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Another Freakin WAAS question


Guest blackjak

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Guest blackjak

I have an Etrex Venture, and when I am getting differential data, the "d" designation appears on my sat strength bars. However, the accuracy reading does not change. (Stays at about 20 feet) Even though the accuracy reading doesn't change, am I still getting the 10' accuracy because of the diff data??

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Guest mrgigabyte

Whether WAAS at your latitude is of any use is debatable. There are no active WAAS base stations in Canada. As such, you will be receiving erroneous ionosphere correction data that is extrapolated from the nearest US stations south of Calgary.

 

In theory, yet unproven to my knowledge, you should still be able to obtain timing and orbit corrections which may provide a few metres of improvement at best. This too is debatable.

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Once outside of the ground station network there's been cases reported where accuracy has actually decreased. That is even worse than Standard Positioning Service accuracy.

 

Again when looking at what the unit's accuarcy it's still only an estimate as well as being a propriety algorithm. Then with most units the stated accuracy can be less than the coordinate base being used, which is rather mis-leading.

 

To be exactly sure of what is going on the data can be analysed against a known point. In Garmins case it's also possible to then check the actual error to the unit's estimated error.

 

Cheers, Kerry.

 

[This message has been edited by Kerry (edited 12 November 2001).]

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