GraCT: A Grammar based Compressed Representation of Trajectories

Nieves Brisaboa, Adriá Gómez-Brandón, Gonzalo Navarro, and José Paramá

We present a compressed data structure to store free trajectories of moving objects (ships over the sea, for example) allowing spatio-temporal queries. Our method, GraCT, uses a k^2-tree to store the absolute positions of all objects at regular time intervals (snapshots), whereas the positions between snapshots are represented as logs of relative movements compressed with Re-Pair. Our experimental evaluation shows important savings in space and time with respect to a fair baseline.