Surveying Instrument Camera Eccentricity Compensation

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Solution Overview

Problem

In surveying instruments with a camera eccentric to the rotation center, determining the correct direction from the rotation center to a target is challenging without knowing the distance, as the camera and rotation center are non-coincident, making direct direction determination from the camera image inadequate.

Innovation Solution

Capturing two images from different camera positions and orientations, using camera calibration data to determine target coordinates relative to the rotation center, allowing for accurate direction and distance determination from the rotation center to the target.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a camera is used in a surveying instrument to capture images for target identification, then user convenience and target selection capability are improved, but measurement precision deteriorates when the camera center and rotation center are non-coincident

Engineering Contradiction:

Improvetarget selection capabilityVSAvoiddirection determination accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical alignment requirement (camera center coinciding with rotation center) with a computational solution. By using image coordinates from the camera and applying mathematical transformations based on known eccentricity parameters, the system calculates accurate direction angles from the rotation center without requiring physical realignment of the camera with the rotation axis.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces intermediate computational parameters (image coordinates, eccentricity offsets, and transformation equations) as mediators between the camera's optical axis and the rotation center. These intermediate calculations bridge the gap between the non-coincident centers, enabling accurate target direction determination despite the physical separation between camera and rotation center.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the camera center and rotation center are positioned separately (eccentric arrangement), then device design flexibility is improved, but direction determination accuracy deteriorates

Engineering Contradiction:

Improvedesign flexibilityVSAvoiddirection determination accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent transforms the physical parameter problem (camera position relative to rotation center) into a computational parameter solution. By incorporating eccentricity parameters (offset distances in x and y directions) into the calculation model, the system maintains design flexibility for separate camera and rotation center positioning while achieving accurate direction determination through parameter-based corrections in the coordinate transformation equations.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If distance to target is unknown, then measurement process simplicity is maintained, but coordinate determination accuracy deteriorates

Engineering Contradiction:

Improvemeasurement process simplicityVSAvoidtarget coordinate accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent performs preliminary determination of direction angles from the rotation center to the target using only image coordinates and eccentricity parameters, before distance measurement is completed. By calculating the angular direction first through coordinate transformation, the system enables accurate target positioning and coordinate determination without requiring prior knowledge of the target distance, thus maintaining process simplicity while achieving accuracy.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP2247921B1Determining coordinates of a target in relation to a survey instruments having a camera

Publication Date: 2014.10.08 TRIMBLE AB

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AI summary

A method is disclosed for determining coordinates of a target in relation to a surveying instrument wherein a first image is captured using a camera in a first camera position and orientation, a target is selected by identifying an object point in the first image, and first image coordinates of the object point in the first image are measured. The surveying instrument is then rotated around the rotation center so that the camera is moved from the first camera position and orientation to a second camera position and orientation, while retaining the rotation center of the surveying instrument in a fixed position. A second image is captured using the camera in the second camera position and orientation, the object point identified in the first image is identified in the second image, and second image coordinates of the object point in the second image are measured. Target coordinates in relation to the rotation center of the surveying instrument are then determined based on the first camera position and orientation, the first image coordinates, the second camera position and orientation, the second image coordinates, and camera calibration data. Furthermore, a surveying instrument for performing the method is disclosed.