Laser Scanner Control for Sunlight Noise Reduction
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Solution Overview
Problem
Existing Mobile Mapping Systems (MMS) using laser scanners face challenges in reducing noise points, particularly from sunlight, which are mistakenly detected as measured light, requiring complex and time-consuming post-processing methods to filter out noise from point clouds.
Innovation Solution
A device and method that calculates the direction of the sun, measures brightness, and sets scan conditions to restrict laser scanning in the sun's direction when brightness exceeds a threshold, inhibiting emission or detection of sunlight as measured light, thereby reducing noise in point cloud data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser scanning is performed in all directions without restriction, then complete point cloud data coverage is obtained, but sunlight is mistakenly detected as measured light creating noise in the point cloud
Solution Approach 1:
The system calculates the sun's position in advance and determines scan restriction areas before performing laser scanning. By pre-identifying directions where sunlight would interfere with measurements, the system prevents misdetection of sunlight as measured light, thereby improving point cloud data accuracy while avoiding noise contamination
Solution Approach 2:
The brightness of the sky in potential scan directions is measured before actual laser scanning occurs. This preliminary brightness measurement allows the system to identify and restrict scanning in directions where sunlight intensity exceeds thresholds, preventing noise generation in the point cloud data before it occurs
2Measurement precision
If post-processing filtering is applied to remove noise points, then noise reduction is achieved, but processing time increases and complexity increases
Solution Approach 1:
The system performs sun position calculation and scan restriction area determination before laser scanning begins. By pre-identifying and restricting scan directions that would generate sunlight noise, the system prevents noise generation at the source rather than requiring time-consuming post-processing filtering, thereby reducing overall processing time while maintaining measurement precision
Solution Approach 2:
The system extracts and removes the problematic scan directions (those pointing toward the sun) from the overall scanning plan before data collection. By excluding sunlight-prone directions from the scan pattern entirely, the system eliminates noise generation at the source, avoiding the need for subsequent noise filtering operations and reducing processing time
3Measurement precision
If laser scanning is restricted in sun direction, then sunlight misdetection is reduced, but data coverage in that direction is lost
Solution Approach 1:
The system applies scan restriction only to specific local directions where the sun is located, rather than restricting the entire scanning area. By calculating the precise sun position and limiting restrictions only to those specific angular regions, the system minimizes data coverage loss while effectively preventing sunlight misdetection in the problematic directions
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
Significantly reduces the misdetection of sunlight as noise in point clouds, simplifying the process by preventing laser scanning in areas with high sunlight intensity and minimizing the generation of noise, thus improving data accuracy and efficiency.
Implementation Method 1
a laser scanner (LIDAR)... a laser scanner that emits laser light and detects the reflected light to thereby measure three-dimensional positions of objects
Implementation Method 2
a brightness measuring unit that is configured to measure the brightness of an image that contains the direction of the sun
Data Source
AI summary
Detection of sunlight as noise is avoided in obtaining point clouds by using a laser scanner. A laser scanner controlling device includes a sun direction calculating unit 115, a brightness measuring unit 116, and a scan condition setting unit 118. The sun direction calculating unit 115 calculates the direction of the sun. The brightness measuring unit 116 measures the brightness of an image that contains the direction of the sun. The scan condition setting unit 118 sets a condition for restricting laser scanning in the direction of the sun when the brightness is not less than a predetermined threshold value.