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Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Mon Feb 12, 2007 5:46 am Post subject: Kitfox-List:

 	  Quote: 	
		   From: Noel Loveys [noelloveys(at)yahoo.ca] 

 The further you deviate from the equator the worse it gets. 


	


Wow, how does it work, Noel? Because I've never heard that before. The way I understand it is that:

1) Because of the angles made by the satellites (imagine them in perspective over the earth) the altitude has less accuracy than the latitude and longitude.

2) The earth surface reference a.k.a. mean sea level, is very uneven over the globe. Much like Lynn's magnetic abnormalies, the earth is uneven in density and shape. The GPS system calculates first a position to a "perfect" place, then adjust it for the local "geoidal height."

But that worldwide table has a resolution of maybe ten square miles and that may not be good enough for some place. It's just a question place on the instrument's memory.



And I don't think it has something to do with your present latitude.



Regarding Loran C, its accuracy is far from being that of the GPS. It is based, like the British Decca system, on time difference between a master and slave stations. I am not sure how it could measure altitude, though. And Locan C coverage is only limited to North America and some places of interest for NATO like north Norway.



Incidentally, 25 years ago, the company I worked for was selling a lot of Loran C simulators to maritime colleges.



Cheers,

Michel

do not archive

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_________________
Kitfox 3 - Jabiru 2200

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Feb 12, 2007 6:34 pm Post subject: Kitfox-List:

I live close enough to a Loran C station that I used to get a consistent

clicking in the phone here.  I still hear the Loran C signal on AM radio

when passing under the power lines at the end of my driveway.  Han

operations on 160 meters is a definite no no after dark.



Three years ago the Electronics technician ( one of them at least) at the

station was a close friend.  I got several, let's just say more than the

class A tours of the facility.  The technology at the transmitting stations

is fantastic.  They have scopes there which show the location of the other

stations in the chain and you can actually graphically see whether your

signal is in the right place in time or not.  You can also see the position

of all the other stations in the chain.  About two hundred miles form here

there is a station that is part of two chains, the Mid-Atlantic and the

North Atlantic chains their station must be completely mind blowing!  For t

tecchie any way.   The North Atlantic Chain is very accurate far beyond the

capabilities of the old English Decca system.  How they were going to

incorporate altitude capabilities into the loran C signal I have no idea.  I

was told it was an add on to the present chains and it would require updated

receivers.



The local station has two or three atomic clocks on sight.  They operate

completely independently of the other clocks in the chain.  If I remember

correctly, and it's been three years, the acceptable range of clock accuracy

is something like 40 picoseconds.  The local station tried to maintain three

picoseconds accuracy.  If the other stations in the chain were doing the

same thing it will translate to an accuracy something like of ten feet any

where in the North Atlantic area.  I can't even say if receivers have that

kind of resolution.  I never thought to ask if they could track continental

drift.



Noel



[quote] --

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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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