Geomagnetic indoor positioning without hardware - the reality of a flawed system

It has been claimed that a low-cost of ownership Indoor Positioning System (IPS) can be achieved, without hardware, by exploiting the earth’s geomagnetic field.

In theory, geomagnetism could deliver an accurate indoor positioning solution without the expense of purchasing, installing, and maintaining infrastructure equipment. Unfortunately practical, real-world results don’t bear out the theory.

Several companies have thrown their hats in with geomagnetic positioning systems, promoting the obvious benefit of low cost, which can be as little as 20% of other solutions such as BLE (Bluetooth low energy) and Wi-Fi.

geomagnetic-banner

So how have they fared, and has the truth finally caught up with the hype? In this article, we’ll explore:

  • The theory behind a geomagnetic indoor positioning system.
  • How a geomagnetic system is set up.
  • The one advantage and some disadvantages of a geomagnetic system.
  • Real-world results with geomagnetic (the proof of the pudding).
  • Our inescapable conclusion.

How geomagnetic positioning works in theory

The earth’s magnetic field is a naturally occurring phenomenon. When it passes through the steel structure of a building and certain electrical equipment, each location in a room will have a unique magnetic field signature. Using these specific features to build a dataset, referred to as the building's “geomagnetic fingerprint” or “fingerprinting map”, implies geomagnetic positioning could be used for indoor positioning and navigation purposes.

The Earth’s magnetic field (the geomagnetic field). Source: ResearchGate

IPS using geomagnetic positioning technique. Source: ExtremeTech

 

In theory, it should be possible to construct an indoor localization platform based on fingerprinting a building’s geomagnetic field utilizing the built-in magnetic sensor (the compass) as well as other sensing technologies within a smartphone. This approach would negate any physical infrastructure requirement and thus reduce the set-up cost. Individual buildings could be identified by the unique magnetic disturbance their steel infrastructure creates, issues caused by local magnetic variations could be compensated for, and user devices (such as cellphones) could be located.

That’s the theory, now let’s explore setting up and locating devices, before moving on to the reality behind geomagnetic positioning.

Setup and locating devices

Setting up a geomagnetic positioning system involves someone surveying the location for geomagnetic signals at multiple points and creating a radio "map" or "dictionary". 

Once set up, when someone visits the location you look at the geomagnetic signals their cellphone is picking up and compare them to the map that was created previously.

You then know that if their device is detecting signals X, Y, and Z and if the radio map picked up the same signals, with the same strength, at point A, then the user must therefore be at that same position.

fingerprinting map 1

Utilize magnetic field features to build a fingerprint map.

Source: A New Fingerprinting Database for Indoor Localization

The advantage and disadvantages of geolocation

When looking at the advantages and disadvantages of geolocation, it’s important to appreciate that the advantages are purely theoretical. In effect, geolocation doesn’t work as theorized and the main selling point of a system that doesn’t require hardware has always cost.

Advantage

Cost - if geolocation worked effectively, the biggest advantage would be cost. Because there’s no hardware to install, a geolocation positioning system costs a fraction (about one-fifth the cost) of alternative BLE and Wi-Fi systems.

However,

Disadvantages

Inaccuracy - geomagnetic systems don't work efficiently. Their accuracy may be sufficient on the day they're set up, and the fingerprinting initially done, but their usability quickly deteriorates, which negates and overwhelms any initial "cost-benefit". When parts of your building are remodeled, or any significant changes are made to the layouts and furniture in the building, you need to re-survey and calibrate the system all over again if you want a positioning system that's anywhere near usable.

This is because indoor geomagnetic positioning relies on "geomagnetic fingerprint" datasets recorded at multiple points and stored in an IPS database to measure the indoor magnetic field. In addition, geomagnetic IPS technology utilizes the built-in magnetic sensor (compass) in smart mobile devices, which is notoriously inaccurate (see Fig. 1), compounding the issue with geomagnetic and precise blue dot orientation.

Fig. 1: Compared to Pointr’s Deep Location®, solutions that rely upon a smartphone’s built-in “compass” show relatively inconsistent orientation.

 

  • Scalability - geomagnetic is not scalable; every part of a building needs to be manually mapped, meaning the bigger the building, the bigger headache you’re creating for yourself in the long run. Geomagnetic requires constant maintenance as it needs an onsite survey and re-recording every time there's a venue change.
  • Functionality - geolocation doesn’t run in the background on iOS which means you can’t serve contextual notifications on iPhone, and you can’t collect customer flow data while the user’s cell phone is in their pocket. BLE, on the other hand, supports both.
  • Unreliability - the local magnetic field, and therefore the accuracy, is affected by moving metal objects like lifts or metal cabinets. Even with regular (and costly) re-configuration, it’s impossible to mitigate for factors like this.

Attribute

Pointr Deep Location®

Geomagnetic 

Location accuracy

< 1-3 meters

Consistent real-time accuracy

(patented)

< 1-3 meters

When first setup, if layout changes then accuracy drop

Orientation

Smooth (compass-free)

(patented)

Inaccurate

(compass)

Floor detection

Highly accurate

(patented)

Inaccurate

(jumps to wrong floors)

Time to deploy

Hours

(patented)

Weeks or months

(on-site survey/ recording needed)

Upkeep

None

(patented)

Regular maintenance

(on-site survey/ recording needed)

Setup cost

$$

 

$

(increase when add-on sensors involved)

 

Compass
Indoor positioning systems that rely on compass can be highly unreliable in orientation.

 

The proof of the pudding

At Pointr, we have practical experience of geomagnetic positioning systems not living up to their promise, in fact, not performing at all.

Several companies had been advertising that you don’t need any hardware to achieve accurate positioning with geomagnetic, ultimately their disappointed customers reached out to Pointr to address their issues. Here are a few examples.

  • A shopping mall group in Hong Kong asked us to fix their accuracy after they were told “you don't need hardware" with geomagnetic positioning. When they found the lack of accuracy unusable, they were told that beacons could be installed to improve it - completely defeating the purpose of a “non-hardware” system. After 5-6 years, the company that installed the system is now honest about it and mentions this on their website. An Indian Airport came to us after a similar experience.
  • Another mall operator in Canada considered Pointr for their indoor positioning needs but went with a competitor recommending a geomagnetic solution for only 20% of our price. Three months later they came back to us to ask if we could fix it. Again, the option to install BLE beacons was also offered by their supplier to improve accuracy.
  • A famous New York department store had a bad experience with geomagnetic and ultimately chose Pointr for our accuracy, functionality, and scalability.

We have many more cases like this that back up the issues associated with geomagnetic highlighted in this article.

So, it seems we must conclude…

While on the face of it a geomagnetic system may seem an attractive solution to indoor positioning, mainly because of its low cost and lack of hardware requirements, that’s not the whole story. The accuracy of systems that have been attempted has been proven to deteriorate over time with many clients realizing, only after the fact, that the solution they’ve been sold was not fit for purpose.

It’s also troublesome that the future of support for geomagnetic systems is in doubt. This uncertainty strongly suggests that a geomagnetic solution for indoor positioning is just not worth the gamble.

Next moves

It’s clear that an indoor positioning solution that doesn’t rely on geomagnetic is preferable to one that has an unreliable and unscalable technology at its core.

Pointr’s Deep Location® is such a solution. We don’t use smartphone compasses or fingerprinting and we’re scalable to thousands of venues at speed, something that definitely can’t be said of geomagnetic.

Pointr’s Deep Location® technology is live in 27 countries and over 3000 venues.

Talk to us today and start your indoor positioning journey with Pointr.

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Author: Les Blythe, Eva Cheng

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