Is Satellite Navigation Free?

  Wilham 21:17 21 Oct 2004

A month or so back I bought an electric bike on Ebay and the price included delivery. I rang the seller and gave my address, and was surprised no directions were needed to find me. He explained he had the latest computer satellite navigator, would take him to my front door. This is indeed what happened.

Two weeks ago our local press reported the late arrival of an ambulance that lost its way on an emergency call to a house. It added in the news that more public money was to be spent on sign-posts.
That is reasonable, but I ask why emergency services like fire and ambulance are not fitted with with satellite navigation?

I suppose the quick answer is cost. But do car owners who use sat nav'n pay anything toward the cost of the orbiting satellites? Do the makers of sat receivers need licences? Is it 'for free'?

Am I alone thinking the outlay must be almost trivial compared with the capital cost of a modern ambulance or fire-engine?

Or is this electronic navigation gadget over hyped?

  spuds 21:44 21 Oct 2004

Satellite Navigation services are not free, there are usually monthly/annual charges similar to the ones that your ISP charges.Plus of course, the cost of installation and all the equipment required.The cost was very high at the beginning, but the more people who subscribe will help to reduce the price, eventually it will be in reach for everyone who needs it.

The fire,ambulance,police services, even taxis and private hire cars plus courier companies and many more are moving into the realms of satellite navigation bigtime.Nothing more soothing than listening to a nice voice saying "next left half a mile ahead" or something very similar.

  TomJerry 21:48 21 Oct 2004

A simple receiver cost £300 plus. No need to pay for satellitte signal which is paied for by american tax money.

Global Navigation System was developed by US Military, but later forced by congress to open to public and also international community.

Still want to learn more including pricinple etc?

  accord 22:13 21 Oct 2004

To use sat nav is a one off payment. For example, buy a tomtom GO for approx £420, attach to the windscreen of your car by suction mount and away you go. no further payments required.

I was in a taxi the other night in Milton Keynes and the driver had one in the car. certainly looks the biz.

To answer your question Wilham, yes indeed, why dont the emergency services have such a device in there vehicles, or perhaps they do, i havent been in a fire engine since i was a wee nipper when one visited my junior school fete about 25 years ago.

  Wilham 22:43 21 Oct 2004

Yes please, I'd like to know more. Spuds is right but if just the Americans pay that way for the satellites I can see that TomJerry and accord have a point that it's free in UK. From offers in Ebay I see Sat Nav equipment has come down a lot in price. What and where at the present is the best buy?

If it's an open system, could we see complete sat nav outfits under £100 or even £50 within a year?

  accord 22:47 21 Oct 2004

click here for tomtom GO. Theres loads of sites for this. or click here for tomtoms official website.

  accord 22:50 21 Oct 2004

or......... if you have an ipaq or other pda you can use the tomtom bluetooth sat nav system. This market is huge at the moment with sat nav being a buzz word where pdas are concerned.

(Other sat nav systems are available and i have no alliance towards tomtom)

  Wilham 23:06 21 Oct 2004

accord, thanks for that. I've looked at a few comments on sat nav and there is praise for TomTom, others say you don't get minor roads on standard TomTom, you pay extra and it's not so good off the beaten path.

I suppose it's like asking what is the best buy PC?

  Belatucadrus 23:45 21 Oct 2004

You'll also need to keep it up to date, because while the Sat Nav location may be spot on, the road network changes and if the units database isn't updated you can find the it is blissfully unaware of the new bypass or ring road and occasionaly may direct you the wrong way down one way streets, after the town planners have swapped things around.

  TomJerry 00:09 22 Oct 2004

GPS: Global Positing System

GPS is funded by and controlled by the U. S. Department of Defense (DOD). While there are many thousands of civil users of GPS world-wide, the system was designed for and is operated by the U. S. military.

GPS provides specially coded satellite signals that can be processed in a GPS receiver, enabling the receiver to compute position, velocity and time.

Four GPS satellite signals are used to compute positions in three dimensions and the time offset in the receiver clock.

The nominal GPS Operational Constellation consists of 24 satellites that orbit the earth in 12 hours. There are often more than 24 operational satellites as new ones are launched to replace older satellites. The satellite orbits repeat almost the same ground track (as the earth turns beneath them) once each day. The orbit altitude is such that the satellites repeat the same track and configuration over any point approximately each 24 hours (4 minutes earlier each day). There are six orbital planes (with nominally four SVs in each), equally spaced (60 degrees apart), and inclined at about fifty-five degrees with respect to the equatorial plane. This constellation provides the user with between five and eight SVs visible from any point on the earth.

The Master Control facility is located at Schriever Air Force Base (formerly Falcon AFB) in Colorado. These monitor stations measure signals from the SVs which are incorporated into orbital models for each satellites. The models compute precise orbital data (ephemeris) and SV clock corrections for each satellite. The Master Control station uploads ephemeris and clock data to the SVs. The SVs then send subsets of the orbital ephemeris data to GPS receivers over radio signals.

The GPS User Segment consists of the GPS receivers and the user community. GPS receivers convert SV signals into position, velocity, and time estimates. Four satellites are required to compute the four dimensions of X, Y, Z (position) and Time. GPS receivers are used for navigation, positioning, time dissemination, and other research.

  Migwell 09:03 22 Oct 2004

Wow is that in simple terms.

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