Indoor positioning system
An indoor positioning system (IPS) is a solution to locate objects or people inside a building using radio waves, magnetic fields, acoustic signals, or other sensory information collected by mobile devices. There is currently no de facto standard for an IPS systems design. Nevertheless, there are several commercial systems on the market.
Instead of using satellites, IPS solutions rely on different technologies, including distance measurement to nearby anchor nodes (nodes with known positions, e.g., WiFi access points), magnetic positioning, dead reckoning. They either actively locate mobile devices and tags or provide ambient location or environmental context for devices to get sensed. The localized nature of an IPS has resulted in design fragmentation, with systems making use of various optical, radio, or even acoustic technologies.
System designs must take into account that at least three independent measurements are needed to unambiguously find a location (see trilateration). For smoothing to compensate for stochastic (unpredictable) errors there must be a sound method for reducing the error budget significantly. The system might include information from other systems to cope for physical ambiguity and to enable error compensation.
- 1 Applicability and precision
- 2 Relation to GPS
- 3 Locating and positioning
- 4 Locating and tracking
- 5 Identification and segregation
- 6 Non-radio technologies
- 7 Wireless technologies
- 8 Mathematics
- 9 New Technology
- 10 Uses
- 11 See also
- 12 External links
- 13 References
Applicability and precision
Due to the signal attenuation caused by construction materials, the satellite based Global Positioning System (GPS) loses significant power indoors affecting the required coverage for receivers by at least four satellites. In addition, the multiple reflections at surfaces cause multi-path propagation serving for uncontrollable errors. These very same effects are degrading all known solutions for indoor locating which uses electromagnetic waves from indoor transmitters to indoor receivers. A bundle of physical and mathematical methods is applied to compensate for these problems. Promising direction radiofrequency positioning error correction opened by the use of alternative sources of navigational information, such as Inertial Measurement Unit (IMU), monocular camera Simultaneous Localization and Mapping (SLAM) and WiFi SLAM. Integration of data from various navigation systems with different physical principles can increase the accuracy and robustness of the overall solution.
With detailed reading in the marketing documents and even in the specifications served by many of the IPS vendors, the interested customer will look for details on precision, reproducibility and other terms for quality of function with little success. Many vendors do not even tangle with the term accuracy
Relation to GPS
Global navigation satellite systems (GPS or GNSS) are generally not suitable to establish indoor locations, since microwaves will be attenuated and scattered by roofs, walls and other objects. However, in order to make positioning signals ubiquitous, integration between GPS and indoor positioning can be made.,
Currently, GNSS receivers are becoming more and more sensitive due to ceaseless progress in chip technology and processing power. High Sensitivity GNSS receivers are able to receive satellite signals in most indoor environments and attempts to determine the 3D position indoors have been successful. Besides increasing the sensitivity of the receivers, the technique of A-GPS is used, where the almanac and other information are transferred through a mobile phone.
However, proper coverage for the required four satellites to locate a receiver is not achieved with all current designs (2008–11) for indoor operations. Beyond, the average error budget for GNSS systems normally is much larger than the confinements, in which the locating shall be performed.
Locating and positioning
Locating and tracking
One of the methods to thrive for sufficient operational suitability is "tracking". Whether a sequence of locations determined form a trajectory from the first to the most actual location. Statistical methods then serve for smoothing the locations determined in a track resembling the physical capabilities of the object to move. This smoothing must be applied, when a target moves and also for a resident target, to compensate erratic measures. Otherwise the single resident location or even the followed trajectory would compose of an itenerant sequence of jumps.
Identification and segregation
In most applications the population of targets is larger than just one. Hence the IPS must serve a proper specific identification for each observed target and must be capable to segregate and separate the targets individually within the group. An IPS must be able to identify the entities being tracked, despite the "non-interesting" neighbors. Depending on the design, either a sensor network must know from which tag it has received information, or a locating device must be able to identify the targets directly.
Non-radio technologies can be used for positioning without using the existing wireless infrastructure. This can provide increased accuracy at the expense of costly equipment and installations.
Magnetic positioning can offer pedestrians with smartphones an indoor accuracy of 1–2 meters with 90% confidence level, without using the additional wireless infrastructure for positioning. Magnetic positioning is based on the iron inside buildings that create local variations in the Earth's magnetic field. Un-optimized compass chips inside smartphones can sense and record these magnetic variations to map indoor locations.
Pedestrian dead reckoning and other approaches for positioning of pedestrians propose an inertial measurement unit carried by the pedestrian either by measuring steps indirectly (step counting) or in a foot mounted approach, sometimes referring to maps or other additional sensors to constrain the inherent sensor drift encountered with inertial navigation. Inertial measures generally cover the differentials of motion, hence the location gets determined with integrating and thus requires integration constants to provide results.
Any wireless technology can be used for locating. Many different systems take advantage of existing wireless infrastructure for indoor positioning. There are three primary system topology options for hardware and software configuration, network-based, terminal-based, and terminal-assisted. Positioning accuracy can be increased at the expense of wireless infrastructure equipment and installations.
Wi-Fi-based positioning system (WPS)
Wi-Fi positioning system (WPS) is used where GPS is inadequate. The localization technique used for positioning with wireless access points is based on measuring the intensity of the received signal (received signal strength in English RSS) and the method of "fingerprinting". Typical parameters useful to geolocate the WiFi hotspot or wireless access point include the SSID and the MAC address of the access point. The accuracy depends on the number of positions that have been entered into the database. The possible signal fluctuations that may occur can increase errors and inaccuracies in the path of the user.
According to the Bluetooth Special Interest Group, Bluetooth is all about proximity, not about exact location. Bluetooth was not intended to offer a pinned location like GPS, however is known as a geo-fence or micro-fence solution which makes it an indoor proximity solution, not an indoor positioning solution. Micromapping and indoor mapping has been linked to Bluetooth and to the Bluetooth LE based iBeacon promoted by Apple Inc.. Large-scale indoor positioning system based on iBeacons has been implemented and applied in practice.
Choke point concepts
Simple concept of location indexing and presence reporting for tagged objects, uses known sensor identification only. This is usually the case with passive radio-frequency identification (RFID) systems, which do not report the signal strengths and various distances of single tags or of a bulk of tags and do not renew any before known location coordinates of the sensor or current location of any tags. Operability of such approaches requires some narrow passage to prevent from passing by out of range.
Instead of long range measurement, a dense network of low-range receivers may be arranged, e.g. in a grid pattern for economy, throughout the space being observed. Due to the low range, a tagged entity will be identified by only a few close, networked receivers. An identified tag must be within range of the identifying reader, allowing a rough approximation of the tag location. Advanced systems combine visual coverage with a camera grid with the wireless coverage for the rough location.
Long range sensor concepts
Most systems use a continuous physical measurement (such as angle and distance or distance only) along with the identification data in one combined signal. Reach by these sensors mostly covers an entire floor, or an aisle or just a single room. Short reach solutions get applied with a bunch of sensors and overlapping reach.
Angle of arrival
Angle of arrival (AoA) is the angle from which a signal arrives at a receiver. AoA is usually determined by measuring the time difference of arrival (TDOA) between multiple antennas in a sensor array. In other receivers, it is determined by an array of highly directional sensors—the angle can be determined by which sensor received the signal. AoA is usually used with triangulation and a known base line to find the location relative to two anchor transmitters.
Time of arrival
Time of arrival (ToA, also time of flight) is the amount of time a signal takes to propagate from transmitter to receiver. Because the signal propagation rate is constant and known (ignoring differences in mediums) the travel time of a signal can be used to directly calculate distance. Multiple measurements can be combined with trilateration and multilateration to find a location. This is the technique used by GPS. Systems which use ToA, generally require a complicated synchronization mechanism to maintain a reliable source of time for sensors (though this can be avoided in carefully designed systems by using repeaters to establish coupling).
The accuracy of the TOA based methods often suffers from massive multipath conditions in indoor localization, which is caused by the reflection and diffraction of the RF signal from objects (e.g., interior wall, doors or furniture) in the environment. However, it is possible to reduce the effect of multipath by applying temporal or spatial sparsity based techniques. 
Received signal strength indication
Received signal strength indication (RSSI) is a measurement of the power level received by sensor. Because radio waves propagate according to the inverse-square law, distance can be approximated based on the relationship between transmitted and received signal strength (the transmission strength is a constant based on the equipment being used), as long as no other errors contribute to faulty results. The inside of buildings is not free space, so accuracy is significantly impacted by reflection and absorption from walls. Non-stationary objects such as doors, furniture, and people can pose an even greater problem, as they can affect the signal strength in dynamic, unpredictable ways.
A lot of systems use enhanced Wi-Fi infrastructure to provide location information. None of these systems serves for proper operation with any infrastructure as is. Unfortunately, Wi-Fi signal strength measurements are extremely noisy, so there is ongoing research focused on making more accurate systems by using statistics to filter out the inaccurate input data. Wi-Fi Positioning Systems are sometimes used outdoors as a supplement to GPS on mobile devices, where only few erratic reflections disturb the results.
- Radio frequency identification (RFID): passive tags are very cost-effective, but do not support any metrics
- Ultrawide band (UWB): reduced interference with other devices
- Infrared (IR): previously included in most mobile devices
- Visible light communication (VLC): can use existing lighting systems
- Ultrasound: waves move very slowly, which results in much higher accuracy
Once sensor data has been collected, an IPS tries to determine the location from which the received transmission was most likely collected. The data from a single sensor is generally ambiguous and must be resolved by a series of statistical procedures to combine several sensor input streams.
One way to determine position is to match the data from the unknown location with a large set of known locations using an algorithm such as k-nearest neighbor. This technique requires a comprehensive on-site survey and will be inaccurate with any significant change in the environment (due to moving persons or moved objects).
Location will be calculated mathematically by approximating signal propagation and finding angles and / or distance. Inverse trigonometry will then be used to determine location:
Advanced systems combine more accurate physical models with statistical procedures:
- Bayesian statistical analysis (probabilistic model)
- Kalman filtering (for estimating proper value streams under noise conditions).
The new technology of indoor positioning system will be related with new parking system for the parking area . indoor Parking spaces are limited and they are not determined by market price; With limited space of land available, parking spaces become more challenging and short in supply. Once parking lots have been allocated to individual either the person uses it or not, no other person is permitted to pack on those lots. This has caused the needs for providing a better solution to address the challenges posed by the current problem. Therefore, a system should be designed to solve the problem. Various factors will be considered which includes. Administration of parking lots.Application software for the parking lots.Regulatory aspect of the parking spaces.Data base storage.Interface between application and system database.Make the parking lot become more specific. Easy control system for Parking.
- Efficient; indoor positioning system enables the parking lot to be used more effectively which solves the problem that parking lots are idle, but people without permission have no access to these parking spaces.
- Flexible; Everyone can book a parking lot in any time in the system. Compared to current system, the new system is more flexible to everyone.
- Economic; Compared to build more parking lots, designing a new system costs less and environmental friendly.
- Profitable; Current price for parking is around $0.25 dollars per hour.
- Fair; individual need to bid for a parking lot through in the new system the parking time duration is 2 hours. once the time is up, the driver should drive away
- Consideration; only 80% of the parking lot can be bid for. the other will be reserved by the permit.
The new parking system needs application software to support. That software is a simple car park management procedure, to achieve a vehicle getting in a parking space, getting out a parking space, registration, billing and other functions. The recognition of the license plates and the linkage with ticket data forms the basis for many additional functions in car parking management. In order to improving new parking system and balancing the supply and demand situation of parking in the coming period, project need to predict the demand for parking firstly. Before the parking system implementation, training is required. According to the plan, the parking system needs a designed online website. Hence, it is necessary that providing a training of the booking system to users. In addition, staff responsible for the vehicle also needs training. For example, if a vehicle is not leaving the parking space on the required time, the vehicle’s owner needs to be notified and the car will be towed away. That means the staff needs to make quick and accurate actions. There are databases needing to be pre-populated.the project can reduce time that spent looking for parking space, balance the parking competition and improve the traffic congestion caused by parking. Meanwhile, it also improves parking facilities utilization and optimizes parking management.
The major consumer benefit of indoor positioning is the expansion of location-aware mobile computing indoors. As mobile devices become ubiquitous, contextual awareness for applications has become a priority for developers. Most applications currently rely on GPS, however, and function poorly indoors. Applications benefiting from indoor location include:
- Augmented reality
- School campus
- Guided tours of museums
- Shopping mall maps.
- Store navigation 
- Warehouse 
- Airport, bus, train and subway stations maps
- Car location in big or multi-storey indoor parkings.
- Targeted advertising 
- Social networking
- Hospital 
- Emergency response and plans 
- Other public building maps
- Automatic vehicle location
- Bluetooth SMART
- Ekahau Site Survey
- Fuzzy locating system
- GSM localization
- Indoor mapping
- Indoor parking
- Magnetic positioning
- MALT: Micromapping, Advertising, Location and ID, and Transactions
- Near field communication (NFC)
- Real-time locating system (RTLS)
- Robotic mapping
- Sensor Fusion
- Simultaneous localization and mapping (SLAM)
- Skyhook Wireless
- Wi-Fi positioning system
- Kevin Curran, Eoghan Furey, Tom Lunney, Jose Santos, Derek Woods and Aiden Mc Caughey (2011) An Evaluation of Indoor Location Determination Technologies. Journal of Location Based Services Vol. 5, No. 2, pp: 61-78, June 2011, ISSN: 1748-9725, DOI:10.1080/17489725.2011.562927, Taylor & Francis
- Eoghan Furey, Kevin Curran and Paul Mc Kevitt (2012) HABITS: A Bayesian Filter Approach to Indoor Tracking and Location. International Journal of Bio-Inspired Computation (IJBIC) Vol. 4, No. 2, pp: 79-88, ISSN: 1758-0366, DOI: 10.1504/IJBIC.2012.047178, InderScience
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- Vladimir Maximov and Oleg Tabarovsky, LLC RTLS, Moscow, Russia (2013). Survey of Accuracy Improvement Approaches for Tightly Coupled ToA/IMU Personal Indoor Navigation System. Proceedings of International Conference on Indoor Positioning and Indoor Navigation, October 2013, Montbeliard, France.See publication here
- Wan Mohd Yaakob Wan Bejuri, Mohd Murtadha Mohamad and Maimunah Sapri (2011). Ubiquitous Positioning: A Taxonomy for Location Determination on Mobile Navigation System. Signal & Image Processing: An International Journal.Vol 2: No.1,pp: 24-34. See publication here
- Wan Mohd Yaakob Wan Bejuri, Mohd Murtadha Mohamad, Maimunah Sapri and Mohd Adly Rosly (2012). Ubiquitous WLAN/Camera Positioning using Inverse Intensity Chromaticity Space-based Feature Detection and Matching: A Preliminary Result. International Conference on Man-Machine Systems 2012 (ICOMMS 2012), Penang, MALAYSIA. See publication here, or click here if broken link
- Wan Mohd Yaakob Wan Bejuri, Mohd Murtadha Mohamad, Maimunah Sapri and Mohd Adly Rosly (2012). Investigation of Color Constancy for Ubiquitous Wireless LAN/Camera Positioning: An Initial Outcome. International Journal of Advancements in Computing Technology, Vol. 4, No. 7, pp. 269-280, See publication here
- Wan Mohd Yaakob Wan Bejuri, Mohd Murtadha Mohamad, Maimunah Sapri and Mohd Adly Rosly (2012). Performance Evaluation of Mobile U-Navigation based on GPS/WLAN Hybridization. Journal of Convergence Information Technology(JCIT), Vol. 7, No. 12, pp. 235-246, See publication here
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- GNSS Indoors — Fighting The Fading Inside GNSS
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- Sensor fusion and map aiding for indoor navigation
- Pedestrian localization for indoor environments
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- Lee, Yong Up; Kavehrad, Mohsen; , "Long-range indoor hybrid localization system design with visible light communications and wireless network," Photonics Society Summer Topical Meeting Series, 2012 IEEE , vol., no., pp.82-83, 9–11 July 2012 See publication here
- Indoor location is also useful in outer
- Indoor location and sports
- Using Indoor location and positioning systems to improve emergency plans
45 patents (Pluto Technologies Inc.) GPS over Wi-Fi. Issued US 8,484,381 Self-discovery & self learning location network. location tagging & sharing, e.g. GPS over Wi-Fi & location aware with scheduling events: predictive location, crowd & group based location enabling. Preexisting condition based upon prior knowledge from others.