DC electromagnetic tracking
Direct current (DC) electromagnetic tracking is a kind of electromagnetic 3D tracking that uses pulsed signals, and subtracts the earth's magnetic field from each, to get measurements.
DC trackers are suitable for use near aluminum and copper.[1] However, Ascension claims that DC trackers typically report one-fifth the errors of a AC system in real-world settings containing steel rebar in floors and ceilings, but admits that ferrous objects within a few feet of a tracking area can be a problem.[2]
For a pulsed-DC tracking systems operating at 400Hz, the skin depth of aluminum is 0.165 inch. Thus, aluminum thicker than 0.165 inch distorts the magnetic fields and makes tracking inaccurate.[3]
DC tracking was developed and patented by Ascension to overcome some of the limitations of AC electromagnetic tracking, specifically the metallic distortion problems.[2]
Ascension claims that DC tracking technology is 3 to 10 times less impacted by conductive metal than AC technology.[2]
DC trackers have problems near ferrous metals, such as iron.[1]
How it works[edit]
Each transmitting antenna component (X, Y, or Z) is driven one at a time by a pulsed, direct current signal. The receiving antennas measure the values of transmitted direct current magnetic fields one dimension at a time and those of the Earth's magnetic field as well, one dimension at a time.[4]
References[edit]
- ↑ 1.0 1.1 Menache, AuthorsAlberto (2011-01-01). "Understanding Motion Capture for Computer Animation". https://www.sciencedirect.com/book/monograph/9780123814968/understanding-motion-capture-for-computer-animation.
- ↑ 2.0 2.1 2.2 "The Advantage of DC Magnetic Tracking". https://web.archive.org/web/19970714033826if_/http://www.ascension-tech.com/dcadvantage.htm.
- ↑ "US Patent US7761100". https://patentimages.storage.googleapis.com/35/d5/a6/9085c9e9991319/US7761100.pdf.
- ↑ "The first DC electromagnetic 3D tracking system patent". https://patentimages.storage.googleapis.com/18/64/9d/900cb662e909bb/US4849692.pdf.