Always On GPS...
James Parsons contacted me to let me know about Always On GPS. This is a Pocket PC application that enables constant GPS operation even within GPS shadows where ordinarily GPS stops working, like urban canyons and indoors.
It works by constantly scanning for WiFi spots and then correlating these to GPS co-ordinates whenever GPS coverage allows.
Clearly, the effectiveness of this technique is highly dependent on the geographical coincidence of WiFi radiation with GPS coverage in the margins. A table of WiFi-GPS coincidence needs to be built. Hence, performance is going to be variable from one area to another because of the reliance upon WiFi radiation to fill the gaps, which is going to be highly location dependent.
The solution also requires training in order to build up an internal coincidence table. I don't know if the designers have thought about a networked version that enables users to share tables. Theoretically, this would improve accuracy and the training process. It would also enable users to move to new areas that would not otherwise be in their device training table.
This is an interesting variant of a hybrid location-finding system and one that circumvents mobile operator involvement. I'd love to see a WiFi coverage map for a city area in order to understand better the potential effectiveness of this approach.
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