How Google May Identify Device Locations Using Magnetic Fields from AC Powerlines

Posted @ Jan 26 2017 by


The Value of Knowing Location of Searchers to a Search Engine

There are many reasons why it might be helpful for a search engine to know the location of a device that is performing a search, such as helping in location based searches or determining the best locations to take photographs at or identifying businesses or landmarks at specific locations. There are some methods that I have read about that a Google might use to identify the location of a device, such as Global Positioning Satellite services or using a combination of sensors and wireless access points, but we came across a new approach in a patent granted to Google today.

Google was granted a patent for using magnetic fields generated by alternating current power lines to determine the location of a device.

The patent describes how magnetic fields surround alternative current power lines might be mapped, and a magnetometer in a device might track those magnetic fields to identify the location of the device within such maps.

Using magnetic fields in a manner such as this has benefits over relying upon GPS or Wifi signals.

Knowledge of the location of a device can help with things such as navigation, data collection, self-driving vehicles, or other tasks where knowledge of the location of a device is beneficial.

Limitations of Other Positioning Systems and Sensors

(1) We are told that GPS can fail to provide location determination when that a device is located within a building. GPS signals from satellites may have difficulties penetrating the walls of a building and making it to a device, making a precise location. difficult to ascertain.

(2) Wifi can overcome limitations of navigation such as GPS failing to properly operate in an indoor environment, it also has some limitations. WiFi navigation relies on signal strength measurements and those signals can be reflected by metallic objects and absorbed by other objects. WiFi signal strengths can fail to provide precise measurements as well because they are not accurately predictable in practice, especially in crowded indoor environments.

(3) Another device location that is of concern is car navigation systems, which may have troubles with severe weather. We are told that optical sensors in a self-driving car system may operate at less that helpful efficacy because of when rain, snow, road salt, or other contaminants obscure the sensor. Environmental factors such as deep snow drifts could also reduce the system functionality.

Magnetic Fields a Solution?

The patent points to a possible solution in determining location using magnetic field readings. a Magnetometer could provide readings of a magnetic field collected by a magnetometer. A computing device could identify aspects of those magnetic fields, by magnetic fields created at a frequency at which electrical power is transmitted along one or more power lines. A map of magnetic fields could be consulted to identify where that device is located. The description of the patent provides many more details about how such magnetic fields operate around power lines, and how they might be used to determine locations. The patent is:

Determining location using magnetic fields from AC power lines
Inventors: Gregory Peter Kochanski
Assignee: Google Inc.
United States Patent 9,551,561
Granted: January 24, 2017
Filed: February 20, 2014


Systems and methods for determining location using magnetic fields from AC power lines are provided. As an example, each magnetic field reading collected by the device over time can be analyzed to determine a plurality of characteristics of the magnetic field. One or more of the plurality of characteristics can describe a component of the magnetic field that oscillates at a frequency associated with the AC power lines. The plurality of characteristics can be compared to expected values respectively associated with a plurality of locations and provided by a map of the magnetic field to determine a location at which each magnetic field reading was collected. In further embodiments, magnetic field readings collected by the device over time can be analyzed in conjunction with other data or constraints to determine a trajectory of the device. In addition, the map can be updated using the collected readings and the determined trajectory.


I’m reminded of a search engine crawling program finding aspects and elements of the Web to help it index content on web pages. In this case, it is the search engine mapping aspects of the world around us (power lines, and the magnetic fields around those) that can be used to identify locations that can help devices become aware of their locations, and share that information to provide services, including search and navigation, and location-based services. To end this post with a pun (I can’t help myself), it is a shocking solution.

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