Cloud Detection in Aerial Imagery via Mutual Information
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Solution Overview
Problem
Aerial imagery often contains clouds that obscure earth surface details, making it difficult to assess cloud coverage due to visual similarities with other objects like snow or sea, and existing methods struggle to accurately identify clouds.
Innovation Solution
The method employs mutual information calculation between acquired and reference aerial images to determine cloud presence by comparing image variables, using processing circuitry to align, warp, and scale images for accurate similarity assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional visual identification methods are used to detect clouds in aerial images, then the detection process is simple, but the detection accuracy is low due to visual similarities between clouds and other objects like snow or sea
Solution Approach 1:
The patent introduces a reference aerial image as an intermediary element to facilitate cloud detection. By comparing the acquired aerial image with a reference image of the same geographic location, the system uses mutual information to identify cloud-covered regions. This intermediary reference image enables accurate cloud detection without relying solely on visual characteristics that can be ambiguous.
Solution Approach 2:
The patent transforms the cloud detection problem from visual pattern recognition to statistical parameter comparison. By calculating mutual information between corresponding pixels in the acquired and reference images, the system detects clouds based on information theoretic parameters rather than visual appearance, thereby improving accuracy despite increased computational complexity.
2Reliability
If cloud detection is performed to improve surveying usefulness, then the value of aerial imagery increases, but the processing time and computational resources increase
Solution Approach 1:
The patent performs preliminary actions by acquiring a reference aerial image of the same geographic location before or during the cloud detection process. This reference image is prepared in advance and stored, enabling rapid mutual information calculation when cloud detection is needed, rather than performing all processing from scratch each time.
Solution Approach 2:
The patent uses a reference aerial image as a copy or replica of the same geographic area under different conditions (ideally cloud-free). By comparing the acquired image with this reference copy, the system efficiently identifies clouds without needing to reprocess the entire image analysis pipeline, thereby reducing processing time while maintaining reliability.
Data Source
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AI summary
A method of detecting clouds in an acquired aerial image includes determining a region of a reference aerial image (2) corresponding to a region of an acquired aerial image (1). For each of a plurality of locations (6) over the region of the acquired aerial image and corresponding to a plurality of locations over the region of the reference aerial image, the mutual information of one or more variables associated with the location in the acquired aerial image and one or more variables associated with the corresponding location in the reference aerial image is calculated. Using the mutual information calculated for each of the plurality of locations over the region of the acquired aerial image, it is determined when the acquired aerial image displays a cloud (4) at the location in the region of the acquired aerial image.