Thread: GPSs are all wrong!

I seem to remember reading that the public GPS signal has an accuracy of, I think, 0.5 metres, while the military version is more accurate, but I could be wrong on the details.

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More technobabble...

The GPS satellite broadcasts a time signal and a thing known as an almanac, basically a file telling the receiver where the GPS satellites are going to be for the next (I think) 3 months.

The receiver reads the time signal, compares it with its own time and calculates how far away the satellite is by the difference in time. To be accurate the system needs to be reading from 4 satellites, preferably spaced across the sky.

The fourth satellite is used to calculate elevation, so if there are only 3 that can be used the GPS guesses the elevation based on the last good fix. This works on a plain, or on water, but is not much good in hilly terrain. If you are in this situation, and can download the breadcrumbs and overlay them on a map the calculated position gets less and less precise rather quickly.

When GPS first became available the US decreed that civilian units had an inbuilt error, to prevent consumer GPS being used to target weapons. The error (which was random) was from the satellite. This random error, however, was turned off by the Clinton administration.

Driving out to Longreach recently and my gps showed the rail line on the southern side of the road when it was on the northern side. Then there was a crossing which never existed and the rail changed sides.At least it was showing on the correct side.

I see a possible problem here in time to come with day light savings and it could have a large effect on global warming
DO you think some one should tell the greenies about before its toooo late.?

Hodgo

Originally Posted by hodgo

I see a possible problem here in time to come with day light savings and it could have a large effect on global warming

DO you think some one should tell the greenies about before its toooo late.?



Hodgo

What are you smoking?

won't an extra hour of daylight warm the planet up more?

Originally Posted by hodgo

I see a possible problem here in time to come with day light savings and it could have a large effect on global warming
DO you think some one should tell the greenies about before its toooo late.?

Hodgo

just change the time on your gps....it wont know.

Originally Posted by hodgo

I see a possible problem here in time to come with day light savings and it could have a large effect on global warming
DO you think some one should tell the greenies about before its toooo late.?

Hodgo

Move to Queensland. We don't do unnatural stuff like tinker with the time up here.

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