"D" <noemail@respondhere.com> wrote in message
news:f9pdv358q4d767lpi21ua63eouhaap4gqa@4ax.com...
> On Fri, 04 Apr 2008 21:12:28 -0400, "Richard B. Gilbert"
> <rgilbert88@comcast.net> wrote:
>
> >Roger 2008 wrote:
> >> "Gordon Burditt" <gordonb.sh6xy@burditt.org> wrote in message
> >> news:XrOdnYKg7an-52vanZ2dnUVZ_vOlnZ2d@internetamerica...
> >>
> >>>>Please do not forget who the original poster was and his questions:
He
> >>>>asked:
> >>>>"can I display my own LAT/LON values somehow without a map application
?"
> >>>
> >>>For some cell phone implementation of "GPS" (this one doesn't involve
> >>>actual satellites talking to your phone), your position coordinates
> >>>are present at the cell towers and somewhere in the offices of Big
> >>>Brother, but not on your cell phone. If a map application can get
> >>>your position at all, it has to ask your cell provider to send it,
> >>>and that may cost money.
> >>
> >>
> >> Oh yeah, now that you mention it. My first camera phone called it GPS
but
> >> when you read further about it, it was just using cell phone towers.
> >>
> >> BTW I have met a person with an iPHONE that thinks his phone has GPS
and he
> >> even showed me "Google Maps for Mobile" on it.
> >>
> >> I thought he had a messed up GPS reading because it had us way across
the
> >> street and then I learned later the iPHONE uses cell phone towers for
an
> >> approximate location on "Google Maps for Mobile."
> >>
> >>
> >
> >GPS, or at least the civilian version of it, is only accurate to within
> >about 300 feet or 100 meters. I once did a "site survey" using a
> >Motorola M12+T GPS timing receiver. The software I used plotted
> >something like 10,000 position readings on the map. The result was a
> >strip about 10 meters wide and 100 meters long and oriented ENE-SSW. My
> >antenna was more or less in the middle of this mess.
> >
> >The military uses a different set of signals from the same satellite and
> >gets accurracy good enough for weapons targeting. This level of GPS is
> >available only to the military and certain defense contractors. Us
> >lowly civilians can't get it.
> >
> >As far as I know, a cell phone tower has no means of determining the
> >direction your signal is coming from.
>
> Towers cannot tell what direction the signal is coming from, but can
> tell from relative power how far away it is, and form a circle based
> on that reading. For sake of argument, say you are 3 miles from
> tower one, and 5 miles from tower two. there are only two places you
> can be 3 milies and 5 miles from the towers. Add a third tower, and
> you only have one place you can be. That is how triangulation (hence
> the tri - three) works.
With no disrespect for the poster that started this thread then how does VOR
for airplanes work from one transmitting site?
But the above site doesn't come right out and say if they use more than one
transmitting tower to get VOR to work.
I have been under the assumption that since most cellphone towers have three
elements that the cellphone knew that it was 1 of 3 directions away from the
tower but now it seems there is nothing VOR related in cell phone towers.
On Fri, 04 Apr 2008 21:50:07 -0500, Gordon Burditt <gordonb.00byx@burditt.org> wrote:
>>GPS, or at least the civilian version of it, is only accurate to within
>>about 300 feet or 100 meters. I once did a "site survey" using a
>>Motorola M12+T GPS timing receiver. The software I used plotted
>>something like 10,000 position readings on the map. The result was a
>>strip about 10 meters wide and 100 meters long and oriented ENE-SSW. My
>>antenna was more or less in the middle of this mess.
>There's also something called Differential GPS, which uses a transmitter
>on the ground to broadcast corrections. That supposedly improves
>the reading, if and where a DGPS transmitter is available.
It was a bigger deal when consumer GPS had a built in 200' error.
I worked on a differential GPS system used by a local phone company to track
their service trucks. The error from a fixed unit was subtracted from the
mobile units to remove their error. Apparantently, the 200' error was the
same over a large region.
AZ Nomad wrote:
> I worked on a differential GPS system used by a local phone company to track
> their service trucks. The error from a fixed unit was subtracted from the
> mobile units to remove their error. Apparantently, the 200' error was the
> same over a large region.
It's surprising. For a while there was a DGPS server on the net. I was using
DGPS data from other parts of the country and getting more accurate fixes
(as compared to time-averaged position fixes).
--
$109,000,000 in income! Capitalism works GREAT for Billary...
...why does she want Marxism for us?
In article <47F6D1FC.5010200@comcast.net>,
"Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
> Roger 2008 wrote:
> > "Gordon Burditt" <gordonb.sh6xy@burditt.org> wrote in message
> > news:XrOdnYKg7an-52vanZ2dnUVZ_vOlnZ2d@internetamerica...
> >
> >>>Please do not forget who the original poster was and his questions: He
> >>>asked:
> >>>"can I display my own LAT/LON values somehow without a map application ?"
> >>
> >>For some cell phone implementation of "GPS" (this one doesn't involve
> >>actual satellites talking to your phone), your position coordinates
> >>are present at the cell towers and somewhere in the offices of Big
> >>Brother, but not on your cell phone. If a map application can get
> >>your position at all, it has to ask your cell provider to send it,
> >>and that may cost money.
> >
> >
> > Oh yeah, now that you mention it. My first camera phone called it GPS but
> > when you read further about it, it was just using cell phone towers.
> >
> > BTW I have met a person with an iPHONE that thinks his phone has GPS and he
> > even showed me "Google Maps for Mobile" on it.
> >
> > I thought he had a messed up GPS reading because it had us way across the
> > street and then I learned later the iPHONE uses cell phone towers for an
> > approximate location on "Google Maps for Mobile."
> >
> >
>
> GPS, or at least the civilian version of it, is only accurate to within
> about 300 feet or 100 meters. I once did a "site survey" using a
> Motorola M12+T GPS timing receiver. The software I used plotted
> something like 10,000 position readings on the map. The result was a
> strip about 10 meters wide and 100 meters long and oriented ENE-SSW. My
> antenna was more or less in the middle of this mess.
>
> The military uses a different set of signals from the same satellite and
> gets accurracy good enough for weapons targeting. This level of GPS is
> available only to the military and certain defense contractors. Us
> lowly civilians can't get it.
>
> As far as I know, a cell phone tower has no means of determining the
> direction your signal is coming from.
It's been changed for a few years, now more like 15 meters. Clinton was
the one that changed that.
There is supposedly a new civilian GPS system in the works, one that
uses more satellites and with technolgy that allows for obstructed views.
Also supposed to be far more
Kurt wrote:
> "Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>> GPS, or at least the civilian version of it, is only accurate to within
>> about 300 feet or 100 meters.
>
> It's been changed for a few years, now more like 15 meters. Clinton was
> the one that changed that.
SPS provides accuracy's of (for position, the accuracy with respect to
geographic, or geodetic coordinates of the Earth) within:
100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
(99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
--
$109,000,000 in income! Capitalism works GREAT for Billary...
...why does she want Marxism for us?
clifto wrote:
> Kurt wrote:
>
>> "Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>
>>>GPS, or at least the civilian version of it, is only accurate to within
>>>about 300 feet or 100 meters.
>>
>>It's been changed for a few years, now more like 15 meters. Clinton was
>>the one that changed that.
>
>
> http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>
> SPS provides accuracy's of (for position, the accuracy with respect to
> geographic, or geodetic coordinates of the Earth) within:
> 100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
> (99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>
"What is the status of Selective Availability (SA)?
Effective as of Midnight 01 May 2000, Selective Availability has been set to
zero."
"THE WHITE HOUSE
Office of the Press Secretary
For Immediate Release May 1, 2000
STATEMENT BY THE PRESIDENT REGARDING THE UNITED STATES' DECISION TO STOP
DEGRADING GLOBAL POSITIONING SYSTEM ACCURACY
Today, I am pleased to announce that the United States will stop the
intentional degradation of the Global Positioning System (GPS) signals
available to the public beginning at midnight tonight. We call this
degradation feature Selective Availability (SA). This will mean that
civilian users of GPS will be able to pinpoint locations up to ten times
more accurately than they do now. ..."
News wrote:
> clifto wrote:
>> Kurt wrote:
>>
>>> "Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>
>>>> GPS, or at least the civilian version of it, is only accurate to
>>>> within about 300 feet or 100 meters.
>>>
>>> It's been changed for a few years, now more like 15 meters. Clinton
>>> was the one that changed that.
>>
>>
>> http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>
>> SPS provides accuracy's of (for position, the accuracy with respect to
>> geographic, or geodetic coordinates of the Earth) within:
>> 100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300
>> meters (99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>
>
>
>
>
> "What is the status of Selective Availability (SA)?
>
> Effective as of Midnight 01 May 2000, Selective Availability has been
> set to zero."
>
>
> "THE WHITE HOUSE
>
> Office of the Press Secretary
>
> For Immediate Release May 1, 2000
>
> STATEMENT BY THE PRESIDENT REGARDING THE UNITED STATES' DECISION TO STOP
> DEGRADING GLOBAL POSITIONING SYSTEM ACCURACY
>
> Today, I am pleased to announce that the United States will stop the
> intentional degradation of the Global Positioning System (GPS) signals
> available to the public beginning at midnight tonight. We call this
> degradation feature Selective Availability (SA). This will mean that
> civilian users of GPS will be able to pinpoint locations up to ten times
> more accurately than they do now. ..."
My Garmin GPS routinely gets accuracy to within 13 - 15 _feet_. A
freind with the same GPS often gets down to 6 feet, although he's on the
east coast and I'm in the upper midwest. - David
David wrote:
> News wrote:
>
>> clifto wrote:
>>
>>> Kurt wrote:
>>>
>>>> "Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>>
>>>>> GPS, or at least the civilian version of it, is only accurate to
>>>>> within about 300 feet or 100 meters.
>>>>
>>>>
>>>> It's been changed for a few years, now more like 15 meters. Clinton
>>>> was the one that changed that.
>>>
>>>
>>>
>>> http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>>
>>> SPS provides accuracy's of (for position, the accuracy with respect
>>> to geographic, or geodetic coordinates of the Earth) within:
>>> 100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300
>>> meters (99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>>
>>
>>
>>
>>
>> "What is the status of Selective Availability (SA)?
>>
>> Effective as of Midnight 01 May 2000, Selective Availability has been
>> set to zero."
>>
>>
>> "THE WHITE HOUSE
>>
>> Office of the Press Secretary
>>
>> For Immediate Release May 1, 2000
>>
>> STATEMENT BY THE PRESIDENT REGARDING THE UNITED STATES' DECISION TO
>> STOP DEGRADING GLOBAL POSITIONING SYSTEM ACCURACY
>>
>> Today, I am pleased to announce that the United States will stop the
>> intentional degradation of the Global Positioning System (GPS) signals
>> available to the public beginning at midnight tonight. We call this
>> degradation feature Selective Availability (SA). This will mean that
>> civilian users of GPS will be able to pinpoint locations up to ten
>> times more accurately than they do now. ..."
>
> My Garmin GPS routinely gets accuracy to within 13 - 15 _feet_. A
> freind with the same GPS often gets down to 6 feet, although he's on the
> east coast and I'm in the upper midwest. - David
Same with my HP iPaq hw6515, and GlobalLocate A-GPS accelerates time to
3-D fix.
News wrote:
> clifto wrote:
>> Kurt wrote:
>>
>>> "Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>
>>>>GPS, or at least the civilian version of it, is only accurate to within
>>>>about 300 feet or 100 meters.
>>>
>>>It's been changed for a few years, now more like 15 meters. Clinton was
>>>the one that changed that.
>>
>>
>> http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>
>> SPS provides accuracy's of (for position, the accuracy with respect to
>> geographic, or geodetic coordinates of the Earth) within:
>> 100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
>> (99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>
> "What is the status of Selective Availability (SA)?
What does SA have to do with the 2008 accuracy specification I posted?
--
$109,000,000 in income! Capitalism works GREAT for Billary...
...why does she want Marxism for us?
David wrote:
> My Garmin GPS routinely gets accuracy to within 13 - 15 _feet_. A
> freind with the same GPS often gets down to 6 feet, although he's on the
> east coast and I'm in the upper midwest. - David
My GPS III+ does at least that well most times. Note that the government
doesn't guarantee our GPSes will always be that good.
--
$109,000,000 in income! Capitalism works GREAT for Billary...
...why does she want Marxism for us?
clifto wrote:
> News wrote:
>
>>clifto wrote:
>>
>>>Kurt wrote:
>>>
>>>
>>>>"Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>>
>>>>
>>>>>GPS, or at least the civilian version of it, is only accurate to within
>>>>>about 300 feet or 100 meters.
>>>>
>>>>It's been changed for a few years, now more like 15 meters. Clinton was
>>>>the one that changed that.
>>>
>>>
>>>http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>>
>>>SPS provides accuracy's of (for position, the accuracy with respect to
>>>geographic, or geodetic coordinates of the Earth) within:
>>>100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
>>>(99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>
>>"What is the status of Selective Availability (SA)?
>
>
> What does SA have to do with the 2008 accuracy specification I posted?
>
IIRC, SA encrypted the low order bits in order to prevent GPS being used
for weapons targeting and other anti-social behavior.
Richard B. Gilbert wrote:
> clifto wrote:
>> News wrote:
>>>clifto wrote:
>>>>Kurt wrote:
>>>>>"Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>>>
>>>>>>GPS, or at least the civilian version of it, is only accurate to within
>>>>>>about 300 feet or 100 meters.
>>>>>
>>>>>It's been changed for a few years, now more like 15 meters. Clinton was
>>>>>the one that changed that.
>>>>
>>>>http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>>>
>>>>SPS provides accuracy's of (for position, the accuracy with respect to
>>>>geographic, or geodetic coordinates of the Earth) within:
>>>>100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
>>>>(99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>>
>>>"What is the status of Selective Availability (SA)?
>>
>> What does SA have to do with the 2008 accuracy specification I posted?
>
> IIRC, SA encrypted the low order bits in order to prevent GPS being used
> for weapons targeting and other anti-social behavior.
That's true, but Clinton shut it off in 2001 and it hasn't been a problem
for nearly seven years now.
--
$109,000,000 in income! Capitalism works GREAT for Billary...
...why does she want Marxism for us?
On 2008-04-07, clifto <clifto@gmail.com> wrote:
> Richard B. Gilbert wrote:
>> clifto wrote:
>>> News wrote:
>>>>clifto wrote:
>>>>>Kurt wrote:
>>>>>>"Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>>>>
>>>>>>>GPS, or at least the civilian version of it, is only accurate to within
>>>>>>>about 300 feet or 100 meters.
>>>>>>
>>>>>>It's been changed for a few years, now more like 15 meters. Clinton was
>>>>>>the one that changed that.
>>>>>
>>>>>http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>>>>
>>>>>SPS provides accuracy's of (for position, the accuracy with respect to
>>>>>geographic, or geodetic coordinates of the Earth) within:
>>>>>100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
>>>>>(99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>>>
>>>>"What is the status of Selective Availability (SA)?
>>>
>>> What does SA have to do with the 2008 accuracy specification I posted?
>>
>> IIRC, SA encrypted the low order bits in order to prevent GPS being used
>> for weapons targeting and other anti-social behavior.
>
> That's true, but Clinton shut it off in 2001 and it hasn't been a problem
> for nearly seven years now.
Sure, but no one in the government said they wouldn't turn it back on if
they felt like it which is why their SPS accuracy claims still always
include the effects of SA.
In fact the paragraph just above the accuracy specifications you quoted
says, in part,
"The SPS accuracy specifications, given below, include the effects of SA."
which, I guess, is what SA has to do with the 2008 accuracy specification
you posted.
Dennis Ferguson wrote:
> On 2008-04-07, clifto <clifto@gmail.com> wrote:
>
>>Richard B. Gilbert wrote:
>>
>>>clifto wrote:
>>>
>>>>News wrote:
>>>>
>>>>>clifto wrote:
>>>>>
>>>>>>Kurt wrote:
>>>>>>
>>>>>>>"Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>>>>>
>>>>>>>
>>>>>>>>GPS, or at least the civilian version of it, is only accurate to within
>>>>>>>>about 300 feet or 100 meters.
>>>>>>>
>>>>>>>It's been changed for a few years, now more like 15 meters. Clinton was
>>>>>>>the one that changed that.
>>>>>>
>>>>>>http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>>>>>
>>>>>>SPS provides accuracy's of (for position, the accuracy with respect to
>>>>>>geographic, or geodetic coordinates of the Earth) within:
>>>>>>100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
>>>>>>(99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>>>>
>>>>>"What is the status of Selective Availability (SA)?
>>>>
>>>>What does SA have to do with the 2008 accuracy specification I posted?
>>>
>>>IIRC, SA encrypted the low order bits in order to prevent GPS being used
>>>for weapons targeting and other anti-social behavior.
>>
>>That's true, but Clinton shut it off in 2001 and it hasn't been a problem
>>for nearly seven years now.
>
>
> Sure, but no one in the government said they wouldn't turn it back on if
> they felt like it which is why their SPS accuracy claims still always
> include the effects of SA.
>
> In fact the paragraph just above the accuracy specifications you quoted
> says, in part,
>
> "The SPS accuracy specifications, given below, include the effects of SA."
>
> which, I guess, is what SA has to do with the 2008 accuracy specification
> you posted.
>
> Dennis Ferguson
> Dennis Ferguson wrote:
>> On 2008-04-07, clifto <clifto@gmail.com> wrote:
>>
>>>Richard B. Gilbert wrote:
>>>
>>>>clifto wrote:
>>>>
>>>>>News wrote:
>>>>>
>>>>>>clifto wrote:
>>>>>>
>>>>>>>Kurt wrote:
>>>>>>>
>>>>>>>>"Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>>GPS, or at least the civilian version of it, is only accurate to within
>>>>>>>>>about 300 feet or 100 meters.
>>>>>>>>
>>>>>>>>It's been changed for a few years, now more like 15 meters. Clinton was
>>>>>>>>the one that changed that.
>>>>>>>
>>>>>>>http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>>>>>>
>>>>>>>SPS provides accuracy's of (for position, the accuracy with respect to
>>>>>>>geographic, or geodetic coordinates of the Earth) within:
>>>>>>>100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
>>>>>>>(99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>>>>>
>>>>>>"What is the status of Selective Availability (SA)?
>>>>>
>>>>>What does SA have to do with the 2008 accuracy specification I posted?
>>>>
>>>>IIRC, SA encrypted the low order bits in order to prevent GPS being used
>>>>for weapons targeting and other anti-social behavior.
>>>
>>>That's true, but Clinton shut it off in 2001 and it hasn't been a problem
>>>for nearly seven years now.
>>
>> Sure, but no one in the government said they wouldn't turn it back on if
>> they felt like it which is why their SPS accuracy claims still always
>> include the effects of SA.
>>
>> In fact the paragraph just above the accuracy specifications you quoted
>> says, in part,
>>
>> "The SPS accuracy specifications, given below, include the effects of SA."
>>
>> which, I guess, is what SA has to do with the 2008 accuracy specification
>> you posted.
>>
>> Dennis Ferguson
>
> Bingo.
Except that the specs they show are with the old SA settings, not the
current zero setting.
Dutch wrote:
> News wrote:
>
>
>>Dennis Ferguson wrote:
>>
>>>On 2008-04-07, clifto <clifto@gmail.com> wrote:
>>>
>>>
>>>>Richard B. Gilbert wrote:
>>>>
>>>>
>>>>>clifto wrote:
>>>>>
>>>>>
>>>>>>News wrote:
>>>>>>
>>>>>>
>>>>>>>clifto wrote:
>>>>>>>
>>>>>>>
>>>>>>>>Kurt wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>>"Richard B. Gilbert" <rgilbert88@comcast.net> wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>>GPS, or at least the civilian version of it, is only accurate to within
>>>>>>>>>>about 300 feet or 100 meters.
>>>>>>>>>
>>>>>>>>>It's been changed for a few years, now more like 15 meters. Clinton was
>>>>>>>>>the one that changed that.
>>>>>>>>
>>>>>>>>http://www.navcen.uscg.gov/faq/gpsfaq.htm#Standard
>>>>>>>>
>>>>>>>>SPS provides accuracy's of (for position, the accuracy with respect to
>>>>>>>>geographic, or geodetic coordinates of the Earth) within:
>>>>>>>>100 meters (2 drms) horizontal 156 meters (2 Sigma) vertical 300 meters
>>>>>>>>(99.99% prob.) horizontal 340 nanoseconds time (95% prob.)
>>>>>>>
>>>>>>>"What is the status of Selective Availability (SA)?
>>>>>>
>>>>>>What does SA have to do with the 2008 accuracy specification I posted?
>>>>>
>>>>>IIRC, SA encrypted the low order bits in order to prevent GPS being used
>>>>>for weapons targeting and other anti-social behavior.
>>>>
>>>>That's true, but Clinton shut it off in 2001 and it hasn't been a problem
>>>>for nearly seven years now.
>>>
>>>Sure, but no one in the government said they wouldn't turn it back on if
>>>they felt like it which is why their SPS accuracy claims still always
>>>include the effects of SA.
>>>
>>>In fact the paragraph just above the accuracy specifications you quoted
>>>says, in part,
>>>
>>> "The SPS accuracy specifications, given below, include the effects of SA."
>>>
>>>which, I guess, is what SA has to do with the 2008 accuracy specification
>>>you posted.
>>>
>>>Dennis Ferguson
>>
>>Bingo.
>
>
> Except that the specs they show are with the old SA settings, not the
> current zero setting.
>
Correct, which voids the OP's accuracy and error probabilities.
News <News@Group.name> wrote in
news:d5idnf8SFKwgUmfanZ2dnUVZ_t3inZ2d@speakeasy.ne t:
> Correct, which voids the OP's accuracy and error probabilities.
>
>
With the zero setting, and the fix not moving around constantly, the
accuracy of GPS is most dependent on having a clear view of the majority of
the satellites with minimal multipath propagation caused by high buildings,
bridges, mountains, towers and anything else reflecting the incoming
signal.
In a clear parking lot, with more than 6 satellites in direct view, it will
place the GPS in its location in a single parking space with no multipath
in flat country. In city canyons of high rise buildings where the actual
direct view of the sky is only a few degrees in most directions, you're
lucky if it stops going crazy in the area of the whole aforementioned
parking lot at the mall. It'll be all over the place as you move around,
even walking and really screwing it with multipath going in a dozen
directions at once.
GPS is very dependent on TIMING, the time it takes the signal to get from
the precisely transmitting bird to your receiver's fixed delay. http://electronics.howstuffworks.com/gps.htm
This website does a great job, in a series of sections, to show how GPS
works and that TIMING is EVERYTHING in the GPS system. The text is nicely
detailed without becoming the math monster of spherical trig the scientific
websites quickly become. Just take the calculations for granted.
It's really quite neat how the cheap GPS gets an atomic reference clock for
free (displaying it on your screen, quite handily).
To really see what TIMING means to your GPS accuracy with awful multipath
making the paths from the birds go crazy, just take your GPS mapping box
into an open restaurant with a metal roof to block out the direct signals
and large windows on at least 2 sides so the signals can bounce around off
the traffic, buildings, etc., the GPS can see through the window. Move
away from the windows far enough so you cannot see the sky from your table.
Sit, eat, and watch the crazy patterns of a system gone mad.....
> News <News@Group.name> wrote in
> news:d5idnf8SFKwgUmfanZ2dnUVZ_t3inZ2d@speakeasy.ne t:
>
>> Correct, which voids the OP's accuracy and error probabilities.
>
> With the zero setting, and the fix not moving around constantly, the
> accuracy of GPS is most dependent on having a clear view of the majority of
> the satellites with minimal multipath propagation caused by high buildings,
> bridges, mountains, towers and anything else reflecting the incoming
> signal.
>
> In a clear parking lot, with more than 6 satellites in direct view, it will
> place the GPS in its location in a single parking space with no multipath
> in flat country. In city canyons of high rise buildings where the actual
> direct view of the sky is only a few degrees in most directions, you're
> lucky if it stops going crazy in the area of the whole aforementioned
> parking lot at the mall. It'll be all over the place as you move around,
> even walking and really screwing it with multipath going in a dozen
> directions at once.
>
> GPS is very dependent on TIMING, the time it takes the signal to get from
> the precisely transmitting bird to your receiver's fixed delay.
> http://electronics.howstuffworks.com/gps.htm
> This website does a great job, in a series of sections, to show how GPS
> works and that TIMING is EVERYTHING in the GPS system. The text is nicely
> detailed without becoming the math monster of spherical trig the scientific
> websites quickly become. Just take the calculations for granted.
>
> It's really quite neat how the cheap GPS gets an atomic reference clock for
> free (displaying it on your screen, quite handily).
>
> To really see what TIMING means to your GPS accuracy with awful multipath
> making the paths from the birds go crazy, just take your GPS mapping box
> into an open restaurant with a metal roof to block out the direct signals
> and large windows on at least 2 sides so the signals can bounce around off
> the traffic, buildings, etc., the GPS can see through the window. Move
> away from the windows far enough so you cannot see the sky from your table.
> Sit, eat, and watch the crazy patterns of a system gone mad.....
That's where "assisted GPS" (aGPS), as used on many cell phones like my
V3m helps out. By getting much of the satellite data via the cell signal
using data from the tower's GPS, the accuracy is enhanced, even within
buildings or other situations where the sat signals are partially
obstructed. Your location is also pinpointed much faster, since a lot of
the computations are handled by external computers instead of in the
handset. It's still much more accurate outside in the clear of course...
Dennis Ferguson wrote:
> In fact the paragraph just above the accuracy specifications you quoted
> says, in part,
>
> "The SPS accuracy specifications, given below, include the effects of SA."
Missed that. Cranial flatulence. Thanks.
--
$109,000,000 in income! Capitalism works GREAT for Billary...
...why does she want Marxism for us?
Re: simple GPS lat/lon display? 
Linear Mode
