Principles of Operation
Hours's patented location technology provides a unique solution for ascertaining location with extreme accuracy and reliability.Most location technologies utilize calculations based on Time Difference of Arrival or on triangulation and / or trilateration of intensity measurements from RF beacons.
Horus utilizes a different approach from which it derives its benefits. Its approach utilizes a combination of pattern recognition and Bayesian statistical processing to determine the location.
The first step in the location process is the creation of a radio map of the location and reception signatures of all the RF sources relevant to the location. This is done using AlphTrek's easy to use Rover position calibration system.
RF sources such as standard wifi access points provide the radio beacons for Horus's operation. These off the shelf low cost devices may already be installed and operating in many commercial environments. If not adding the devices is low tech and low cost. The devices are best distributed around the peripheries of the area to be calibrated.
Figure 1 Rover Calibration
Calibrating Horus
The Rover calibration system is an interactive graphics's application that can be run on any standard laptop computer that is wifi enabled. A graphics rendering or CAD drawing of the area to be calibrated is provided to Rover as the location reference . The Rover operator begins calibration by moving to a location in the area to be calibrated, clicking the corresponding location on the lap top screen begins the calibration process. A few seconds later the PC will beep and indicated the point is captured. Calibration continues by repeating the step at the next calibration point. The more points the greater the accuracy.
Figure 1 shows a typical Rover layout graphic for a segment of a floor of offices. the location of the user (Rover operator) and the location of the beacons are shown for illustrative purposes. The calibrated points become visible as they are added.
Calibration isfast and easy and multiple areas may be aggregated and managed bythe Horus system.
Radio Map Image
Rover labels each point and captures a series of data intensity measurement for each one creating a signature for each calibration point. The result of a calibrated space is an array of radio intensity signatures creating a unique radio map image as shown in figure 2.
Figure 2 Horus Radio Map
The Horus radio map shows the intensity plot (color coded) of the RF signal at the calibration point.
The calibration process creates a database of radio map data which is then used to facilitated location identification by Horus enabled devices and tags.
Note: The location processing need not take place on the mobile client. The client application need only transferthe location data itsees to the server for computation.This conserves power and simplifies portations.
Location Methodology
Horus enabled devices operate by collecting RF intensity data from the access points detected by the client device (any wifi enabledcell phone PDA, MP3 player or tag) Based on the radio map image data collected at a point by the Horus client the location is ascertained. It is ascertained by matching the pattern against the database of stored radio maps and using a Bayesian statistical algorithmsfind the most likely labeledlocation.
The Horus location process is more closely related to the operation of a search engine then to the measurement techniques used in other systems.
Its use of histogram signature data derived from multiple samples and the nature of the "recognition" algorithm provides high accuracy and a great immunity from from signal noise and variations caused by real world interactions such as people, moving crowds, rearranged furniture, etc.
Horus is unique andits results are unequalled.