| Author |
Message |
Bob
Guest
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 Posted:
Mon Nov 28, 2005 1:08 am Post subject:
Crazy reading in DC |
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I drive through Washington DC a few weeks a go, and at one point on
the beltway my GPS (Garmin C330) went really crazy, the map became
wrong, and it urged me to start doing a U-turn. It recovered in less
than a mile and I didn't think much about it.
Well, coming back on Thanksgiving weekend, the exact same thing
happened in the exact same spot (never elsewhere). Since it obviously
couldn't be a satellite issue, I would think it must be a WAAS or
local correction type of error.
Just wanting to increase my knowledge of how GPS works, can anybody
possibly explain what was going on?
Thanks, Bob |
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Fred Hiltz
Guest
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| Posted:
Mon Nov 28, 2005 1:08 am Post subject:
Re: Crazy reading in DC |
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Bob wrote:
| Quote: | I drive through Washington DC a few weeks a go, and at one
point on the beltway my GPS (Garmin C330) went really
crazy, the map became wrong, and it urged me to start doing
a U-turn. It recovered in less than a mile and I didn't
think much about it.
Well, coming back on Thanksgiving weekend, the exact same
thing happened in the exact same spot (never elsewhere).
Since it obviously couldn't be a satellite issue, I would
think it must be a WAAS or local correction type of error.
|
I would guess it more likely to be a map error. Is the bad spot at
an intersection, break in the median, or overpass? I have a couple
of favorite places where my City Select map won't use an
intersection in a route because it thinks it is an overpass.
A similar case occurs when you place a via point not quite on the
road. Zoom in to see whether the route has a little stub there,
causing the C330 to send you back to it until it realizes you have
really gone past.
--
Fred Hiltz, fhiltz at yahoo dot com |
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Richard Owlett
Guest
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| Posted:
Mon Nov 28, 2005 9:08 am Post subject:
Re: Crazy reading in DC |
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Fred Hiltz wrote:
| Quote: | Bob wrote:
I drive through Washington DC a few weeks a go, and at one
point on the beltway my GPS (Garmin C330) went really
crazy, the map became wrong, and it urged me to start doing
a U-turn. It recovered in less than a mile and I didn't
think much about it.
Well, coming back on Thanksgiving weekend, the exact same
thing happened in the exact same spot (never elsewhere).
Since it obviously couldn't be a satellite issue, I would
think it must be a WAAS or local correction type of error.
I would guess it more likely to be a map error. Is the bad spot at
an intersection, break in the median, or overpass? I have a couple
of favorite places where my City Select map won't use an
intersection in a route because it thinks it is an overpass.
A similar case occurs when you place a via point not quite on the
road. Zoom in to see whether the route has a little stub there,
causing the C330 to send you back to it until it realizes you have
really gone past.
|
Relax. You *WERE* on the *beltway* weren't you ;)
Back in the 70's (paper maps -- remember them) I thought I followed
directions. Ended up in MD. First exit had State Police office. Officer
grinned, told me where I had come from, told where I intended to go,
told me how to reconcile the difference. |
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Bob
Guest
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| Posted:
Mon Nov 28, 2005 5:08 pm Post subject:
Re: Crazy reading in DC |
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Thanks. The area was fairly busy, with new construction going on that
looked like a replacement for the existing 495 bridge over the
Potomac. No via, tho, as the C330 doesn't do that.
I am getting very comfortable with the C330, but I think you can never
trust any GPS 100% - you still have to do some manual route planning
and know where you are going. I now have an informal list of errors
(all new construction) that I have to remember.
Bob
On Sun, 27 Nov 2005 21:56:44 -0600, Richard Owlett
<rowlett@atlascomm.net> wrote:
| Quote: | Fred Hiltz wrote:
Bob wrote:
I drive through Washington DC a few weeks a go, and at one
point on the beltway my GPS (Garmin C330) went really
crazy, the map became wrong, and it urged me to start doing
a U-turn. It recovered in less than a mile and I didn't
think much about it.
Well, coming back on Thanksgiving weekend, the exact same
thing happened in the exact same spot (never elsewhere).
Since it obviously couldn't be a satellite issue, I would
think it must be a WAAS or local correction type of error.
I would guess it more likely to be a map error. Is the bad spot at
an intersection, break in the median, or overpass? I have a couple
of favorite places where my City Select map won't use an
intersection in a route because it thinks it is an overpass.
A similar case occurs when you place a via point not quite on the
road. Zoom in to see whether the route has a little stub there,
causing the C330 to send you back to it until it realizes you have
really gone past.
Relax. You *WERE* on the *beltway* weren't you ;)
Back in the 70's (paper maps -- remember them) I thought I followed
directions. Ended up in MD. First exit had State Police office. Officer
grinned, told me where I had come from, told where I intended to go,
told me how to reconcile the difference. |
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