How It Works

Frequently Asked Questions

What is version 2.0 of XPS (hybrid positioning system)?

Version 2.0 of XPS is a location-determination technology that uses raw location data from GPS, Cellular tower triangulation (Cell ID) and nearby Wi-Fi (802.11) access points to calculate the location of mobile devices, such as laptops, PDAs, and dual-mode phones. That location is then used by devices, applications, and services to deliver a wide-range of location-based services, including local search, advertising, friend finders, navigation, and asset tracking and recovery. For application developers, the SDK of XPS 2.0 will be available in the 4th quarter of 2008.

What is a "location-determination technology"?

A location-determination technology is a system that uses the known position of reference points and satellite signals to determine the location of mobile devices. As reference points, XPS uses Wi-Fi routers and Cellular base-stations (Cell ID), each of which broadcasts a signal that includes a unique identifier. When a device is in range of any of these reference points, Skyhook's system matches the signal data and unique identifiers to those in its database and also incorporates GPS satellite signals to determine the user's location.

Why is a "hybrid" positioning system important?

All underlying location technologies work well in varying environments and on different devices. Version 2.0 of XPS combines the relative strengths of GPS, cell tower triangulation and Skyhook's industry-leading Wi-Fi Positioning System (WPS) to determine the user's location quickly, accurately and reliably.

How is version 1.0 of XPS different than version 2.0?

Version 1.0 of XPS was a "mixed-mode" hybrid positioning system. This means that each location source (GPS, WPS or Cell tower) would provide a location estimate, and Skyhook's XPS would determine the most accurate of those estimates.

Version 2.0 of XPS is a significant improvement over "mixed-mode" hybrid systems. The raw data from each location source is considered as input, and a single location estimate is calculated. This results in a more accurate location estimate and better availability of the location system. It also opens up the possibility for reducing device power consumption by choosing to enable/disable the different location sources (based on the desired position accuracy).

Is version 2.0 of XPS like GPS?

Version 2.0 of XPS uses GPS to improve its location accuracy and performance.

Does version 2.0 of XPS replace Skyhook's Wi-Fi Positioning System (WPS)?

XPS is Skyhook's next generation location-platform. It fully leverages Skyhook's innovative and market-leading Wi-Fi Positioning System, but also incorporates GPS and cell tower triangulation to further improve accuracy, speed and reliability.

What kind of signal does a Wi-Fi access point broadcast?

When a wireless access point is powered on, it broadcasts what is basically a "Here I am!" signal every 100 milliseconds. That signal contains data about the identity, type of security (if any), and signal strength that are unique to that access point at that place and time. These data elements are required by the 802.11 standard that allows Wi-Fi access points and mobile Wi-Fi devices to communicate.

This signal falls into an "unlicensed" portion of the electromagnetic spectrum, meaning that any device that meets general specifications, may use it without having to be licensed by the Federal Communications Commission (FCC).

How does version 2.0 of XPS identify Wi-Fi access points?

Each access point has a unique Media Access Control (MAC) address which serves as a serial number for that piece of hardware, such as 00-08-74-4C-7F-1D. It broadcasts every 100 milliseconds. XPS uses this MAC address to identify individual routers.

Does version 2.0 of XPS use any other data from a Wi-Fi access point?

The other data element we use to determine location is the Received Signal Strength Indicator (RSSI), a measurement of the strength of the access point's signal at the time it is received by the mobile device. XPS uses the RSSI data to help determine how close a mobile device is to a router when it requests a location calculation and whether it is operating indoors or outdoors.

How many Wi-Fi access points are collected?

Skyhook's reference database contains tens of millions of access points. The coverage area includes tens of thousands of cities and towns across North America, Europe, and Asia.

How do you determine the location of these Wi-Fi access points?

Skyhook deploys vehicle-based signal scanning and data collection technologies, a common practice in the digital mapping and data collection industries. These Skyhook-equipped vehicles conduct systematic and comprehensive signal surveys by traveling every public road and highway in targeted coverage areas. These signal surveys capture the data output of individual access points and pair them with a date, time, and location stamp at the point where they are received by the data collection device. The data collection device captures signal readings every second, for a total of several dozen signal readings for each access point.

This survey method does not actually determine the location of a specific access point but instead creates a "fingerprint" of the signal "cloud" that is generated by that access point. By pairing the signal readings with a geographic location, WPS can then use that unique signal fingerprint - and not the actual location of an access point itself - as the reference point in calculating location.

How does this all work together so that version 2.0 of XPS is able to accurately determine location?

When a device, application, or service requests its location, in less than two seconds XPS:

  1. Scans the area to collect data on nearby Wi-Fi access points
  2. Connects to one or more GPS satellites
  3. Identifies nearby cellular towers
  4. Feeds all of this information to advanced hybrid positioning algorithms to determine location
Does version 2.0 of XPS connect to a Wi-Fi access point to collect data or calculate location?

No. At no point during the process does XPS connect to a Wi-Fi access point. The entire system operates in "receive-only" mode and uses only the data that is broadcast by the access point. This is true both while we conduct our geographic signal surveys and when XPS is integrated with a device, application, or service and calculating a location.

Are you "stealing" a Wi-Fi access point signal to use it to determine location?

No. Every access point generates a publicly available signal that can be "heard" by any Wi-Fi-enabled device within range. Skyhook has only aggregated this signal data and paired it with other information so that it can use it as reference point infrastructure to determine the location of mobile devices.

A rough analogy would be a location-determination system that uses porch lights as reference points. With a reference database about which lights were on or off and the strength and pattern of the light each lamp casts, a photosensitive device could arguably use the unique patterns it "sees" at a specific time and place, compare it with previously collected data about these porch lights, and determine its location.

Does Skyhook sell, distribute, make available or otherwise publicly disclose the access point data that you collect?

No. Skyhook is solely focused on developing location-determination technologies using Wi-Fi as our underlying reference point infrastructure. In developing this system, we have invested a significant amount of time and money to develop this reference data repository, which is now one of our core intellectual property assets.

Just as important, the data on its own - without our positioning algorithms and technology - has little value. The data we collect and how we use it is unique to the XPS system and for the purpose of calculating location.