waveform signal-to-noise ratio and a waveform fitting residual error of each laser point; screening the laser points according to parameters such as an original waveform signal-to-noise ratio and a waveform fitting residual error to obtain a target laser point; inputting a fitting result of the discrete full-waveform data of the target laser point into a satellite laser height measurement foot point 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 foot point; therefore, the laser points can be screened and graded under the condition that precise terrain parameters in the high-resolution No.7 laser footprint are not needed, and high-precision positioning foot points are 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 a high-precision positioning foot point by satellite laser altimetry. Background Art

[0002] Satellite laser altimetry, as an active remote sensing technology, provides a new satellite remote sensing observation method for human beings. By measuring the round-trip time of the laser emitted by the laser, combined with the orbital position and attitude of the satellite platform, the elevation information of the target surface with decimeter or even centimeter accuracy can be calculated. It has been applied in the observation of the earth, the moon, Mars and other planets. After emitting laser, the full-waveform laser altimeter can receive the complete backscattered waveform of the target surface, which can not only obtain richer surface profile elevation information, but also can be used to quantitatively analyze the geometric and physical properties of the target surface. Due to the influence of factors such as satellite laser ranging error, satellite laser pointing error, satellite attitude measurement error, satellite orbit positioning error and topography in the laser footprint, not all laser altimetry points can meet the high elevation accuracy requirements. How to extract high-precision satellite laser altimetry point data based on satellite laser altimetry products is crucial for the development of applications based on high-precision satellite laser altimetry points, such as using high-precision satellite laser altimetry points as satellite stereo mapping control points.

[0003] The existing technology is based on the label parameters in foreign laser altimetry products and the terrain parameters calculated from the public global terrain data. The threshold of the selected label is set through human experience or machine learning to extract high-precision laser points. However, since many label parameter algorithm details in foreign laser altimetry products (such as ICESat / GLAS and ICESat-2 / ATLAS) are not disclosed, and the spatial scale of the public global terrain data is larger than the size of the GF-7 laser footprint, the existing high-precision laser altimetry point extraction method is difficult to apply to the extraction of high-precision laser altimetry points in 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 prior art 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 foot point by high-precision positioning using satellite laser altimetry, comprising: Obtain the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of elevation error for 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; The laser points are screened 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 height measurement foot point 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.

[0007] 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: 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 the 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.

[0008] 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: Determine the number of sampling points, duration and sampling frequency according to the discrete full waveform data; 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 according to the number of sampling points, the duration and the sampling frequency to obtain corresponding waveform fitting residuals.

[0009] In a possible implementation, 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 reserved 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.

[0010] In a possible implementation, the screening of laser points according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain a target laser point includes: Setting a signal-to-noise ratio threshold of the original waveform signal-to-noise ratio and area thresholds corresponding to the waveform front end area, the waveform effective signal area, and the waveform back end area; Comparing the original waveform signal-to-noise ratio with the signal-to-noise ratio threshold, and comparing the waveform front end region, the waveform effective signal region, and the waveform rear end region with the corresponding region thresholds, respectively, to obtain a comparison result; When the comparison result is 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 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.

[0011] In a possible implementation manner, the method for determining the target laser point further includes: Determine the classification type of the location of the current laser point according to the global surface coverage type, and determine 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.

[0012] In a possible implementation, judging the target laser point according to the elevation error to obtain a reserved laser point includes: Determine whether the elevation error is less than or equal to a preset error threshold; If yes, the reserved laser point is obtained.

[0013] In a possible implementation, the grading process of 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.

[0014] In a possible implementation, the waveform fitting residual is calculated as follows:

[0015] In the formula, is the waveform fitting residual of each part; It is the representation of the echo waveform after filtering in the fitting result; ; is the number of sampling points.

[0016] On the other hand, the present invention also provides a device for determining a foot point by high-precision positioning by satellite laser altimetry, comprising: 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 elevation error of the satellite laser altimeter foot point positioning; A waveform fitting module, used for 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; A laser point screening module, used for screening 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, used for inputting the fitting result of the discrete full waveform data of the target laser point into the satellite laser height measurement foot point 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.

[0017] The beneficial effects of the present invention are as follows: obtaining discrete full waveform data of each laser point sent by a satellite laser altimeter, establishing a comprehensive model of elevation error for satellite laser altimeter footpoint positioning; performing regional segmentation on the fitting results of the discrete full waveform data, obtaining 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, obtaining the target laser points; inputting the fitting results of the discrete full waveform data of the target laser points into the comprehensive model of elevation error for satellite laser altimeter footpoint positioning, obtaining the elevation error; judging and grading the target laser points according to the elevation error, obtaining high-precision positioning footpoints; thereby screening and grading the laser points without the need for precise terrain parameters in the GF-7 laser footprint, and extracting high-precision positioning footpoints. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic flow chart of an embodiment of a method for determining a foot point by high-precision positioning using satellite laser altimetry provided by the present invention; Figure 2 For the present invention Figure 1 A schematic flow chart of an embodiment of step S102; Figure 3 A schematic diagram of an embodiment structure showing a waveform after filtering and a Gaussian fitting result thereof provided by the present invention; Figure 4 For the present invention Figure 1 A schematic flow chart of an embodiment of step S105; Figure 5 A schematic structural diagram of an embodiment of a device for determining a foot point by high-precision satellite laser altimetry provided by the present invention; Figure 6 A schematic structural diagram of an embodiment of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention are 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, but are not used to limit the scope of the present invention.

[0020] like Figure 1 As shown, a specific embodiment of the present invention discloses a method for determining a foot point by high-precision positioning using satellite laser altimetry, comprising: 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 foot point positioning; S102, 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; 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; S104, inputting the fitting result of the discrete full waveform data of the target laser point into the satellite laser height measurement foot point positioning elevation error comprehensive model to obtain the elevation error; S105, judging and grading the target laser point according to the elevation error to obtain a high-precision positioning foot point.

[0021] It should be understood that: 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 sensor, and the orbital positioning sensor measures the orbital position of the satellite platform. After being transmitted to the satellite, precise attitude and precise orbit data can be output after precise attitude and precise orbit determination processing. The specific satellite sensors and the acquired sensor data can be set according to actual conditions, 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. Then, the error values ​​and sensor data of all errors are 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 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 airborne point cloud verification results 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 Due to the weak echo signal, the echo waveform decomposition failed to decompose the corresponding Gaussian component, which may lead to the error model analysis results of the laser foot point positioning elevation, resulting in a large difference between the satellite laser altimetry foot point positioning elevation error comprehensive model analysis results and the laser foot point airborne point cloud error verification results. It can be seen that it is difficult to accurately extract high-precision laser altimetry points based only on the satellite laser altimetry foot point positioning elevation error comprehensive model. However, in the above second problem of the satellite laser altimetry foot point positioning elevation error comprehensive model, the echo signal of the ground object that has not decomposed the corresponding echo decomposition component will usually cause the front part of the satellite-borne altimetry full waveform to have small fluctuations. This information will provide a reference for solving this problem. At the same time, considering that the laser altimetry points that fall into forest vegetation, water bodies and other areas are not suitable for use as objects in stereo mapping control information.

[0022] In a specific embodiment of the present invention, the laser emitted by a satellite laser altimeter undergoes one Fresnel diffraction, is incident on the earth's surface, is reflected by a target, undergoes another Fresnel diffraction, and finally reaches the field of view of a telescope 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 elevation error for satellite laser altimeter footpoint positioning 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 the 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. These data are calculated through the comprehensive model of satellite laser altimeter footpoint positioning elevation error to obtain the elevation error of the target laser point. Then, the laser point can be judged and graded by the elevation error, and a high-precision positioning footpoint can be obtained.

[0023] 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 of elevation error for satellite laser altimeter footpoint positioning; 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 the target laser point; inputting the fitting results of the discrete full waveform data of the target laser point into the comprehensive model of elevation error for satellite laser altimeter footpoint positioning to obtain the 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 the need for precise terrain parameters in the GF-7 laser footprint to extract the high-precision positioning footpoint.

[0024] In some embodiments of the present invention, Figure 2 As shown, step S102 includes: S201, calculating the discrete full waveform data to obtain the original waveform signal-to-noise ratio; 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 effective signal region, and a waveform back end region; 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.

[0025] In a specific embodiment of the present invention, there may be echo component signals of real 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 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. Specifically, the discrete full waveform data can be calculated to obtain the original waveform signal-to-noise ratio, and the calculation is shown in formula (1): (1) In the formula, 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.

[0026] 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 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 echo waveform is located at The waveform signal of 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 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 centroid of the Gaussian components ( ) and RMS pulse width. Then, the discrete full waveform data is segmented by the regional segmentation rule, and the waveform front end area, waveform effective signal area and waveform back end area can be obtained. Then, the waveform quality and fitting accuracy are evaluated by the original waveform signal-to-noise ratio and waveform fitting residual.

[0027] In some embodiments of the present invention, step S203 includes: According to the discrete full waveform data, determine the number of sampling points, duration and sampling frequency; 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.

[0028] In a specific embodiment of the present invention, the fitting result of the discrete full waveform data can be analyzed and processed to determine the number of sampling points, duration and sampling frequency. After the region segmentation result is obtained, 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 result of the discrete full waveform data can be expressed as shown in formula (2): (2) In the formula, , and Respectively The amplitude and time center of gravity of the Gaussian components ( ) and RMS pulse width; 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 Gaussian fitting result 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. Then the residual calculation can be performed on the fitting results of each waveform area, and the waveform fitting residual of each waveform area can be obtained. For example, the laser altimetry echo waveform of the Gaofen-7 satellite contains 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 residual calculation of each part is as follows:

[0029] In the formula, is the waveform fitting residual of each part; It is the representation of the echo waveform after filtering in the fitting result; ; is the number of sampling points; , .

[0030] In some embodiments of the present invention, step S102 includes: Set the signal-to-noise ratio threshold of the original waveform signal-to-noise ratio and the area thresholds corresponding to the waveform front-end area, waveform effective signal area, and waveform back-end area; The original waveform signal-to-noise ratio is compared with the signal-to-noise ratio threshold, and the waveform front-end region, the waveform effective signal region and the waveform back-end region are respectively compared with the corresponding region thresholds to obtain a comparison result; When the comparison result is 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.

[0031] 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, waveform effective signal area, and waveform back end area can be set, and 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.

[0032] In some embodiments of the present invention, the method for determining a target laser point further includes: Determine the classification type of the location of the current laser point according to the global surface coverage type, and determine 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, 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; 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.

[0033] 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, there is a part of the emitted laser pulse data that 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 such laser altimetry points from interfering with the extraction of high-precision laser altimetry points, the classification type of the current laser point's location can be determined through 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-ground points, and such laser points of non-ground 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 the 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 includes forest type, fruit tree forest type and water body type, such laser points are eliminated. If they are not these types, the laser point is determined to be the target laser point.

[0034] In some embodiments of the present invention, Figure 4 As shown, step S105 includes: S401, judging the target laser point according to the elevation error to obtain a retained laser point; S402, performing classification processing on the retained laser points to obtain laser point grades; S403, determining high-precision positioning foot points according to the laser point level.

[0035] In a specific embodiment of the present invention, the target laser point can be judged according to the elevation error to obtain the reserved laser point.

[0036] 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: Determine whether the elevation error is less than or equal to a preset error threshold; If yes, the reserved laser point is obtained.

[0037] 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.

[0038] In some embodiments of the present invention, step S402 includes: Set the elevation accuracy index level; 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.

[0039] In a specific embodiment of the present invention, the elevation accuracy index level can be set, and the elevation accuracy mark of the extracted high-precision Gaofen-7 satellite laser altimetry point is divided into three levels (Flag=1, 2, 3), corresponding to the elevation accuracy 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), and 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: Table 1. Examples of extraction and marking of high-precision Gaofen-7 satellite laser altimetry points

[0040] Furthermore, the high-precision positioning foot points belonging to the high-precision corresponding level can be determined according to the laser point level.

[0041] Furthermore, taking a certain place as an example of the experimental area, the area contains a variety of landforms, such as plains, hills, mountains and canyons. The experimental data include 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: Table 2. Results of high-precision laser height measurement point extraction and marking

[0042] Based on the high-precision airborne point cloud data of the experimental area 1 (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 is verified, which can evaluate the effectiveness and credibility of the method in this paper, and the verification elevation error of each laser altimetry point is 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; Table 3. Elevation accuracy of laser altimetry points marked as 1 in the GF-7 high-precision laser altimetry point extraction results

[0043] Table 4. Elevation accuracy of laser altimetry points marked as 2 in the GF-7 high-precision laser altimetry point extraction results

[0044] 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

[0045] 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 ; The reliability of the elevation accuracy of the laser height measurement point marked as 3 is .

[0046] Table 6. Elevation accuracy evaluation of the GF-7 high-precision laser altimeter points extracted and marked in this area

[0047] Table 6 uses the accuracy evaluation indicators MAE and RMSE to evaluate the errors of the laser height measurement points marked as 1, 2 and 3.

[0048] The test area contains 2-track laser altimeter data of the GF-7 satellite-borne laser altimeter system. The embodiment of the present invention will only use laser altimeter data containing only one component in the laser altimeter echo waveform decomposition, wherein the laser altimeter data with 1 echo decomposition component contains a total of 268 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 the embodiment of the present invention are shown in Table 7: Table 7. Results of extraction and marking of high-precision laser altimetry points in this area

[0049] 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. The effectiveness and credibility of the method in this paper can be evaluated, and the verification elevation errors of each laser altimetry point are 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.

[0050] 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

[0051] 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

[0052] 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

[0053] Considering that the nominal accuracy of the high-precision airborne point cloud elevation in Colorado, USA used for accuracy verification is 0.1m, the credibility of the elevation accuracy (absolute accuracy) of the laser height measurement points marked as 1 (the number of laser height measurement points marked as 3 is very small, and the credibility 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: Table 11. Elevation accuracy evaluation of the GF-7 high-precision laser altimeter points extracted and marked in this area

[0054] If the above experiments are combined, it can be calculated that the reliability of the elevation accuracy of the laser points marked as level 1, level 2 and level 3 extracted by the full-waveform satellite laser altimetry high-precision laser altimetry point extraction and marking method established by the embodiment of the present invention under the single echo component laser altimetry data is 95.1%, 93.6% and 93.5% respectively. At the same time, 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 at most, and the mean errors are 0.13m, 0.21m and 0.37m. The scheme in the embodiment of the present invention can realize the accurate extraction of high-precision laser altimetry points of full-waveform satellite laser altimetry.

[0055] In order to better implement the satellite laser altimetry high-precision positioning foot point determination method in the embodiment of the present invention, based on the satellite laser altimetry high-precision positioning foot point determination method, the embodiment of the present invention also provides a satellite laser altimetry high-precision positioning foot point determination device, such as Figure 5 As shown, the satellite laser altimetry high-precision positioning foot point determination device 500 includes: The data acquisition module 501 is used to acquire the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of elevation error of the satellite laser altimeter foot point positioning; The waveform fitting module 502 is used to perform region 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; 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; 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 height measurement foot point positioning elevation error comprehensive model to obtain the elevation error; 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.

[0056] 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 satellite laser altimetry high-precision positioning foot point determination method embodiment. The specific implementation principles of the above modules or units can refer to the corresponding contents in the above satellite laser altimetry high-precision positioning foot point determination method embodiment, which will not be repeated here.

[0057] 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 components of the electronic device 600 are shown, but it should be understood that it is not required to implement all of the components shown, and more or fewer components may be implemented instead.

[0058] 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.

[0059] 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.

[0060] In some embodiments, the processor 601 can be a central processing unit (CPU), a microprocessor or other data processing chip, which is 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.

[0061] In some embodiments, the display 603 may be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, an OLED (Organic Light-Emitting Diode) touch device, etc. The display 603 is used to display information of the electronic device 600 and to display a visual user interface. The components 601-603 of the electronic device 600 communicate with each other through a system bus.

[0062] 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: Obtain the discrete full waveform data of each laser point sent by the satellite laser altimeter and establish a comprehensive model of elevation error for satellite laser altimeter footpoint positioning; 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; The laser points are screened according to the original waveform signal-to-noise ratio and the waveform fitting residual to obtain the target laser points; The fitting result of the discrete full waveform data of the target laser point is input into the comprehensive model of elevation error of the satellite laser height measurement foot point positioning to obtain the elevation error; The target laser points are judged and graded according to the elevation error to obtain high-precision positioning foot points.

[0063] 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, other functions can also be implemented. For details, please refer to the description of the corresponding method embodiment above.

[0064] Furthermore, the embodiment of the present invention does not specifically limit the type of the electronic device 600 mentioned, and the electronic device 600 may be a portable electronic device such as a mobile phone, a tablet computer, a personal digital assistant (PDA), a wearable device, a laptop computer, etc. Exemplary embodiments of portable electronic devices include but are not limited to portable electronic devices equipped with IOS, Android, Microsoft or other operating systems. The above-mentioned portable electronic devices 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 a desktop computer with a touch-sensitive surface (e.g., a touch panel).

[0065] 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 a 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.

[0066] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware (such as a processor, a controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0067] 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 idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for determining foot points by high-precision positioning using satellite laser altimetry, 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 for 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; The laser points are screened 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 height measurement foot point 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 with high precision according to claim 1, characterized in that: The step of 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: 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 the 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 with high precision according to claim 2, characterized in that: The step of calculating 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 respectively to obtain the corresponding waveform fitting residuals comprises: Determine the number of sampling points, duration and sampling frequency according to the discrete full waveform data; 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 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 with high precision 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 reserved 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 with high precision 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 points includes: Setting a signal-to-noise ratio threshold of the original waveform signal-to-noise ratio and area thresholds corresponding to the waveform front end area, the waveform effective signal area, and the waveform back end area; Comparing the original waveform signal-to-noise ratio with the signal-to-noise ratio threshold, and comparing the waveform front end region, the waveform effective signal region, and the waveform rear end region with the corresponding region thresholds, respectively, to obtain a comparison result; When the comparison result is 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 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 high-precision positioning using satellite laser altimetry according to claim 5, characterized in that: The method for determining the target laser point also includes: Determine the classification type of the location of the current laser point according to the global surface coverage type, and determine 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 with high precision according to claim 5, characterized in that: The step of judging the target laser point according to the elevation error to obtain a retained laser point includes: Determine whether the elevation error is less than or equal to a preset error threshold; If yes, the reserved laser point is obtained.

8. The method for determining foot points by satellite laser altimetry with high precision according to claim 5, 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 with high precision according to claim 1, characterized in that: The waveform fitting residual is calculated as follows: In the formula, is the waveform fitting residual of each part; It 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 and 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 elevation error of the satellite laser altimeter foot point positioning; A waveform fitting module, used for 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; A laser point screening module, used for screening 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, used for inputting the fitting result of the discrete full waveform data of the target laser point into the satellite laser height measurement foot point 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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