CN-121784741-B - Single-time along-track time-sharing multi-strabismus vector flow observation method and system based on DBF

CN121784741BCN 121784741 BCN121784741 BCN 121784741BCN-121784741-B

Abstract

The application belongs to the technical field of ocean vector flow remote sensing observation, and particularly relates to a single-pass along-orbit time-sharing multi-strabismus vector flow observation method and system based on DBF. The method comprises the steps of establishing grids in a target area, setting a multi-strabismus vision direction separation requirement and a pairing time difference threshold, calculating coverage footprints of single observation according to platform and load parameters, determining the maximum interval of repeated observation of the same vision direction to realize full coverage along a track, generating a scheduling table under the condition that the constraint of digital beam forming beam switching and stabilizing capability is met, enabling each grid unit to obtain effective observation of at least two vision directions and to be capable of being solved, and then obtaining vision direction speed and solving vector flow velocity according to scheduling. The method and the device pre-arrange coverage continuity and grid resolvable constraint to an observation scheduling stage, solve the problems that the existing along-track interference observation is discontinuous in coverage, grid is lack of measurement, vector flows are difficult to acquire by single view direction, and the like, and improve the integrity, stability and engineering application value of vector flow acquisition.

Inventors

XU YONGSHENG
GUO PING

Assignees

中国科学院海洋研究所

Dates

Publication Date: 20260512
Application Date: 20260305

Claims (8)

1. The single-along-track time-sharing multi-strabismus vector flow observation method based on DBF is characterized by comprising the following steps of: S1, establishing a unified geographic grid in a target area, wherein the unified geographic grid has a step length along the track direction ; S2, setting two different strabismus vision directions for vector calculation, and setting a vision direction pairing time difference threshold, wherein the two different strabismus vision directions are respectively marked as a main vision direction A and a main vision direction B; S3, calculating ground effective footprints of different view directions in a single observation time window burst based on the platform and the load parameters, and determining the upper limit of the same view direction repetition interval according to the full coverage constraint of the same view direction along the rail by combining the ground effective footprints and the grid step length; The full coverage constraint of the same-view along-rail is that for grid cells adjacent along the rail direction, at least one effective footprint of the view X is overlapped with the effective footprint, namely the distance of the platform along-rail advance between two observations in the same view does not exceed the length of the single effective footprint, and an effective overlapping margin can be reserved: ; Wherein, the For the speed of the platform, In order to have an effective overlap margin, , The effective along-track footprint length of single burst in the view direction X is jointly determined by a platform speed, an observation time window duration, an azimuth beam opening angle, a squint geometric relation and an imaging processing effective threshold, wherein the observation time window duration and the platform speed are used for determining a coverage length caused by along-track motion, the beam opening angle and the squint geometric relation are used for determining an effective irradiation area range, and the imaging processing effective threshold is used for eliminating a low signal-to-noise ratio or a low coherence area so as to obtain an effective footprint; S4, taking a single observation time window burst as a minimum scheduling unit, and assigning strabismus directions for each single observation time window burst along a single observation time window burst time sequence on the premise of meeting the constraint of the switching capability of the digital beam forming DBF to generate an observation schedule, wherein the observation schedule at least comprises a main view direction A and a main view direction B which are alternately distributed on a time sequence according to a preset rule; The digital beam forming DBF loads and switches complex weights to form a strabismus view direction by loading array element level or subarray level channel echoes of an array antenna and completes view direction switching between adjacent bursts, and the digital beam forming DBF switching capacity constraint comprises the following steps: (a) The time constraint of the video switching and the stabilization is that the starting time interval of the window burst of the single observation of two adjacent different video directions is recorded as The time for the DBF switching and the pointing stabilization of the digital wave beam forming is not less than , ; (B) Steering angular velocity constraint, namely the view angle of two adjacent single observation time windows burst meets the following conditions: ; Wherein, the The azimuth view angle assigned to the kth single observation window burst in the time series, The minimum time to load and point to stabilize for the DBF weights, Is the maximum steering angular velocity; s5, sequentially controlling the digital beam forming DBF to form corresponding strabismus directions according to each single observation time window burst according to an observation schedule, keeping the vision directions unchanged in each single observation time window burst, and obtaining the vision direction and the vision direction speed through the double-channel along-track interference ATI in each observation time window; and S6, converging the sight line velocity into a unified geographic grid, and resolving the grid vector flow velocity.
2. The DBF-based single-track time-sharing multi-squint vector flow observation method according to claim 1, wherein in step S1, a grid cell is defined to obtain a view direction observation, wherein the view direction corresponds to a coverage intersection of a ground effective footprint of a single observation time window and the grid cell, the same grid cell allows coverage intersections of the ground effective footprint of a plurality of observation time windows with different time, respectively, and the ground effective footprint is required to meet an available coverage area of an imaging processing effective threshold.
3. The single-along-track time-sharing multi-squint vector flow observation method based on DBF according to claim 1, wherein in step S2, the main view direction A and the main view direction B are respectively located at boundary view directions at two ends of a preset view angle range in the azimuth view angle dimension, and the view angle separation constraint is satisfied: ; Wherein, the 、 The azimuth view angles of the main view direction A and the main view direction B are respectively, The method is used for guaranteeing the geometric stability of vector calculation for a preset threshold.
4. The DBF-based single-track-wise time-sharing multi-squint vector flow observation method according to claim 1, wherein in step S2 and step S4, the view direction pairing time difference threshold is And for any grid cell Covering the grid cells The single observation time window burst starting time set of all main view direction A observations is as follows Covering the grid cells The burst start time set of all main view direction B observations is And selecting a pair minimizing the absolute value of the time difference from the two combinations, and meeting the following conditions: ; Wherein min is a minimum function and a pair of observations allow burst from two single observations that are not adjacent in time.
5. The DBF-based single-track time-sharing multi-squint vector flow observation method according to claim 1, wherein in step S3, the single-track time window burst specifically refers to a discrete imaging window where a load irradiates and receives with respect to the ground within a preset start-stop time.
6. The DBF-based single-along-track time-sharing multi-squint vector flow observation method according to claim 1, wherein in step S3, the same-view repetition interval is defined as a time interval in which two occurrences of the same view X correspond to a single-view window burst start time X is A or B, and the same-view repeat interval satisfies: ; Wherein the method comprises the steps of For the starting time interval of the kth adjacent single observation window burst between occurrences of two co-views X, Is the number of observation windows between occurrences of two co-views X.
7. The DBF-based single-pass on-orbit time-sharing multi-squint vector flow observation method according to claim 1, wherein in step S4, insertion of one or more intermediate squint directions is supported on the premise that the observation schedule contains a main view direction a and a main view direction B and satisfies grid non-null and pairing time difference constraints Obtaining three or more line-of-sight velocity observations of different view directions from at least a portion of the grid cells to form a set of redundant observations and for weighted least squares solution or quality assessment, the intermediate oblique view direction The corresponding single observation time window burst allows the single observation time window burst corresponding to the main view direction A, B to be alternately distributed on the time sequence, and Corresponding azimuth view angle The method meets the following conditions: 。
8. a DBF-based single-pass, on-orbit, time-sharing, multi-strabismus vector flow observation scheduling system implementing the method of any one of claims 1-7, comprising: Grid and threshold setting module for establishing uniform geographic grid and setting And (3) with ; The upper limit calculation module of the repetition interval of the footprint and the same view direction is used for calculating the effective footprint on the ground and determining the upper limit of the repetition interval of the same view direction; The observation schedule generation module is used for generating an observation schedule meeting grid non-empty constraint, pairing time difference constraint and DBF switching capability constraint; The DBF control and data acquisition module comprises an array antenna, a multi-channel receiving link corresponding to each array element channel or subarray channel of the array antenna and a processing unit for executing digital beam forming DBF, and is used for loading the multi-channel echo data according to an observation schedule table, switching DBF weights to form corresponding strabismus vision directions, keeping the vision directions in each observation time window unchanged, and outputting two-channel cis-rail interference data for ATI processing; And the ATI speed measurement and gridding vector calculation module is used for carrying out ATI processing on the two-channel along-track interference data to obtain the sight line speed of each sight direction, converging the sight line speed into a uniform geographic grid, and calculating and outputting gridding vector flow velocity.

Description

Single-time along-track time-sharing multi-strabismus vector flow observation method and system based on DBF Technical Field The invention belongs to the technical field of ocean vector flow remote sensing observation, and particularly relates to a single-track-following time-sharing multi-strabismus vector flow observation method and system based on DBF. Background The ocean surface vector flow field information has important significance in the application of ocean power process research, pollutant drift prediction, offshore engineering, shipping safety and the like. The synthetic aperture radar has all-day, all-weather and large-range observation capability, wherein the forward-orbit interference synthetic aperture radar can acquire the line-of-sight velocity component of a water body scatterer on a shorter time scale, and an important technical approach is provided for ocean surface flow velocity monitoring. Because a single observation view direction can only obtain a sight line velocity component in one direction, in order to obtain a two-dimensional vector flow field, the prior art generally adopts a multi-squint observation mode, namely, the same area is observed under different squint directions, and then vector flow calculation is realized through equation combination. With the development of Digital Beam Forming (DBF) and other technologies, multi-view observation data can be obtained without adding parallel beam links by using a time division multi-squint mode of switching beam directions in different observation time windows by using a load. However, the existing multi-strabismus along-track interference flow measurement method still has more prominent defects on the engineering level, and is mainly characterized in that: (1) Covering discontinuous and along-track holes, namely, because a discrete time window (such as a sectionally irradiated observation time window) is adopted for observation and is switched between different viewing directions, gaps are easy to appear in the along-track direction of the ground coverage footprint, so that partial grid cells of a target area are not detected, and continuous grid data are difficult to form; (2) The single-view grid problem is that even if the whole target area is covered, partial grid units can still obtain radial observation of only a single view direction, the minimum observation condition of vector flow calculation cannot be met, and the minimum observation condition can only be supplemented by interpolation or extrapolation, so that additional errors and uncertainty are introduced; (3) The problem of uncontrollable pairing is that the observation time intervals of the same grid unit from different view directions lack uniform constraint, and the inconsistency of the observation time sequences can reduce the stability of vector calculation and influence the consistency of data; (4) The practical load wave beam switching and stabilizing capability, steering speed and the like can limit the switching frequency and the angle change amplitude between different view directions, if the multi-squint sequence is designed only from the inversion angle, the scheduling scheme can not be executed or the pairing requirement can not be met while the coverage is ensured; (5) The scheduling method facing to 'grid data' is lacking, the prior art focuses more on 'whether vector flow can be measured' and 'no holes are formed in grids, each grid can be solved, scheduling can be realized' is not used as a hard constraint of an observation stage for carrying out unified planning, and therefore available grid vector flow rate is difficult to directly output. The adverse results brought by the problems comprise that the target area vector flow velocity is subjected to space coverage missing measurement and fracture, partial grids are insoluble or unstable in resolving, errors and subjectivity are increased for interpolation repair of missing measurement and single-view grids in post-treatment, and engineering application reliability and data consistency are reduced. In summary, the existing multi-squint ATI-SAR vector flow measurement method still has the defects, and especially how to develop the observation time window boundary and the DBF scheduling design for the meshed vector flow acquisition on the premise of ensuring the space coverage continuity and high resolution is still one of the key technical problems to be solved. Disclosure of Invention The invention aims to provide a single-track-following time-sharing multi-squint vector flow observation method and system based on DBF, and the method realizes continuous coverage of a target area and paired multi-view observation of each grid unit by calculating and scheduling constraint design of single-observation coverage footprint on the premise of not increasing parallel beam links, and combines the project realizability of beam switching, stabilizing capability and the like of digital beam forming, thereby ove