Abstract
Low-cost GPS (receiver) has become a ubiquitous and integral part of our daily life. Despite noticeable advantages such as being cheap, small, light, and easy to use, its limited positioning accuracy devalues and hampers its wide applications for reliable mapping and analysis. Two conventional techniques to remove outliers in a GPS trajectory are thresholding and Kalman-based methods, which are difficult in selecting appropriate thresholds and modeling the trajectories. Moreover, they are insensitive to medium and small outliers, especially for low-sample-rate trajectories. This paper proposes a model-based GPS trajectory cleaner. Rather than examining speed and acceleration or assuming a pre-determined trajectory model, we first use cubic smooth spline to adaptively model the trend of the trajectory. The residuals, i.e., the differences between the trend and GPS measurements, are then further modeled by time series method. Outliers are detected by scoring the residuals at every GPS trajectory point. Comparing to the conventional procedures, the trend-residual dual modeling approach has the following features: (a) it is able to model trajectories and detect outliers adaptively; (b) only one critical value for outlier scores needs to be set; (c) it is able to robustly detect unapparent outliers; and (d) it is effective in cleaning outliers for GPS trajectories with low sample rates. Tests are carried out on three real-world GPS trajectories datasets. The evaluation demonstrates an average of 9.27 times better performance in outlier detection for GPS trajectories than thresholding and Kalman-based techniques.
Highlights
IntroductionLow-cost, non-professional GPS (receiver) has become popular and grows in popularity at an ever increasing rate
Low-cost, non-professional GPS has become popular and grows in popularity at an ever increasing rate
Compared with professional GPS, low-cost GPS has advantages of easy use and portability. These GPS-enabled devices are found useful in online mapping [1], traffic management [2], and localization of places of interest [3], their accuracy is limited due to existence of outliers
Summary
Low-cost, non-professional GPS (receiver) has become popular and grows in popularity at an ever increasing rate. Compared with professional GPS, low-cost GPS has advantages of easy use and portability These GPS-enabled devices are found useful in online mapping [1], traffic management [2], and localization of places of interest [3], their accuracy is limited due to existence of outliers. Erroneous or missing GPS readings may be caused due to various reasons, such as obscured line of sight, device cold starts, and other satellite signal disruptions [4,5,6]. Such aberrant data with inherent inconsistency may lead to difficulties, mistakes, or even failures in subsequent processing such as route prediction [7] and trajectory clustering [8].
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