Aspect Angle Progression Determination Using Road Information
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Solution Overview
Problem
Current ISAR systems face challenges in accurately determining the aspect angle progression of moving vehicles, leading to distorted or blurred images due to insufficient knowledge of vehicle movement, especially when angular velocity is not constant, and the temporal separation of vehicle movement and ISAR data acquisition introduces errors.
Innovation Solution
The method involves linking radar data with road information to determine the vehicle's position and speed, using digital maps or SAR images, and calculating the aspect angle from the positions and directions of the radar sensor and vehicle, evaluating the radiometric center of gravity for motion compensation, which allows for accurate aspect angle determination without relying on reflectivity distribution in range-Doppler segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the aspect angle progression is determined from reflectivity distribution in range-Doppler segments, then the aspect angle can be estimated, but the reflectivity distribution changes greatly with aspect angle leading to estimation errors
Solution Approach 1:
The patent introduces road information (digital maps, SAR images) as an intermediary to determine vehicle position and speed independently of the problematic reflectivity distribution. This intermediary approach allows aspect angle calculation without relying on the aspect-angle-dependent reflectivity patterns, thereby eliminating the estimation errors caused by reflectivity changes.
Solution Approach 2:
The patent creates a geometric model (copy) of the vehicle's motion trajectory by linking radar distance measurements with road map information. This geometric copy allows reconstruction of the aspect angle progression without directly observing the reflectivity distribution, providing a reliable alternative to the flawed direct observation method.
2Measurement precision
If MTI, track tracking and ISAR acquisition are operated in multiplex, then aspect angle information can be determined, but this presents a particular challenge that even sophisticated radar systems can only meet in exceptional cases
Solution Approach 1:
The patent extracts the aspect angle determination task from the complex multiplexed MTI/track/ISAR system. By using road information and simple distance measurements, the aspect angle can be determined independently without requiring complex multiplexed operations, thereby reducing system complexity while maintaining accuracy.
3Ease of manufacture
If the aspect angle progression is not accurately determined, then image generation cannot be performed, but the knowledge of vehicle movement is generally not available or only available with insufficient accuracy
Solution Approach 1:
The patent uses road information (digital maps, SAR images) as an intermediary to recover vehicle movement information that would otherwise be unavailable. By combining this intermediary with simple radar distance measurements, the system can accurately determine aspect angle progression without requiring complex vehicle movement sensing, thereby enabling image generation while recovering lost information.
Data Source
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AI summary
The invention relates to a method and a device for determining the progression of the aspect angle at which the radar of the vehicle illuminates during imaging and at which the vehicle echoes are reflected back to the radar. Under the assumption that the course of a vehicle to be imaged is predetermined by an infrastructure facility to be used by said vehicle, such as a street, the course thereof is used as additional knowledge. Using the distance between the radar sensor and the vehicle, as well as the change in distance, both determined from the radar data, the position and the speed of the vehicle at each point in time of the image are determined by a link to the street information. The aspect angle is then determined from the positions of the sensor and the vehicle, as well as the direction of motion of the vehicle. The required street information can be obtained from digital maps or images (e.g., optical aerial images, SAR images). The aspect angle progression can thus advantageously be determined from the acquired ISAR data itself. The separation in time of determining the aspect angle and acquiring the ISAR data, which occurs in previously known solutions, is thereby eliminated. Determining the aspect angle in the method according to the invention is no longer based on the location of the reflectivity distribution in the range Doppler segments, but analyzes only the position of the radiometric centroid in the distance and Doppler. The applicability is not limited to vehicles of constant velocity.