Satellite Image Cloud Removal Using Illumination-Normalized Interpolation

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Solution Overview

Problem

Satellite images are often obscured by clouds, which complicates applications like crop growth analysis and environmental surveys, and existing techniques for cloud removal, such as using radar-based images, are costly or unavailable, and illumination variations across images confuse changes in the scene due to illumination differences rather than actual landscape changes.

Innovation Solution

A method that interpolates cloudy portions of satellite images using a series of images taken over time, accounting for pixel availability and illumination normalization, by minimizing a quadratic equation to predict what was obscured by clouds, using cloud probabilities and availability scores to refine interpolation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If radar-based images are used to remove clouds, then cloud removal effectiveness is improved, but cost increases and availability decreases

Engineering Contradiction:

Improvecloud removal effectivenessVSAvoidcost and availability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses multiple inexpensive optical satellite images taken at different times instead of expensive radar images. By acquiring several low-cost optical images and selecting cloud-free portions from each, the system achieves reliable cloud removal without the high cost and limited availability of radar-based solutions

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent makes optical satellite images serve multiple functions: they provide both the primary imaging data and the reference data needed for cloud removal. By using the same optical imaging system for both capturing target images and reference images, the system eliminates the need for separate radar systems, reducing cost while maintaining cloud removal effectiveness

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Quantity of substance

If multiple satellite images taken under different illumination are used for cloud removal, then more cloud-free data is available, but illumination variations confuse scene changes

Engineering Contradiction:

Improveavailability of cloud-free pixelsVSAvoidaccuracy of scene change detection

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent extracts and removes illumination effects from satellite images before performing cloud removal. By separating illumination variations from actual scene content, the system can use multiple images with different lighting conditions without confusion, thereby increasing the quantity of usable cloud-free data while maintaining measurement precision

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary illumination normalization on all satellite images before using them for cloud removal. By pre-processing images to remove illumination effects in advance, the system ensures that subsequent cloud removal operations work with illumination-corrected data, allowing greater flexibility in selecting reference images while maintaining accuracy

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If simple interpolation is used to replace clouds, then computational complexity is reduced, but accuracy of cloud removal decreases

Engineering Contradiction:

Improvecomputational complexityVSAvoidaccuracy of cloud prediction

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent transforms the cloud removal problem from a simple spatial interpolation task to a multi-parameter optimization problem. By introducing parameters such as pixel availability scores, illumination normalization factors, and temporal weighting, the system achieves higher accuracy while managing computational complexity through efficient algorithms

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12555350B2Cloud removal by illumination normalization and interpolation weighted by cloud probabilities

Publication Date: 2026.02.17 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Clouds in a satellite image are replaced with a prediction of what was occluded by those clouds. The cloudy portion of the image is interpolated from a series of satellite images taken over time, some of which are cloud-free in the target image's cloudy portion. In some configurations, clouds are removed taking into account each pixel's availability—a measure of certainty that a pixel is cloud-free. Furthermore, these images may have been taken under different amounts of illumination, making it difficult to determine whether a difference between two images is due to a change in illumination or a change to the location. The effect of illumination on each image is removed before interpolating the cloudy portion of the image. In some configurations, removing the effect of illumination also takes into account pixel availability.