Indoor Location Services
Wide adoption of smartphones has enabled people to use location services and learn more about the world around them. As usage of location services has increased, so has the desire to improve the accuracy and precision of their determined position on a map.
GPS is traditionally used outdoors and enables accuracy within 3 meters; however, GPS cannot be used reliably, if at all, inside of buildings. Signals become degraded and location cannot be accurately determined. This limits the reach of location services to only outdoor application.
Below we will look at a few emerging technologies and how they are used to overcome the challenges surrounding indoor location services.
Introduction
Since GPS and cell tower triangulation were introduced to smartphones in the mid 2000s, three-quarters of all smartphone users regularly take advantage of their current location to get information or directions relevant to the world around them.
This functionality enables interacting with your environment possible on a large scale. However, when people want to interact through their mobile devices with surroundings on a much smaller scale, i.e. further information about a painting in a front of them at a museum, GPS and cell tower triangulation cannot provide precise enough location.
Utilizing WiFi signals, iBeacons and sensors built into mobile devices, new offerings have hit the market capable of providing highly accurate indoor positioning. The ability to bring the coveted experience of context-aware applications indoors creates many opportunities in retail, tourism, and healthcare, among others.
Context-aware applications provide services that are relevant and appropriate to a particular person, place and time. With minimal effort, interaction with surroundings becomes seamless. This nearly invisible computation has become a given with many applications we use everyday.
To bring this same context-awareness to a hyper-local level, technologies beyond GPS and cell-tower triangulation need to be considered. Hardware already common on most smartphones has been, in a sense, repurposed to provide higher accuracy for positioning. Below are some of the common hardware components and sensors accessed to augment traditional location services.
Sensors and Hardware Used for Indoor Location
Hardware
-WiFi Antenna
-Bluetooth
-GPS
Sensors
-Magnetomer
-Accelerometer
-Altimeter*
-Pedometer*
*Visual sensor: information is derived from other hardware sensors
WiFi Location Services
The most common enabler of indoor location positioning is WiFi signals. Using the measured intensity of received signal strength from a wireless access point, distance can be calculated based on a calibrated value. A minimum of three access points must be in range to determine a single location.
With just one access point, the devices location could theoretically be on any point on a circumference where radius is equal to a calculated distance based on signal strength. With two access points, a devices location could be one of two spots: the intersections of the circumferences of two access points. When three access points are in range, there is only one possible location; the intersection of three circumferences as illustrated in the diagram below.
This process of calculating position using geometrical measurements of circles and triangles is known as trilateration.
WiFi based location also uses fingerprinting to aid with location accuracy. Fingerprinting is the process of collecting location and associating it with nearby access points SSID and MAC addresses. This location information is stored anonymously in a database by companies like Apple and Google and then used to improve location retrieval and accuracy for others in the future. This is why phones prompt you to turn on WiFi to improve location accuracy.
With multiple fingerprinted access points inside of a building, trilateration can be used to determine a position within 2.5 meters of accuracy. This is comparable to the accuracy of GPS systems when used outdoors.
iBeacons
iBeacons can either be used to complement or in place of WiFi access points for trilateration. Similar to WiFi positioning, iBeacons estimate distance based on received signal strength from Bluetooth Low Energy signals emitted by iBeacons. iBeacons are golf ball-sized, battery powered devices which constantly broadcast their presence. If three or more iBeacons are in range and have a known location, position can be determined.
Setting up a wide array of iBeacons at your location has some benefits in comparison to a WiFi location framework. iBeacons are cheap ($50), secure, simple and easy to tune ( i.e. signal strength). However, iBeacons are better used for proximity and notifications rather than location. If using iBeacons solely for location, they should have their broadcasting power set to maximum so that as many iBeacons are visible as possible. This drain on battery is one of the reasons iBeacons are better used in combination with WiFi networks. Also, users must have downloaded an application and enabled Bluetooth before they can begin locating and receiving notifications.
Communication with iBeacon devices is only compatible on iPhone 4S / iPad 3 and upwards running iOS 7+ (over 75% of iPhones in use) as well as Android devices running version 4.3 and upwards (almost 25% of devices in use). Fluctuations in signals are generally greater on Android devices. This can be attributed to Apple’s Core Location framework using noise reduction methods for Bluetooth LE signals.
Magnetometer
The magnetometer is a sensor included in most mobile devices that is commonly used as a digital compass on the device. One company in particular has reimagined the magnetometers purpose. Instead of using the sensor to find North, it is used to detect magnetic disturbances indoors.
Buildings constructed with steel beams, wall studs, and other materials emit a magnetic field which is detected by the magnetometer. These fields are mapped and associated with points on a map to enable indoor location services without any additional setup. A user doesn’t need to enable WiFi or Bluetooth to use this type of system.
New with iOS 8
With the announcement of iOS 8, Apple introduced their own indoor location service built into the operating system. Utilizing the M7 motion chip and WiFi / iBeacon technology, iPhone 5s and greater can recognize when a user is indoors and begin detecting location. The operating system also shuts down Cell and GPS tracking when indoors for battery savings. This technology will initially be used in public places where Apple is able to map in collaboration with building owners.
Conclusion
Choosing the correct indoor location technology requires understanding of the existing infrastructure in your building as well as the business need.
Enabling real-time indoor location services can be solved with a variety of new technologies and techniques. However, choosing the correct indoor location technology requires understanding of the existing infrastructure in your building as well as the business need. The uses are nearly endless and will bring a new level of context aware apps to mobile devices already in the hands of millions of users. BlueFletch can assist with a site analysis and use case review should your company want to invest in indoor location services.
