Global Indoor Positioning
Filling the GNSS Gap
blake bullock, sensewhere
The now ubiquitous Google Maps blue dot celebrates its tenth birthday on November 28th this year. When the magical blue dot, shown in figure 1, first appeared on mobile devices in 2007 it was a big step forward in the utility of mobile mapping and wayfinding. Scrolling the map with keys to figure out where you were was suddenly a relic of the past. The blue dot automatically showed the device’s GPS position when available and a position derived from cell tower signals when GPS was not available. The accuracy improved over time, and once voice-prompted turn-by-turn navigation was launched, suddenly our devices became pocket navigators in car and on foot.
Many Android and iOS applications started leveraging mobile maps and positioning, and we saw the introduction of all sorts of useful and innovative services including local search, ride sharing, fitness tracking, friend finding, and social media location tagging. Additionally, mobile marketing became smarter and more relevant to users though context detection, enabling advertisers to deliver offers and suggestions in appropriate places at the right moments.
My grandparents collected paper maps and travel books from places they visited and destinations they wanted to visit. When they passed, I volunteered to give those maps a home, and now they fill a couple of boxes in my closet! Yet today I have all that rich content and more in my pocket. Innovations in digital mapping have made it possible to access digital road maps, satellite images, terrain models, and more, for countries the world over, from a browser and even more remarkably, from a smartphone. Recently, we have seen the introduction of rich indoor maps with 3D perspective views and photo realistic imaging for virtual reality applications, like the ones in figure 2. There are maps to help us find stores in malls, gates at airports, and even restrooms at concerts. Unfortunately, these are places where the blue dot struggles.
Over the years the positioning accuracy and availability on mobile devices improved with better GPS assistance data provided by the cellular network for faster startup and better accuracy. Support for GLONASS, BeiDou, and then Galileo satellite signals (collectively known as GNSS) further enhanced positioning performance by providing more satellite signals. This improved GNSS availability and accuracy in urban canyon areas, but unfortunately not indoors. When mobile devices are used indoors, the GNSS satellite data is typically not available due to signal blockage from concrete and steel, causing a black spot in the coverage areas. Shopping malls, airports, train stations, conference centers, hotel resorts, museums, and other large indoor spaces are vulnerable to GNSS black spots, and hence mobile mapping and location services are hindered.
Alternative methods of determining position indoors have been used. Cell tower positioning works indoors, but the accuracy is not precise enough for search, tracking, and other popular services. Using an IP address or Nielson designated market area (DMA) code is even less accurate, and at best can be used to determine what neighborhood a user is in. Fingerprinting techniques using wireless signals or magnetic signals have been shown to provide good accuracy indoors, but require extensive manual surveying work to calibrate the system in every building, so they are not practical for broad coverage. What is needed is an accurate indoor positioning system with broad coverage throughout indoor spaces.
Mobile phone positioning solutions from sensewhere offer accurate location data for mobile devices on a broad scale with coverage in virtually every visited indoor space. Through automatic crowdsourcing, the sensewhere servers estimate and refine the location of detected Wi-Fi and Bluetooth transmitters, which are then used for mobile device positioning indoors. The coverage area expands to include every indoor space where users go with no additional infrastructure to deploy or calibrate, as conceptualized in figure 3. The sensewhere mobile software development kit (SDK) can be integrated into any iOS or Android application. It then accesses the sensewhere servers to deliver latitude, longitude, and altitude information that is used to determine the venue and location within. Positioning is done whenever the user makes a location request while using the application, or periodically in background mode, with very low power consumption. The sensewhere servers also monitor geofences to trigger actions and detect store visits when desired for user services and mobile advertising attribution. As the physical world changes with new stores and new wireless transmitters, the automatic crowdsourcing provides the data needed for the system to adapt and adjust the transmitter database and keep it up to date.
With accurate indoor positioning, the search, track, find, and meet features work similarly to how users have come to expect when using outdoors. Mobile gaming can be extended inside, bringing players inside and providing meetup and sponsorship opportunities to businesses in malls and other public venues. Ride sharing applications can provide better guidance to the best venue exit for ride pickup, and mobile payment fraud can be more secure through independent location verification. Mobile marketing is more relevant and timely as brands and advertisers can monitor the stores and restaurants visited even in malls and transit terminals. Mobile advertising attribution is more accurate and valuable to advertisers seeking to optimize campaigns.
Tencent Holdings Limited has deployed sensewhere technology in their suite of mobile applications, including WeChat, QQ, and Tencent Maps. Through their large crowd of users, the system has automatically crowdsourced wireless transmitter data throughout China and neighboring countries. Now, more than one billion location requests are received daily from hundreds of millions of users as they search, share their location, and find their friends in indoor venues throughout China.
Location technology from sensewhere adds the blue dot to indoor maps using accurate positioning signals indoors, bringing rich mapping and accurate positioning together for compelling user experiences. See figure 4. The innovative crowdsourced solution uses existing wireless infrastructure and automatically grows in coverage and accuracy through normal use. At sensewhere, we continue to explore and add value to the field of GNSS positioning with the mix of our algorithms and expertise. The result is positioning to fill the GNSS gap, providing seamless location services to businesses and consumers wherever they go.