Sight Axis Calibration Using Map Landmarks for Compass Error
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Solution Overview
Problem
Existing terrestrial observation devices suffer from inaccuracies in determining the orientation of the sight axis due to magnetic field disturbances, which are not effectively compensated by current calibration methods, requiring additional sensors and strict control.
Innovation Solution
A method that utilizes a digital magnetic compass, satellite receiver, and laser range finder to calibrate the orientation by displaying a mapping-image, allowing users to correct the sight axis orientation based on geographic coordinates and landmarks, compensating for errors without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors (gravitational field sensor, GNSS, inertial measurement unit) are used to compensate for magnetic compass errors, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses a mapping image (copy of the geographic environment) as a reference to identify landmark positions and calculate orientation corrections. Instead of adding physical sensors, the system creates a virtual reference framework that can be compared against actual visual observations to determine compass errors and apply corrections.
2Measurement precision
If strict control is applied during calibration to effectively compensate for magnetic field disturbances, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The system performs self-calibration by automatically comparing the magnetic compass orientation with the orientation derived from landmark positions on the mapping image. The processing unit autonomously calculates correction parameters without requiring manual intervention or strict operator control during the calibration process.
Solution Approach 2:
The system establishes a feedback loop where the mapping image serves as a reference, the actual orientation is measured by the magnetic compass, the difference is calculated as a correction parameter, and this correction is applied to improve subsequent orientation measurements. This continuous feedback mechanism enables automatic error compensation.
3Device complexity
If magnetic field disturbance compensation is implemented using only standard device sensors, then device complexity is reduced, but measurement precision deteriorates due to ineffective calibration methods
Solution Approach 1:
The patent introduces a mapping image as an intermediary reference that mediates between the magnetic compass measurement and the true geographic orientation. By using the known positions of landmarks on the mapping image as a reference framework, the system can indirectly determine orientation accuracy without adding complex sensors, achieving both simplicity and precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves the accuracy of measuring the orientation of the sight axis by enabling users to identify and correct errors using standard device sensors, enhancing precision and reliability.
Implementation Method 1
The digital magnetic compass is arranged to detect a magnetic field corresponding to the Earth's magnetic field
Implementation Method 2
The digital magnetic compass is susceptible to two types of magnetic field disturbances, which lead to errors in determining the magnetic North direction
Implementation Method 3
a range finder for determining a distance from a reference point being located on the sight axis
Data Source
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AI summary
Method for calibrating a terrestrial observation device (1) comprising a viewing member (3) defining a sight axis, a range finder (6) for determining a distance from a reference point being located on the sight axis, an orientation-measuring member (7) for measuring the orientation of the sight axis to determine a current orientation of the sight axis, a display unit (4) and an electronic processing unit (5). The method comprises the steps, commanded by the processing unit, of: displaying a mapping-image on the display unit, corresponding to a current position of the observation device; representing the current position and the sight axis from the current orientation on this mapping-image; having a user indicate, on the mapping-image, the reference point aimed at with the range-finder, and determining the position of the reference point indicated by the user on the mapping-image; and deducing from this, a correction parameter of the current orientation of the sight axis. Terrestrial observation device for implementing that method.