An apparatus for the quantification of privacy risk in geographic data for probe devices in a geographic region includes a database, a sub-trajectory module, a candidate list calculator, and a provision module. The database is configured to store trajectory data based on sequences of sensor measurements. The sub-trajectory module is configured to receive trajectory data points based on sequences of sensor measurements of the probe devices collected in the geographic region and determine sub-trajectories from changes in trajectory identifiers. The candidate list calculator is configured to concatenate at least two of the sub-trajectories based on at least one concatenation parameter. The provision module is configured to calculate a reconstruction rate in the trajectory data and provide the reconstruction rate for a quantification of privacy risk to an external device.