CN-121978721-A - Method for improving accuracy of altimetric satellite track intersection based on multiple factor constraint

Abstract

The invention relates to the technical fields of intersection such as satellite altimetry and satellite navigation, in particular to a method for improving the accuracy of an altimetric satellite track intersection based on multiple factor constraint, which comprises the following steps of data pre-screening and invalid calculation reduction; the invention introduces a quick rejection and straddling test mechanism, improves the calculation efficiency by restraining a precise cross point calculation window and other strategies, and has the capability of efficiently processing satellite data and acquiring a high-precision cross point result by calculating the large-area and high-precision satellite data provided by SWOT satellite tasks, can effectively ensure the high precision of the cross point position, and performs sea surface height calculation verification of different areas based on the algorithm, wherein the acquired sea surface height has better precision in different latitude areas.

Inventors

• ZHENG WEI
• ZHANG WENSONG
• Mao Hanchen

Assignees

• 青岛哈尔滨工业大学(威海)研究院

Dates

Publication Date

20260505

Application Date

20251215

Claims (3)

1. 1. The method for improving the accuracy of the high altitude satellite trajectory intersection based on the multiple factor constraint is characterized by comprising the following steps of: The method comprises the steps of 1, pre-screening input track lifting and track lowering data, expanding k degrees along the longitude and latitude direction according to the boundary of a research area, setting k degrees according to the average distance between observation points of selected satellites, avoiding the condition that the track data are eliminated because of discrete sampling to cause the track to pass through the area but no observation point exists in the area, and finally only retaining the track data with at least one observation point positioned in the expansion area, directly eliminating other tracks, and reducing invalid calculation; Step 2, judging whether a diagonal rectangular bounding box formed by track endpoints is coincident or not, and dividing the process into three cases, namely, rectangle coincidence and track intersection, rectangle coincidence and track disjoint, rectangle disjoint and track disjoint, wherein the rectangle coincidence and the track intersection cannot be determined, and the process comprises the steps of firstly executing a fast rejection test rapid rejection test, judging whether the diagonal rectangular bounding box formed by track endpoints is coincident or not, wherein if the bounding box is not coincident, the two tracks must not have the intersection, and the disjoint tracks can be effectively prevented from being brought into subsequent calculation; Straddling test STRADDLE TEST A straddling test judges the straddling condition of a line segment by calculating the vector cross product of two line segments, if the two line segments are straddled with each other, the two line segments are intersected, and the line segment is judged Hurdle And is also provided with Hurdle The conditions of (2) are: (1) , wherein, Finger means As the starting point The method is characterized in that the method is used as a vector of the terminal point, other vectors are the same, and the existence of the crossing point is judged through a fast rejection hurdle experiment, so that a large amount of redundant calculation can be avoided; step 3, calculating the position of the crossing point, wherein the method comprises the following steps: firstly, quickly determining longitude of a rough intersection point, wherein the orbit ground track of a satellite around the earth can be divided into two arc sections, namely an ascending orbit and a descending orbit, the ascending orbit and the descending orbit of the same satellite are assumed to be symmetrical, and when the orbit measuring point data are complete, the longitude of the rough intersection point can be obtained by utilizing the cross connection calculation of four endpoints of the two orbits according to the symmetrical characteristic; set up the end points of the lifting rail and the lowering rail respectively 、 And (3) with 、 Longitude of intersection of its lines Namely, approximate intersection longitude: (2) , wherein, 、 For the projection value of the plane coordinates of the end points, the symmetry between the ascending track and the descending track is utilized to realize the rapid calculation of the longitude of the rough intersection point, and the error is smaller than 0.5 degrees; For satellite height measurement data which is partially lost and cannot be used for rapidly calculating rough intersection longitude by using endpoints, if an intersection exists between two tracks based on symmetry between a complete ascending track and a descending track, two points with the same latitude on the two tracks 、 The average value of the longitude of (c) is close to the longitude of the intersection, or may be the approximate intersection longitude, The calculation mode of (a) is as follows: (3) , wherein, 、 Respectively is 、 Two-point longitude values; Accurate position calculation of intersection determination of approximate intersection longitude by track symmetry Thereafter, by The method is characterized in that the method comprises the steps of taking a central point, intercepting adjacent points of an ascending track and a descending track along the longitudinal direction to form a calculation window, forming constraint on the longitudinal range of a selected measuring point, and assuming that the longitudes and latitudes of the measuring points of the ascending track and the descending track in the calculation window are respectively as follows: 、 、 、 Polynomial fitting is used on the ascending track data: (4) After the fitting result of the ascending track is obtained, substituting the longitude value of the measuring point of the descending track in the calculation window Calculating corresponding lift latitude value Will be And (3) with Subtracting to obtain a group of difference values which are ordered according to the size, finding out two groups of ascending track points and descending track points with positive and negative sign changes in the group of difference values, and carrying out line segment intersection solution by utilizing the data of the two groups of points to finally obtain longitude and latitude coordinates of an accurate intersection point: (5) , wherein, 、 Longitude and latitude of the intersection point respectively, assuming that the selected track lifting point is the first And (b) Track lifting point, selected track lowering point And (b) And each.
2. 2. The method for improving the accuracy of the intersection of the high satellite trajectories based on the multiple factor constraint of claim 1, wherein after the intersection position is calculated, the sea surface altitude data at the intersection is obtained by interpolating the measurement point data near the intersection position by using an inverse distance weighting method: (7) , wherein, 、 Representing the sea level at a known point, Is the first Spherical distance between the point and the point to be calculated.
3. 3. The method for improving the accuracy of the intersection of the high satellite trajectory based on the multiple factor constraint according to claim 2, wherein in order to avoid the influence of the distant points on the sea surface altitude value at the intersection, the weighting coefficient is modified to obtain an exponential type inverse distance weighting method, so that the influence of the distant points is weakened, and the specific formula is as follows: (8) , wherein, Is the first Weight coefficient of point, after modification , The larger the value, the faster the influence of the remote measuring point on the crossing point decays.

Description

Method for improving accuracy of altimetric satellite track intersection based on multiple factor constraint Technical Field The invention relates to the technical field of intersection of satellite altimetry, satellite navigation and the like, in particular to a method for improving accuracy of a high altitude satellite track intersection based on multiple factor constraint. Background The calculation of the average sea level is primarily dependent on satellite altimetry data. Since SEASAT and GEOSAT satellites first realized continuous observation of global ocean mesoscale sea level changes, tens of altimetric satellites have been continuously released. For sea surface altimetry research, satellite data of different types and different tasks provides an important data base for average sea surface modeling. In the sea surface height measurement field, the traditional height measurement satellite continuously optimizes the observation precision through a single Shu Lei reaching technology, for example, cryoSat improves the polar ice layer and ocean monitoring capability by utilizing a synthetic aperture radar, and the Jason series establishes a high-precision reference data set of global sea level change through long-term observation of a plurality of generations of satellites, but the satellite still has the limitations of limited space coverage and difficult resolution bottleneck breaking. In 2022, month 12, SWOT (Surface Water and Ocean Topography) satellites co-launched by NASA, france CNES in combination with CAS and UKSA, by its wide swath observation technique and interferometric synthetic aperture radar (KaRIn), improved sea level altitude measurement resolution to a completely new level. The emission of the SWOT satellite marks a new stage of wide coverage and high resolution of the marine altimetry technology from the traditional single-beam radar altimetry (such as CryoSat, jason series), breaks through the limitation of the traditional altimetry in terms of space coverage and resolution, realizes the sea surface high observation with zero clearance and kilometer resolution in the global scope, and provides key data support for constructing a sea surface high model with higher precision. Compared with single-track observation of a traditional satellite, the wide swath data provided by the SWOT satellite can remarkably improve the construction precision of an average sea surface height model. However, to fully release the SWOT satellite potential, it is critical to obtain accurate satellite trajectory intersections. The intersection point is the intersection position of the ascending arc section and the descending arc section of the satellite track, and in the orbit repetition period, sea surface height parameters measured at the intersection point of the ascending arc section and the descending arc section are completely consistent, but due to factors such as observation system errors, instrument deviation, environmental interference and the like, significant differences often occur in actual data at the intersection point, and the discrepancy value can challenge the reliability of sea level change monitoring, so that the sea level height model construction is influenced. Therefore, the research of the high-precision intersection positioning method has important significance on the modeling precision reliability of the average sea surface height. Scientists have conducted extensive research in order to improve the accuracy of the computation of intersections. In 1989, tai proposed an FI algorithm (Fixed operation) which solves the position of the crossing point by orbit fitting, but the insufficient fitting precision leads to larger deviation of the result, in 2012, zhou Xiaoguang designed 11 segmentation type segmentation fitting methods which promote the calculation precision and the application range, but require manual judgment of the optimal segmentation type, and have the defect of low automation degree, in 2017, greene proposed an RST algorithm (Rapid project AND STRADDLE TEST) based on the principle of computer graphics, but the algorithm complexity led to lower calculation efficiency, in the aspect of efficiency, the grid method divides the research area into regular grids, and regards the grid center point with both the ascending and descending points as the crossing point, which is attractive due to low calculation time consumption, in 2024, zhu finds that the method has poor precision and affects the high-precision modeling of the sea level, the altitude difference method can reduce part of calculation amount, but still faces the problem of calculation time consumption when processing large-scale data, in 2021, and the method has more remarkable limitation on the calculation time consumption of the satellite data when the number of the crossing points is greatly increased when the traditional algorithm is used, and the satellite data is greatly limited by the whole calculation time co