Probe Data Normalization for Street Path Identification
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Solution Overview
Problem
Extracting street centerlines from probe traffic data is challenging due to noise variations, particularly around freeways, which disrupts the thresholding process and leads to loss of automatization and inaccurate segmentation.
Innovation Solution
A method that normalizes aggregated mobile device traffic data by computing gradients and identifying local maxima, amplifying surrounding areas orthogonal to the gradient direction, and using cumulative amplification values to determine travel paths, thereby avoiding thresholding issues and enhancing the detection of both major and minor streets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed threshold is used for segmentation, then the processing is simple and automated, but the results are inaccurate due to noise variations around freeways
Solution Approach 1:
The patent transforms the fixed threshold parameter into a dynamic gradient-based parameter. Instead of using a constant threshold value, the system computes gradients at each pixel location and determines threshold values relative to local gradient magnitudes. This allows the segmentation to adapt to local variations in traffic density, accurately separating streets from noise around freeways while maintaining automation through algorithmic gradient computation.
2Measurement precision
If manual threshold adjustment is used to avoid noise, then segmentation accuracy improves, but automatization is lost
Solution Approach 1:
The patent implements self-service by enabling the segmentation algorithm to automatically adjust its own threshold parameters based on the input data characteristics. The gradient computation and local maximum detection mechanisms allow the system to autonomously identify appropriate threshold values for each region without human intervention. The algorithm serves itself by using the data's own gradient structure to determine segmentation criteria, eliminating the need for manual threshold tuning while maintaining high accuracy.
3Measurement precision
If amplification is applied to all map areas, then small streets are detected, but noise around freeways is also amplified
Solution Approach 1:
The patent applies local quality by making the amplification factor spatially variable rather than uniform. The amplification is determined by local gradient characteristics and proximity to detected local maxima, creating different amplification zones across the map. Areas near identified street patterns receive higher amplification to enhance detection, while regions dominated by freeway noise receive different treatment. This localized approach allows small streets to be detected while preventing uniform amplification of noise artifacts.
Data Source
AI summary
Some embodiments provide a method for defining travel paths in a map region. The method identifies location data collected over a period of time from multiple mobile devices. The method aggregates the location data for each of multiple map areas. The aggregated data for each map area identifies an amount of mobile device traffic passing through the map area over the period of time. The method normalizes the aggregated data for a subset of the multiple map areas based on analysis of the relative amounts of mobile device traffic. The method uses the normalized data to identify paths in the map.


