Hypercubes clustering: a machine learning method for efficiently finding
common sub-trajectories in spatiotemporal space and constructing
trajectories models for prediction
Abstract
Common sub-trajectory clustering is to find similar trajectory segments.
Existing clustering methods tend to overlook many of the relevant
sub-trajectories; others require a road network as input; all are
significantly slowed down considerably by large datasets. This study
proposes a novel machine learning approach, called Hypercubes
clustering. Hypercubes clustering transforms trajectories into a set of
Hypercubes. This study further applies Hypercubes clustering to solving
the Estimated Time of Arrival (ETA) problem to show a practical use.
ETA, which is used to predict the travel time of a given GPS trajectory,
has been extensively used in route planning. Deep learning has been
widely applied to ETA prediction. However, prediction tasks involve some
challenges, such as small data size, low precision of GPUs, high
training loss, and low accuracy. In the training phase, a trajectory
model is established using historical trajectories. In the prediction
phase, ETA is calculated according to the model. The software of this
study for ETA prediction is named HyperETA. The performance of
Hypercubes clustering was compared with that of grid clustering (i.e.,
constant time technique) in terms of memory usage, computational speed
and compared with a state-of-art method, TraClus, by assessing their
accuracy. The results of HyperETA are compared with a
deep-learning-based ETA method, called DeppTTE. The experiment results
show that Hypercube clustering can identify common sub-trajectories more
swiftly and with less memory usage than grid clustering. The accuracy of
Hypercube clustering and HyperETA is superior to TraClus and DeppTTE,
respectively. A few problems associated with deep learning are discussed
in this study.