#PositioningTechnology

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China Made GPS vs AGPS vs WiFi Positioning Accuracy

There are Three major positioning technologies. A phone can figure out its location in several ways: by using Personal GPS Tracking Devices, Assisted GPS or Wi-Fi positioning. GPS connects to satellites orbiting the Earth, and figures out where it is compared to the satellites. Most GPS-enabled cell phones, including the 3G iPhone, employ a technology known as Assisted GPS (A-GPS). With A-GPS many of the functions of a full GPS receiver are performed by a remote GPS location server. Wi-Fi positioning depends on companies like Skyhook, who record the locations of Wi-Fi networks. Your phone can then look at nearby Wi-Fi networks and figure out where it is. Android smartphones and iPhones can use GPS, cell tower triangulation and nearby Wi-Fi networks to get a precise fix. On the other hand, iPods can only use Wi-Fi positioning.

GPS Positioning Positioning system can be categorized depending on the target environment as either indoor, outdoor, or mixed type. For localization in an outdoor environment, global navigation satellite systems (GNSS) such as GPS have been used in a wide range of applications including tracking and asset management systems; transport navigation and guidance; synchronization of telecommunications networks; geodetic survey. GPS works extremely well in outdoor positioning. Unfortunately,

China Made GPS

does not perform well in urban canyons, close to walls, buildings, trees, indoors, and in underground environments as the signal from the GPS satellites is too weak to come across most buildings thus making GPS ineffective for indoor localization.

GPS  Positioning

Assisted GPS (AGPS) is an intricate system designed to provide indoor and outdoor positioning by capitalizing on several low cost sensors. AGPS is primarily utilized in low cost navigation devices such as cell phones and car navigation systems. The sensors typically utilized in AGPS include, cell towers, GPS, map matching, WiFi, Bluetooth and RFID. The accuracy of these systems range from meter level with GPS for outdoor positioning and RFID tags for in door positioning, to cell towers, with an accuracy ranging from 200 m to 5 km. While it is possible to utilize services such as WiFi, Bluetooth and RFID in and outdoor environment, they are an additional cost to the service provider and is typical for these services to only be utilized in environments where GPS is unavailable or unreliable. The figure on the right compares the accuracy level of the different techniques and its applicability for indoor and outdoor positioning. The focus of this blog post will be positioning accuracy of AGPS using the outdoor techniques.

WiFi positioning

WiFi positioning uses terrestrial based WiFi access points (APs) to determine location. Over the past several years tens of millions of APs using the 802.11 standard have been deployed by individuals, homeowners, businesses, academic institutions, retail stores and public buildings. All of these APs repeatedly broadcast a signal announcing their existence to the surrounding area. These signals typically travel several hundred meters in all directions. The density of APs in urban areas is so high that the signals often overlap, creating a natural reference system for determining location. WiFi positioning software identifies the existing WiFi signals within range of a WiFi enabled mobile device and calculates the current location of the device. Positional errors in WiFi also reveal erratic spatial patterns resulting from the design of the calibration effort underlying the WiFi positioning system. Cellular positioning using the 3G iPhone is the least accurate positioning method (median error of 600 m for 64 observations), consistent with previous studies. Pros and cons of the three positioningtechnologies are presented in terms of coverage, accuracy and reliability, followed by a discussion of the implications for LBS using the 3G iPhone and similar mobile devices.

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http://www.iconcox.com/