[Loadstone] gps accuracy

Rusty Perez rustys.lists at gmail.com
Tue Oct 31 05:40:28 GMT 2006


Hi!
Thanks for the response.
What's this about differencial GPS?
Sometimes I press the 3 key on my phone in loadstone and I get a "gps
fix" response. Sometimes I get a differencial fix. What does this
mean?
I do have the WAAS feature on, I think, so things should be good. As I
understand it, the gps coordinates for intersections may not be super
accurate, so this may be some of what I'm noticing as well. Often when
I get to an intersection, loadstone says it's 20 yards away.
I understand that it's not perfect and, truth be told, I could
certainly find something better with this than with out it. I'm just
trying to understand the imperfections.

Thanks!
Rusty


On 10/30/06, Shawn Kirkpatrick <shawn at odyssey.cm.nu> wrote:
> There will be drift with any gps receiver. Normal gps accuracy is around 15
> meters. This can be improved if your receiver can use waas, then the
> accuracy may be around 3 meters. These numbers will vary depending on the
> number of satellites the receiver is using, weather conditions and other
> factors. When you save a point the more satellites and the lower the
> accuracy reading the better. When looking for a point it will double shift.
> This usually doesn't work out as bad as it sounds. If you save a point with
> a good signal and then have a good signal while looking for it again the
> accuracy can be very good. This is just the limits of consumer grade gps. If
> you want better you'd need a military grade gps or a very expensive gps
> receiver that can use differential gps correction. As the technology
> improves accuracy will improve as well. A gps will get you very close to
> where you want to be but you'll still need a bit of skill to get to exactly
> where you want to be.
>
> On Mon, 30 Oct 2006, Rusty Perez wrote:
>
> > But Monty,
> > if there is this drift asociated with a star III receiver, is it
> > possible that waypoints which I enter will be very inaccurate? If the
> > point floats when I'm recording it, then if it floats as I look for
> > it, doesn't that make it doubly shifted? :-)
> >
> > Thanks
> > Rusty
> >
> >
> > On 10/29/06, Monty Lilburn <monty at loadstone-gps.com> wrote:
> >>
> >> Hi Rusty,
> >>
> >> I can not comment on the accuracy of the US intersections as I do not
> know
> >> the margin of error on those points.  I would imagine they should be
> >> within 20 metres or so if I were to guess.
> >>
> >> Most Serf3 receivers claim accuracy of between 5 and 15 metres 3-5 metres
> >> if your receiver is using WAAS.  GPS receivers will get you to the
> >> building, not necessarily to the door!  They usually work very well for
> >> identifying an intersection, bus stop or train station!
> >>
> >> The drift you experience when standing still is normal with the Star 3
> >> receivers.  Star 2 receivers do not have this drift problem but are not
> >> nearly as sensative in terms of picking up satellites.  Most people don't
> >> mind putting up with a bit of drift for the added sensitivity of the Star
> >> 3.
> >>
> >> Monty
> >>
> >>
> >> On Sun, 29 Oct 2006, Rusty Perez wrote:
> >>
> >>> Hi folks,
> >>> I'm new to this, but I'd like to know more about the accuracy of my
> >>> sirf3 gps receiver--Holux gpslim236, and accuracy of waypoints ETC.
> >>>
> >>> The documentation says it should be accurate to 2.5 meters or
> >>> something like that. What I find is that when I go through an
> >>> intersection, even in a car, the waypoint that loadstone anounces with
> >>> this gps receiver is never all that close. If it's ten meters away,
> >>> that's close. Does this mean that the waypoints which are on the us
> >>> geological survey are not that accurate, or is my gps really that off?
> >>> Also, when I'm stationary, even right on top of where I have just
> >>> placed a waypoint, it seems to wander, sometimes one meter, sometimes
> >>> 6 or 7 meters.
> >>>
> >>> Does this error correction we have in the program really help? How do
> >>> I know if it's on; there are an on and an off sellection.
> >>>
> >>> Should I try and get a sirf2 receiver?
> >>>
> >>>
> >>> Thanks for any enlightenment I will receive.
> >>>
> >>> Rusty
> >>> _______________________________________________
> >>> Loadstone mailing list
> >>> Loadstone at loadstone-gps.com
> >>> http://www.loadstone-gps.com/mailman/listinfo/loadstone
> >>>
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