Indoor location sensing using geo-magnetism

TLDR

Structural steel in buildings warps the geomagnetic field spatially while remaining temporally stable. The authors present an indoor positioning system that uses magnetic field disturbances from structural steel to determine location and explore constraint techniques to sustain accuracy as the sample space grows. The system localizes by measuring the magnetic field with an array of e‑compasses, comparing the readings to a pre‑mapped magnetic map, and applying constraint techniques to maintain accuracy. Experiments in two buildings across multiple floors show the system achieves within‑1‑meter accuracy 88 % of the time.

Abstract

We present an indoor positioning system that measures location using disturbances of the Earth's magnetic field caused by structural steel elements in a building. The presence of these large steel members warps the geomagnetic field in a way that is spatially varying but temporally stable. To localize, we measure the magnetic field using an array of e-compasses and compare the measurement with a previously obtained magnetic map. We demonstrate accuracy within 1 meter 88% of the time in experiments in two buildings and across multiple floors within the buildings. We discuss several constraint techniques that can maintain accuracy as the sample space increases.