UAV Aerial Photography Image Unification via Feature Point Alignment

Solution Overview

Problem

Aerial photograph image pickup methods using small UAVs face challenges in achieving accurate three-dimensional measurements due to image distortion caused by tilting and unstable optical axes, which affects the accuracy of digital photogrammetry and stereo-image combination.

Innovation Solution

The method involves acquiring still images along meandering routes with high overlapping ratios and using relative orientation and feature points to create stereo-images in coordinated systems, with GPS-based measurements and bundle adjustments to correct and unify the images, ensuring accurate three-dimensional representation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If still images are acquired by a fixedly mounted image pickup device on a small UAV, then the device can be mounted on a lightweight flying object, but the optical axis becomes tilted and unstable due to wind and body movement

Engineering Contradiction:

ImproveUAV weightVSAvoidoptical axis stability

Core Design Contradiction:

Weight of moving objectVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary action by extracting common feature points from overlapped image portions before combining images. The system identifies tie points in advance from the meandering flight path images, then uses these pre-identified points as reference for accurate image combination, compensating for the tilted and unstable optical axis caused by lightweight UAV body movement.

Inventive Principle:

Principle #10Preliminary action

2Area of stationary object

If images with tilted and variable optical axes are sequentially combined, then wide range coverage is achieved, but the resultant image becomes distorted and curved

Engineering Contradiction:

Improveimage coverage areaVSAvoidimage combination accuracy

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent implements feedback by using common feature points (tie points) extracted from overlapped image portions as reference information. These tie points provide feedback on the actual positional relationships between images taken during meandering flight, allowing the system to correct distortions and curvings in the combined image by adjusting the combination process based on the actual feature point positions.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If conventional image combination methods are used with meandering flight paths, then flight flexibility is maintained, but tie point extraction becomes difficult and measurement accuracy decreases

Engineering Contradiction:

Improveflight path flexibilityVSAvoidthree-dimensional measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by extracting common feature points from overlapped image portions before combining images. The system identifies tie points in advance from the meandering flight path images, then uses these pre-identified points as reference for accurate image combination, compensating for the tilted and unstable optical axis caused by lightweight UAV body movement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by using common feature points (tie points) extracted from overlapped image portions as reference information. These tie points provide feedback on the actual positional relationships between images taken during meandering flight, allowing the system to correct distortions and curvings in the combined image by adjusting the combination process based on the actual feature point positions.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP2597422B1Aerial photograph image pickup method and aerial photograph image pickup apparatus

Publication Date: 2019.09.25 TOPCON CORPORATION

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AI summary

An aerial photograph image pickup method comprises a first step of acquiring still images along an outward route and a return route respectively when a flying object (1) flies in meandering manner in the sky over an object range to be measured, a second step of preparing a stereo-image by relative orientation on one set of images adjacent to each other with regard to three images adjacent to each other in advancing direction, and of preparing another stereo-image by relative orientation on one more set of adjacent images and of preparing two sets of stereo-images, a third step of connecting two sets of stereo-images by using feature points extracted from a portion of an image common to two sets of stereo-images and the portion is an overlapped portion of the three images all together, a step of connecting all stereo-images in outward route direction and in return route direction according to images acquired in the first step by repeating the procedures of the second step and the third step, a step of selecting common tie points from the images adjacent to each other in the adjacent course and of connecting the adjacent stereo-images in the course, and the aerial photograph image pickup method prepares an unified stereo-image which covers the entire object range to be measured and is represented by common three-dimensional coordinate system.