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  #41  
Old August 27th 04, 04:28 AM
John McWilliams
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Mxsmanic wrote:

John McWilliams writes:


... which in the case of at least Macs running osX, themselves auto-synch to
atomic clocks.



Macs are furnished with atomic clocks?

No, that's extra and it's bluetooth.

Most of us, tho, prefer the server method, being rather cheaper.

--
John McWilliams
  #42  
Old August 27th 04, 04:28 AM
John McWilliams
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Mxsmanic wrote:

John McWilliams writes:


... which in the case of at least Macs running osX, themselves auto-synch to
atomic clocks.



Macs are furnished with atomic clocks?

No, that's extra and it's bluetooth.

Most of us, tho, prefer the server method, being rather cheaper.

--
John McWilliams
  #43  
Old August 27th 04, 04:33 AM
John McWilliams
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Rodney Myrvaagnes wrote:

On Thu, 26 Aug 2004 17:47:12 GMT, "Arty Facting"
wrote:


Hi

I don't know if you know so I'll mention it anyway

Most GPS units have a measurement accuracy or inaccuracy.

It would be fine if it was consistent day-in & day-out, but it is not

It varies with signal and satellite availability and also with weather
conditions.

The reason I mention this is because you may return to bang the same co-ords
as on the GPS and be up to 30 yards from what you wanted to find. That
being said & writ GPS units are mega-phun!


Before WAAS and while selective availability was in effect, it could
wander as far as 400 feet. However, in recent years I have found about
2 meters to be the practical limit. I check when tied up in the marina
slip occasionally.

There is no way you could come back to the wrong gravestone in an
ordinary cemetary.


The change was made several years ago, and was widely discussed in those
places that discuss such things.

A few feet variation, and not even employing a local point. With one of
those, you can find the same entrance to an anthill...

--
John Mcwilliams
  #44  
Old August 27th 04, 04:33 AM
John McWilliams
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Posts: n/a
Default

Rodney Myrvaagnes wrote:

On Thu, 26 Aug 2004 17:47:12 GMT, "Arty Facting"
wrote:


Hi

I don't know if you know so I'll mention it anyway

Most GPS units have a measurement accuracy or inaccuracy.

It would be fine if it was consistent day-in & day-out, but it is not

It varies with signal and satellite availability and also with weather
conditions.

The reason I mention this is because you may return to bang the same co-ords
as on the GPS and be up to 30 yards from what you wanted to find. That
being said & writ GPS units are mega-phun!


Before WAAS and while selective availability was in effect, it could
wander as far as 400 feet. However, in recent years I have found about
2 meters to be the practical limit. I check when tied up in the marina
slip occasionally.

There is no way you could come back to the wrong gravestone in an
ordinary cemetary.


The change was made several years ago, and was widely discussed in those
places that discuss such things.

A few feet variation, and not even employing a local point. With one of
those, you can find the same entrance to an anthill...

--
John Mcwilliams
  #45  
Old August 27th 04, 05:20 AM
Rodney Myrvaagnes
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Default

On Thu, 26 Aug 2004 23:21:15 GMT, "Arty Facting"
wrote:

There is an interesting test that can be done with some units to visualise
variabilities

The test is even better if an alternative power supply is rigged to the unit

leave the unit in one spot - don't move it, not even an inch. Then let it
run for as long as you can. A couple of hours or even overnight

Then look at the track it has traced

Ideally all the points should cluster around a single co-ord

Chances are there will be a fair bit of movement as seen in the tracks
recorded and displayed and this, remember, is for a stationary unit

I mention this merely to retain some sense of rationality and
proportionality as I have met people that are under the impression that
there are no such things as error bounds.


Indeed. All my statements are based on measurements. Before SA was
turned off, several university web sites kept continuous plots of the
wandering. Now you can do it with the internal plot on just about any
GPS.
Artio
(formerly das Bagal or even Bagal)

"Rodney Myrvaagnes" wrote in message
.. .
On Thu, 26 Aug 2004 17:47:12 GMT, "Arty Facting"
wrote:

Hi

I don't know if you know so I'll mention it anyway

Most GPS units have a measurement accuracy or inaccuracy.

It would be fine if it was consistent day-in & day-out, but it is not

It varies with signal and satellite availability and also with weather
conditions.

The reason I mention this is because you may return to bang the same

co-ords
as on the GPS and be up to 30 yards from what you wanted to find. That
being said & writ GPS units are mega-phun!

Before WAAS and while selective availability was in effect, it could
wander as far as 400 feet. However, in recent years I have found about
2 meters to be the practical limit. I check when tied up in the marina
slip occasionally.

There is no way you could come back to the wrong gravestone in an
ordinary cemetary.


Rodney Myrvaagnes NYC


We have achieved faith-based science,
faith-based economics, faith-based law
enforcement, and faith-based missile
defense.
What's next? Faith-based air traffic control?



Rodney Myrvaagnes NYC


We have achieved faith-based science,
faith-based economics, faith-based law
enforcement, and faith-based missile
defense.
What's next? Faith-based air traffic control?
  #46  
Old August 27th 04, 05:20 AM
Rodney Myrvaagnes
external usenet poster
 
Posts: n/a
Default

On Thu, 26 Aug 2004 23:21:15 GMT, "Arty Facting"
wrote:

There is an interesting test that can be done with some units to visualise
variabilities

The test is even better if an alternative power supply is rigged to the unit

leave the unit in one spot - don't move it, not even an inch. Then let it
run for as long as you can. A couple of hours or even overnight

Then look at the track it has traced

Ideally all the points should cluster around a single co-ord

Chances are there will be a fair bit of movement as seen in the tracks
recorded and displayed and this, remember, is for a stationary unit

I mention this merely to retain some sense of rationality and
proportionality as I have met people that are under the impression that
there are no such things as error bounds.


Indeed. All my statements are based on measurements. Before SA was
turned off, several university web sites kept continuous plots of the
wandering. Now you can do it with the internal plot on just about any
GPS.
Artio
(formerly das Bagal or even Bagal)

"Rodney Myrvaagnes" wrote in message
.. .
On Thu, 26 Aug 2004 17:47:12 GMT, "Arty Facting"
wrote:

Hi

I don't know if you know so I'll mention it anyway

Most GPS units have a measurement accuracy or inaccuracy.

It would be fine if it was consistent day-in & day-out, but it is not

It varies with signal and satellite availability and also with weather
conditions.

The reason I mention this is because you may return to bang the same

co-ords
as on the GPS and be up to 30 yards from what you wanted to find. That
being said & writ GPS units are mega-phun!

Before WAAS and while selective availability was in effect, it could
wander as far as 400 feet. However, in recent years I have found about
2 meters to be the practical limit. I check when tied up in the marina
slip occasionally.

There is no way you could come back to the wrong gravestone in an
ordinary cemetary.


Rodney Myrvaagnes NYC


We have achieved faith-based science,
faith-based economics, faith-based law
enforcement, and faith-based missile
defense.
What's next? Faith-based air traffic control?



Rodney Myrvaagnes NYC


We have achieved faith-based science,
faith-based economics, faith-based law
enforcement, and faith-based missile
defense.
What's next? Faith-based air traffic control?
  #47  
Old August 27th 04, 09:03 AM
Ron Hunter
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Posts: n/a
Default

John McWilliams wrote:
Mxsmanic wrote:

John McWilliams writes:


... which in the case of at least Macs running osX, themselves
auto-synch to atomic clocks.




Macs are furnished with atomic clocks?

No, that's extra and it's bluetooth.

Most of us, tho, prefer the server method, being rather cheaper.


And MUCH easier to carry around!
  #48  
Old August 27th 04, 09:03 AM
Ron Hunter
external usenet poster
 
Posts: n/a
Default

John McWilliams wrote:
Mxsmanic wrote:

John McWilliams writes:


... which in the case of at least Macs running osX, themselves
auto-synch to atomic clocks.




Macs are furnished with atomic clocks?

No, that's extra and it's bluetooth.

Most of us, tho, prefer the server method, being rather cheaper.


And MUCH easier to carry around!
  #49  
Old August 27th 04, 10:07 AM
Keith Sheppard
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Before WAAS

Over here in Europe, we are still in "before WAAS". There's been a lot of
testing activity of the European equivalent of late but still no public
service.

That limits GPS accuracy in Europe to about the 15ft mark for the time
being.

Keith


  #50  
Old August 27th 04, 10:07 AM
Keith Sheppard
external usenet poster
 
Posts: n/a
Default

Before WAAS

Over here in Europe, we are still in "before WAAS". There's been a lot of
testing activity of the European equivalent of late but still no public
service.

That limits GPS accuracy in Europe to about the 15ft mark for the time
being.

Keith


 




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