Laser Hydrography Local Inclination Refraction Correction
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Solution Overview
Problem
Conventional laser hydrography methods suffer from low measurement resolution due to large laser beam diameters, which limits the accuracy of water surface and bottom measurements, resulting in a coarse grid of measurement points with low range resolution.
Innovation Solution
The method determines the local inclination of the water surface at the entry point of the laser beam using at least three measurement points, allowing for the calculation of a local entry angle and accounting for optical refraction, enabling the use of tightly focused laser beams with small diameters to achieve higher spatial and range resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large laser beam diameters (2-5 m) are used on the water surface, then the water surface can be assumed flat and horizontal, but the measurement resolution and range resolution are greatly limited
Solution Approach 1:
The patent segments the water surface into multiple local measurement zones, each with its own inclination characteristics. By dividing the large beam area into smaller sub-areas and calculating local inclinations for each, the system achieves higher measurement resolution while managing complexity through localized rather than global calculations.
Solution Approach 2:
The patent applies partial action by calculating local inclinations only at specific entry points where measurements are needed, rather than computing the entire water surface geometry. This selective approach reduces computational complexity while maintaining measurement precision where it matters most.
2Area of stationary object
If large laser beam diameters are used, then coverage area is increased, but the measurement-point density and range resolution are reduced
Solution Approach 1:
The patent applies local quality by treating different regions of the laser beam footprint differently. Instead of assuming uniform flatness across the entire beam area, the system calculates specific local inclinations at entry points, allowing high measurement-point density in critical areas while maintaining broad surface coverage.
3Measurement precision
If tightly focused laser beams with small beam diameters are used, then measurement resolution is improved, but the local inclination of the water surface must be determined to account for wave motion
Solution Approach 1:
The patent applies preliminary action by calculating the local inclination of the water surface before performing the main depth measurement. By determining the surface inclination at the entry point in advance, the system can pre-correct for refraction effects, simplifying the subsequent depth calculation and improving overall measurement accuracy.
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
This approach significantly increases measurement accuracy and resolution, allowing for a denser arrangement of measurement points and improved data capture rates, enabling more precise determination of water surface and bottom topography.
Implementation Method 1
the optical refraction due to the corresponding entry angle of the laser beam
Data Source
AI summary
Method for laser hydrography in which at least one laser beam is emitted from a known location and in a known direction onto the surface of a body of water and through the water onto the bottom of the body of water and measurement points of the water surface and the water bottom in a coordinate system are determined from transit-time measurements of the reflections of the laser beam at the water surface and water bottom, wherein the local inclination of the water surface at an entry point of the laser beam into the body of water is determined from at least three measurement points of the water surface, wherein a local entry angle of the laser beam into the body of water is determined from the local inclination and the known direction of the laser beam, and wherein the measurement point of the water bottom is created as a function of the laser beam direction, the local inclination, and the optical refraction due to the corresponding local entry angle of the laser beam.