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The limitations of GPS and A-GPS

GPS signals were designed for accurate tracking and location in open outdoor areas; however, indoors and in urban areas, the technology is not reliable. Assisted GPS (A-GPS) helps the GPS receiver by providing an alternate source of the fragile navigation message and helping the receiver average for extended periods of time.  However,  even A-GPS is unreliable indoors due to the fundamental physics of GPS satellite signals.

 

Rosum's TV Advantage

In contrast, television signals were designed for indoor reception. Rosum TV-GPS uses commercial broadcast TV signals to provide reliable positioning indoors and in urban environments. By combining TV signals with GPS signals, Rosum can provide seamless indoor/outdoor coverage across all environments.

 

Rosum's TV-GPS

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Everything said on the link provided is true concerning the physics behind the concept.

 

The stronger signal (1000 W vs. 500 W), the lower frequency (longer wavelength), and the wider bandwidth (wider wave) are all definitely more conducive to triangulating a position inside a building than traditional GPS.

 

It may have its uses.

 

Edit: Please disregard the fact thaty I can't spell condusive. :unsure:

Edited by tabulator32
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I note that Trimble is one of their technology partners and they certainly know the technical details of GPS and any pitfalls that would be likely with this TV/GPS hybrid.

 

The basic table presented in the link is correct on the signal characteristics, but I'd still be concerned on a few issues. First is that elevation wouldn't be measured by this method since the TV transmitting towers are all going to be in roughly the same horizontal plane - unlike GPS where the satellites appear at various heights in the sky. One way around that would be to have the Location Server monitor the current barometric pressure and use data from a pressure sensor in the user's device to determine the elevation. A second issue is multipath. While the lower frequency of TV signals lets it penetrate buildings better, there could be problems with reflected signals being as strong, or even stronger than the direct signal. That would lead to an incorrect pseudo-range and decreased accuracy. The third issue is that the user's device is no longer stand-alone like it is with GPS. It requires a digital data communication with the Location Server, probably over a cellular phone connection. So there could be subscription charges and some issues with coverage areas - you need to be in a location where you get several good TV signals plus cellular reception.

 

Deneye asked about DGPS. It's alive and well, in fact WAAS is one form of DGPS and has reduced the need for the more traditional DGPS with a separate beacon receiver in many applications. But DGPS still requires that you have good reception of at least 3 and preferably more GPS satellite signals. It improves your accuracy under those conditions, but doesn't help inside many buildings where the GPS signals don't get through.

Edited by peter
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Reliable? Maybe.

Convenient? Maybe not.

 

gps-antenna.jpg

But don't you worry. We know how these things work. In a couple of years they will have the antenna size cut down to half of its current version. Then you will see the general public really jump on this. It is the people out here on the bleeding edge of technology that will drive the market.

 

:unsure:

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Uhhh sure :unsure: I think the way geocaching is set up right now, most GPS's work fine! :laughing:

Treecover?

 

I get a lot more excercise when looking for a cache under tree cover. It's weird when you walk 500 ft and your GPSr says you have gone 20. :laughing: This TV thing should work well for that.

 

Luna

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Is my iFinder Cable-Ready?

 

I think this is a great concept if you lose your keys. Just waypoint them when you get home, then fire up the GPSr when you're getting ready for work.

 

Perhaps this is how they found the Hispanic mugger on Law & Order last Sunday night when they were Geo-couching.

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