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#41
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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
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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
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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
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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 |
#45
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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
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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
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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
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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
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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
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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 |
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