Inovonics Radius Administrator - Manual (Page 45)

Setting Up the Inovonics Positioning System
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11.2 Selecting a Vector Mapping Method
There are two ways of creating the vector map necessary to establish location:
the known signal pattern method, which uses fixed end devices; and the point
of interest method, used in sites without fixed end devices. Both methods rely
on location-enabled Inovonics repeaters to provide signal strength information
for monitored end devices in the Radius system.
When establishing your location system, it’s important to think about the
design needs of your particular site. For instance, when you add or move a
repeater, the algorithm changes. Though the known signal method will
recompile easily, all the RF fingerprinting necessary to establish a point of
interest vector map will need to be recreated.
One thing to remember is that adding universal transmitters to establish a
known signal pattern method can be achieved easily and inexpensively. It’s
also worth remembering that the two methods are not exclusive; both methods
can be used in tandem to achieve greater resolution.
11.2.1 The Known Signal Pattern Method
The known signal pattern method relies on the check-in messages sent by
fixed end devices to build a vector map used for determining location. Once
the system is in place, and all the location-enabled repeaters added to the
network, the system must run for eight hours to build the vector map. Once
built, the mathematical algorithm will constantly update to compensate for real
world environmental changes.
When an alarm from a mobile end device is sent, the signal strength
information from the alarm message is compared to each point on the vector
map, and location determined by finding the best comparison.
Caution: Because location works best with multiple points of interest, the known signal
pattern method will need to be augmented with the point of interest method to
work properly.
11.2.2 The Point of Interest Method
Using the point of interest method, a mobile end device is activated at different
points throughout a site and the signal strength information saved in the
Radius system, creating a map of the wireless climate that allows location to
be determined.