I still remember my first year at college. Our faculty building wasn’t huge but it had three floors and millions of small offices placed all over its labyrinth-like floors. Navigating each floor was a headache in most cases. Biggest classrooms where easy to find but smaller offices, where various experiments and small group practical lessons took place, would always be placed in fringe areas of each floor and finding those was a mission impossible. How I wish we had indoor maps back then. My first semester would have been a breeze if we had an indoor plan of the building with every room marked and with the ability for indoor navigation.

While back in 2009 indoor mapping was a niche tech available for the world’s most famous indoor areas, today tens of thousands of buildings come with indoor maps and offer indoor navigation. Some of the maps can be found inside Google Maps while others come with other solutions available as mobile or web-based apps. They all have in common the fact they provide indoor navigation, making lives easy to millions of people each day. But what exactly is indoor mapping?

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What indoor mapping is?

Like outdoor mapping, indoor mapping is a technology used for charting areas and creating maps, but maps of indoor areas. They are usually based on architectural plans with additional layers based on specific buildings. Venues such as sports arenas have information such as numbered seats and sections. Shopping malls feature store layouts. Indoor maps of university buildings have numbered offices and classrooms as well as additional info such as which classes take place in which classroom or amphitheater.
These maps can be found inside your Google Maps or Apple Maps apps and are shown as soon as you enter a building in case it has its indoor map charted by Google, Apple, or the venue itself. But since the indoor mapping industry is far from being a monopoly (or, in this case, duopoly), other solutions exist and most of them are available as mobile apps since smartphones are the most common tech found today. For instance, your local mall may have stands with QR codes which, once scanned, automatically download a mobile app with the indoor map of the shopping mall. Students at some universities are informed they can download a mobile app with a detailed map of the campus along with indoor maps of each building located inside the campus. Closed-for-public indoor maps, used in enterprise space, can be used only by persons with access to them. Usually by employees or visitors with special clearance.

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Often, in the case of standalone maps used mostly by commercial venues such as shopping malls, apps come with additional features that build upon basic navigation function. These apps can offer users additional info such as sales happening in specific stores, repertoire in the mall’s cinema, menus at restaurants found in the shopping mall, and more. Indoor maps are extremely useful because most of us spend much of our time indoors. We work and study inside huge buildings; spend our vacations at massive resorts hosting hotels with hundreds of rooms; wander through shopping malls hosting dozens of stores and other venues; go to concerts and sports matches taking place inside enormous arenas and stadiums. Indoor mapping is here to make each visit a pleasant experience allowing visitors to focus on the experience instead on finding their way around. But, how does indoor navigation work?

How indoor Navigation works?

At its base level, indoor navigation is similar to the GPS navigation. It provides navigation, but in closed areas. Since GPS signals cannot reach enclosed spaces indoor mapping uses different technologies to provide precise navigation for users. And even if GPS signals worked in areas covered in roofs and sectioned by walls, they would be useless in every building that has more than one floor. GPS is great for outdoors where you have only one vertical layer. Most indoor areas, however, are much more complicated than that.

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So, instead of GPS something else had to be used in order to provide indoor navigation. And since we don’t need a super expensive, globally available, and extremely complicated navigation technology like GPS, there are lots of different solutions used for indoor navigation. While there are almost a dozen different technologies used for indoor navigation most of them use the same kind of receiver devices – smartphones. Smartphones are used because they are omnipresent and because they either support or can be used in combination with lots of different technologies we’re going to talk about here. Do note that in many cases two or more technologies are combined in order to provide better accuracy.

Bluetooth, usually Bluetooth Low Energy

Bluetooth is the most popular technology used for indoor navigation and positioning. The technology is fairly precise, cheap to use, and doesn’t require lots of power on the client-side (most modern smartphones support Bluetooth Low Energy standard that’s extremely energy efficient).

Most solutions employ Bluetooth beacons, which are small signal emitting devices. Signals are read by Bluetooth chips found in phones, allowing indoor navigation solutions to fairly accurately calculate user’s position inside a building. The more beacons are employed the more precise navigation is.

Along with proximity-based navigation, Bluetooth beacons can be used also for trilateration-based navigation (calculating position based on a device distance between multiple beacons).

Wi-Fi

Wi-Fi is also quite popular indoor navigation solution since nowadays virtually every building has lots of Wi-Fi access points. Since Wi-Fi access points have greater reach than Bluetooth beacons, proximity-based navigation isn’t as accurate. Wi-Fi is used mostly for trilateration-based navigation by employing RSSI (relative received signal strength indication) standard, which is available on Android phones.

Li-Fi

Li-Fi stands for Light-based communication. Li-FI emitters are LED lamps set to send light signals invisible for the human eye. The signal can be read by phone cameras or by dedicated Li-Fi receivers. Li-Fi emitters are used only for proximity-based navigation. They provide accurate positioning (the signal they emit can be read-only when a device is right next to the emitter) but require lots of Li-Fi lamps to provide accurate positioning.

QR Codes and NFC Tags

These two are used for proximity-based navigation. The location is calculated once a device scans a QR code or reads an NFC tag by linking the device and the location of the specific QR code/NFC tag. A cheap and easy to use indoor navigation tech that is lacking in ease of use because users have to manually scan QR codes. In the case of NFC tags, they have extremely limited reach and the fact is that lots of smartphones don’t come with NFC support.

Ultrasound navigation

Ultrasound-based indoor navigation uses existing audio devices such as speaker systems to emit ultrasounds beyond the human hearing range. Microphones built into phones can register these ultrasounds and calculate location-based either on proximity from an emitter or by using trilateration.

RFID cards

RFID cards are used mostly by companies to provide indoor navigation to employees. Active RFID cards (equipped with low energy chips and batteries) can emit a constant signal that can be read by RFID receivers, allowing smart navigation systems to provide near real-time navigation to employees. This is done server-side and feedback can be sent either through a building-wide system (via speakers) or by sending navigation data to phones tied to specific RFID cards.

Other, less popular, indoor navigation technologies

There are other indoor navigation technologies in use but they are way less popular than the ones listed above. ToF - Time of Flight sensors measure the time between the emission of the signal by an emitter and its return by a sensor and use that to calculate extremely precise location - sensors are combined with ultra-wide-band emitters to provide extremely precise indoor navigation. The lack of ToF sensors makes this technology fairly uncommon but, in the future, it should become more popular since there are more and more phones equipped with ToF sensors.

We also have a technology based on Earth's magnetic field variations based on the position of various steel objects found in buildings, such as carrying pillars. This tech can calculate a fairly accurate position. It isn’t popular because it requires standalone readers and because the magnetic field can fluctuate over time, requiring constant recalibration of readers. Internal phone sensors such as accelerometer, compass, and pedometer can also be used for calculating indoor location but they are quite inaccurate since they aren’t combined with external emitters.