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Indoor localization

Localization or positioning is a well-known service nowadays. Almost everyone uses the Global Positioning System (GPS) when driving a car or looking for the right street. GPS is so popular that in modern smartphones there are already all navigation tools built-in: the GPS receiver and the map. However, the main disadvantage of GPS is loss of signal inside buildings or underground (in tunnels and so on).

Indoor localization is an important complement and an alternative to GPS. Unlike GPS, it doesn’t provide global coverage, but can be more accurate, efficient, and adaptive to local environments such as airports, metro stations, tunnels, and other indoor areas. Wireless LAN (WLAN) and Bluetooth beacon location fingerprinting is one of the well-known approaches that are used for indoor localization, and this technology is integrated into the TASSTA system.

TASSTA location data is based on both positioning systems (GPS) and indoor localization, and they complement each other.

The GPS portion is based on signals sent by GPS satellites. The more satellites a GPS receiver can find, the better the accuracy.

In a similar way to GPS satellites, TASSTA indoor localization requires WLAN hotspots, access points and Bluetooth beacons. TASSTA indoor localization is based on location fingerprints of existing environments.

The positioning algorithm makes snapshots of both commercial WLAN hotspots, private access points and Bluetooth beacons without needing registration or access to the data network. This creates the perfect add-on to regular GPS tracking, able to provide the positioning of users in multi-story buildings, accurate within a few meters.

Role of T.Flex in indoor localization

During normal day-to-day operations as a T.Flex user, you are moving about in an environment that has already been fingerprinted and analyzed. Therefore, you don't have to do anything to get the benefits of indoor localization.

However, T.Flex is used as the main tool during the final stages of the location fingerprinting process, for collecting measurements. The following procedure and tips are included here for personnel who perform the measurement collection. If you are not tasked with indoor localization configuration, you can safely disregard this information.

Collecting measurements

Collecting measurements is an important stage in indoor localization preparations. To perform the procedure, you need one mobile device with T.Flex installed.


At this time, we recommend using T.Flex Android for the purpose, because T.Flex iOS doesn't yet have feature parity with it. In particular, indoor localization in T.Flex iOS works only with Bluetooth beacons but not Wi-Fi hotspots.

To collect measurements with T.Flex

  1. Log into T.Flex.
  2. Make sure Bluetooth and GPS are enabled on the device and accessible for the application.
  3. Go to the Indoor Localization menu.
  4. Select Training mode from the options.
  5. Select the level to collect measurements for.
  6. If necessary, select Change grid step from options (the default is 12 rows or 2 meters if the map size allows).
  7. Go to the collection point and select it on screen.
  8. Tap Start to begin collecting measurements.
  9. At least 5 measurements need to be collected before the Stop button appears. 10 to 15 measurements per point is recommended.
  10. If necessary, you can tap the Cancel button to discard collected measurements and return to point selection.
  11. Points that have saved data are green and always visible no matter the grid step. In the event of some mistake during collection, you can select a point with collected data and delete the data by selecting Discard not sent data from the options. This works only for data that has not yet been sent to the server.
  12. Repeat the collection process until all the required data has been collected.
  13. If necessary, use the Export not sent data action. It can be useful to have a copy of collected measurements. The copy will be saved locally. On iOS, the destination path can be specified. The resulting data can be sent by email or shared by other means.
    Files are split so they don't exceed 500 measurements per file.
  14. When collection finishes, tap Send to send collected measurements to server. On iOS, a counter shows the number of requests sent to the server. Points that are available on the server are blue and always visible no matter the grid step.
  15. You can add additional measurements to both green and blue points. Measurements are added, not replaced.
  16. Use the Go to location option to return from Training mode.
Notes about taking measurements:
  • If Mixed mode is configured on the server, then using Android and iOS devices in the same areas is not recommended.
  • Bluetooth sensitivity can vary from device to device, so it is recommended that you collect measurements with the same device model that will be used for regular work.
  • Collect measurements at normal height, meaning around an average person's chest height.
  • Do not change beacon settings if measurements have already been collected.
  • Special iBeacon settings that are part of the UUID are not used for indoor localization. You only need to make sure the UUID is different for each iBeacon.
  • The more evenly you distribute the signal sources, the better the resulting accuracy. Mobile devices should preferably receive good signal from at least 3 sources.
  • Avoid positioning signal sources near microwave devices.
  • If possible, position Bluetooth beacons high (attach them to the ceiling or walls) to avoid obstacles that can decrease the signal level.
  • To increase accuracy for Bluetooth beacons, signal strength may require adjustment depending on distance between the beacons to follow the previous recommendation. If you put beacons further apart, signal strength can be increased.
  • It is advised that you collect at points that are no more than 2 meters apart.
  • A minimum of 5 measurements are collected per point (this is the minimum value before collection can be stopped). Consider making 10–15 measurements.
  • For adjacent rooms separated by walls, to determine the room correctly, collect points near walls from both sides of the wall. Collecting near the wall in one adjacent room and not doing so in the other can lead to positioning in the wrong room.
  • Avoid collecting data during some non-typical situations in rooms such as turned on microwave ovens nearby, unusually high numbers of people with devices changing their position or opened doors that are normally closed.
  • If a mistake occurs during collection at a point, collection can be canceled. If the data is saved already, you can remove the collected data for the point in the options menu. If the data has already been sent to the server, it can be removed by the T.Rodon dispatcher.
  • Export options on mobile devices allow users to have a copy of collected measurements before sending them to the server. This can be useful in the event of a network issue or if the same data needs to go to multiple servers.