Anybody have any experience with this? Thinking of getting it put in my chevelle.

http://www.directed.com/security/viper/gps.asp

--rO

I've thought of installing something like that in my car, the only hole in the protection is if it is stolen and put in a closed trailer or garage. GPS antennas need clear access to 2 or 3 satellites to get a position. If you are parked under something that blocks a view o the sky you're kind of screwed. That said, it would be better than no protection. If someone steals it for a joyride, you're set!

I have designed several GPS antennas for military applications, which are much more complicated (and accurate) than the commercial products, but pattern coverage and blockage due to aircraft appendages is a real design criteria.

That's great info...isn't that why they use both cellular and GPS though? I would think that it's a very effective backup system. I mean...if your car gets put somewhere where it can't get GPS positioning and it can't get a cellular signal then you've just must have the worst karma in the world smile.gif

--rO

The GPS and Cell phone serve two different purposes. The GPS system has no transmit function, it receives signals from a satellite constellation and uses them to triangulate and give your location in three dimensional space, three satellites will give you location and altitude, more satellites will give you finer resolution and a more accurate position. The cell phone link transmits that data to the tracking company. You need both. If you don't have a cell connection, the location data can't be used; if the GPS isn't working, it won't have any data to send. I think if you do lose connection with the satellites, the last known position will be sent, it will be updated when the link is re-established, and if you lose cell phone connection, you at least know the last transmission, it will pick up when the connection is re-established. I think I'm talking myself into getting one of these.

I'm curious if they are using normal GPS and just sending that via cellular -- or if they are using the new cellular GPS stuff for emergencies. They only require a single satellite. Many new phones have this built in -- the data is automatically transmitted when you make a 911 call. I believe that by the end of next year, it will be required in all cell phones, but I'm not sure. My old Audiovox one has it already.

In any case, much easier to get a (slightly less accurate) position -- since it only needs to see one of the GPS birds. The rest it determines based on cellular tower data.

- John...