Title: Semi-automated Signal Surveying Using Smartphones and Floorplans,
Abstract: Location fingerprinting locates devices based on pattern matching signal
observations to a pre-defined signal map. This paper introduces a technique to
enable fast signal map creation given a dedicated surveyor with a smartphone
and floorplan. Our technique (PFSurvey) uses accelerometer, gyroscope and
magnetometer data to estimate the surveyor's trajectory post-hoc using
Simultaneous Localisation and Mapping and particle filtering to incorporate a
building floorplan. We demonstrate conventional methods can fail to recover the
survey path robustly and determine the room unambiguously. To counter this we
use a novel loop closure detection method based on magnetic field signals and
propose to incorporate the magnetic loop closures and straight-line constraints
into the filtering process to ensure robust trajectory recovery. We show this
allows room ambiguities to be resolved.
An entire building can be surveyed by the proposed system in minutes rather
than days. We evaluate in a large office space and compare to state-of-the-art
approaches. We achieve trajectories within 1.1 m of the ground truth 90% of the
time. Output signal maps well approximate those built from conventional,
laborious manual survey. We also demonstrate that the signal maps built by
PFSurvey provide similar or even better positioning performance than the manual
signal maps.