Nivedit Majumdar Nivedit Majumdar

Sensors involved in Indoor Positioning Systems

Indoor Positioning Systems are generating a lot of buzz across various sectors, right from retail to workplaces to even hospitals. We are seeing a massive growth in the technologies involved, and with the involvement of big industry players such as Google, Apple and Microsoft – among others – things look all the more promising for the sphere of indoor positioning.

Location based marketing and alerts that are generated from contextually aware engines form the major contributing factors for the sphere of Indoor Positioning. But the most important one would have to be the hardware aspect of it all – sensors, which gather data about the users’ location, and constantly monitor the location changes.

So in this article, I’ll be talking about the sensors that are involved in Indoor Positioning System, and how they are turning out to be the major game changer as far as intuitive interaction between establishment owners and customers is concerned.


Indoor positioning, as the term quite evidently implies, refers to the process of tracking people within establishments in order to provide them relevant information and messages, in the form of contextually aware engines which study the user’s location. This can also be beneficial for the establishment owner to gauge the footfall and the customer interest depending on how much time they spend in particular locations, so it brings in a win-win situation like never before in the retail sector.

Now before we actually jump into the sensors involved, let’s take a broad overview of the stimuli that are actually sensed. There are two main stimuli: proximity based, and position based.


The proximity based options involve tiny transmitting sensors which are placed at strategic locations within the establishment. Termed as beacons, these devices run primarily on Bluetooth Low Energy, however NFC enabled beacons are also popular. This technique would be beneficial in cases wherein alerts and notifications are sent to the user’s smartphone based on his/her proximity from a particular item within the store, and this also facilitates proximity based messages – which marketers can truly take advantage of.

(Image Source: Air Patrol Corp)

Position based strategies involve taking into account the specific location of the customer as he/she travels through the store. It involves broader sensing algorithms, as opposed to the proximity based options. The benefit in this particular scheme is primarily for the establishment owner, as footfall analysis and customer buying behaviours can be easily gauged through this scheme.

(Image Source: Air Patrol Corp)


For a broad overview of the topic, this classification is alright. But this is just the tip of the iceberg, and a deeper insight reveals a lot more technologies in store.


One thing has to be clearly understood : when it comes to real time indoor positioning, one can’t rely wholly on GPS systems alone. Coverage and access to the satellites plays a defining factor, and GPS is rendered almost useless when the user is within a particular building.

Of course, fused location and geofencing techniques are beneficial, but they work properly only outdoors. And this limits the scope to a very narrow range, since ultimately, people spend more time indoors rather than outdoors. Ultimately, this calls for more robust measures to gauge the user’s location while he/she is indoors, and contextually provide him with content which might be relevant and enhance the overall experience.

(Terminology Source: RX Networks)



Again, the beacons which were used to gauge the proximity of the patrons can also be used as a crude measure to gather the position indoors. This is accomplished via a reference framework of known beacon locations such as WiFi access points, NFC tags or even cellular towers, besides the BLE beacons, of course.


I’ve already spoken in detail about sensors and the huge impact that they are having on Context and the Quantified Self, and they play a major role in Indoor Positioning as well. Gyroscopes and acclerometers in smartphones maintain position changes in reference to a previous position reading, but they are still – at the end of the day – two dimensional in nature. What this means, is that they tend to drift after about a minute unless reset by an external beacon reference.

This is where things get interesting. More than the position sensors, the pressure and barometer sensors play an important role in indoor positioning. This helps in providing reliable floor level estimates, and can have a wide range of actions – from general applications to emergency response effectiveness.


Beacons, however inexpensive and useful they might be, remain static detectors. To make the entire process more dynamic, the need of the hour is to develop software based GPS sensors, which would aid the indoor static sensors to clearly gauge the indoor positions of an individual.


So finally, we can narrow down on the various technologies involved from the sensor front. The techniques for sensing will mainly involve beacon based solutions, but the wireless communication protocols differ according to the applications.


(Image Source: Google Developers)

These three technologies play a vital role as far as fused locations and geofencing are concerned, and they are also significant in terms of indoor positioning. They facilitate a smooth transition from outdoors to indoors, and various algorithms assign confidence rankings to all the various signals in order to determine which signal to employ and how to continually refine the position readings.

However, the biggest tradeoffs in this regard would be the limitation of the network coverage as far as GPS and cellular ranges are concerned.


By strategically placing WiFi transceivers within an establishment, the user’s location can be gauged. Fingerprinting is a unique addition in this regard, and it involves smartphones switching on the WiFi for a few seconds to get the WiFi fingerprint and associate it with a specific location. Again, much like the modus involved in beacon sensing, it involves taking a reference framework to a database of known fingerprints. This is actually pretty handy and useful, and is employed by applications such as Foursquare.


Coming to the most popular solution of them all, Bluetooth Low Energy beacons are placed at strategic locations within an establishment. Their purpose is to transmit a unique signal which could be received by a smartphone. Think of it as echolocation, and based on the received signal strength picked up from a phone, the BLE beacons can assess the user’s location through triangulation methods.

However, the biggest tradeoff in this regard would be the accuracy, which arises mainly because of the coverage area within narrow spaces such as aisles.


We are already seeing Near Field Communication systems in wireless payment terminals, and with the popularisation of Android Pay and Apple Pay, NFC can only get bigger. Short range data transmission through this protocol could actually prove useful to gauge users’ locations.


Light can also play a unique role in gauging users’ locations. A company called ByteLight sends flickering light patterns through LED fixtures, which are received by the smartphone’s camera. The phone reads the code received and sends it to a server, which further understands which ‘light’ the user is under.

Besides the above methods, also worthy of mention are SLAM automatic fingerprinting systems, motion sensing, visual sensing using the phone’s camera and ultrasonic sensing.


Sensors are at the helm of affairs when it comes to indoor positioning, and these technologies are being utilised to the fullest by quite a few corporations! Indoor positioning definitely paves the path for a more robust, flexible and unique manner of gauging consumer interest and marketing!

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  • Tickto

    Great information.