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OzSpider
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Joined: Aug 08, 2006
Posts: 11
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 Posted: Tue Aug 15, 2006 12:09 pm Post subject: i3 can't distinguish between two roads very close together |
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My StreetPilot i3 can't distinguish between two roads very close together.
The story : To go home I drive south along the A34 (Oxford western bypass) which is dual carrigeway, 2 lanes each way. At a certain point I turn off it and follow a suburban street (single carrigeway, 1 lane each way) which runs parallel to the A34.
The small road and the A34 are next to each other (separated by only a thin sound barrier). The i3 does not recognise that I have turned off the A34 and continues for some time to give directions as though I was still on it! (The i3's route goes along the A34, I only turn off because I prefer to go the other way).
This is not a problem for me since I know the area, but what if it happens elsewhere?
Should the i3 know I'm on a different road, or is it's resolution insufficient to detect that in this case? |
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Lester_Burnham
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Joined: Oct 17, 2005
Posts: 618
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| Posted: Tue Aug 15, 2006 12:49 pm Post subject: Re: i3 can't distinguish between two roads very close togeth |
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| OzSpider wrote: | My StreetPilot i3 can't distinguish between two roads very close together.
The story : To go home I drive south along the A34 (Oxford western bypass) which is dual carrigeway, 2 lanes each way. At a certain point I turn off it and follow a suburban street (single carrigeway, 1 lane each way) which runs parallel to the A34.
The small road and the A34 are next to each other (separated by only a thin sound barrier). The i3 does not recognise that I have turned off the A34 and continues for some time to give directions as though I was still on it! (The i3's route goes along the A34, I only turn off because I prefer to go the other way).
This is not a problem for me since I know the area, but what if it happens elsewhere?
Should the i3 know I'm on a different road, or is it's resolution insufficient to detect that in this case? |
What type of reception are you using - EGNOS or normal? |
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oddsock
Pocket GPS Verifier
Joined: May 01, 2004
Posts: 706
Location: Monmouthshire
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| Posted: Tue Aug 15, 2006 1:16 pm Post subject: |
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My Quest and 60c do the same thing even with an external arial, EGNOS enabled or not ....I can improve thing by turning off "Lock on Road" but this can cause probs else where 
Dave
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TomTom one v1,tomtom one v 3,TT Start20,Garmin Oregon 300,Nuvi 300
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Anita
Pocket GPS Moderator
Joined: Mar 15, 2006
Posts: 3219
Location: Windlesham, Surrey
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| Posted: Tue Aug 15, 2006 1:31 pm Post subject: |
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Surely this applies to all Sat Navs, and is down to the limited accuracy of gps in general?
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Anita
TomTom VIA 135 - App 12.075
UK map 1125.12264
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zogman
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Joined: Sep 05, 2005
Posts: 1417
Location: swindon uk
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| Posted: Tue Aug 15, 2006 1:53 pm Post subject: |
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| Anita wrote: | | Surely this applies to all Sat Navs, and is down to the limited accuracy of gps in general? |
agreed....but also depends on the gps's sensitivity and settings ie waas/egnos......(hope you're still my friend anita)
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Anita
Pocket GPS Moderator
Joined: Mar 15, 2006
Posts: 3219
Location: Windlesham, Surrey
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| Posted: Tue Aug 15, 2006 2:20 pm Post subject: |
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| zogman wrote: | | Anita wrote: | | Surely this applies to all Sat Navs, and is down to the limited accuracy of gps in general? |
agreed....but also depends on the gps's sensitivity and settings ie waas/egnos......(hope you're still my friend anita) |
Yes, I know waas/egnos can improve accuracy, if available.
I was really suggesting that it isn't just the i3's fault. I'm very fond of my i3, and I like to stick up for my friends (including you, of course, zogman!!)
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Anita
TomTom VIA 135 - App 12.075
UK map 1125.12264
Samsung Galaxy S21 |
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OzSpider
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Joined: Aug 08, 2006
Posts: 11
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| Posted: Tue Aug 15, 2006 2:52 pm Post subject: Re: i3 can't distinguish between two roads very close togeth |
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| Lester_Burnham wrote: | | What type of reception are you using - EGNOS or normal? |
I'm using WAAS/EGNOS. I suspect there's nothing wrong here, it's just an unfortunate consequence of GPS (in)accuracy.
I was curious to hear if anyone else had experienced this. |
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Lester_Burnham
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Joined: Oct 17, 2005
Posts: 618
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| Posted: Tue Aug 15, 2006 3:28 pm Post subject: Re: i3 can't distinguish between two roads very close togeth |
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| OzSpider wrote: | | Lester_Burnham wrote: | | What type of reception are you using - EGNOS or normal? |
I'm using WAAS/EGNOS. I suspect there's nothing wrong here, it's just an unfortunate consequence of GPS (in)accuracy.
I was curious to hear if anyone else had experienced this. |
I have whilst driving down sliproads that run parallel to motorways for a while - even with EGNOS on.
It's likely down to the i3 snapping you to the road whilst you're in the vicinity of it, and whilst it knows you've been driving down it.
Other, more advanced sat navs do have the option of turning off the "snap to road" type functionality. |
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mhb
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Joined: Dec 21, 2005
Posts: 155
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| Posted: Tue Aug 15, 2006 5:52 pm Post subject: |
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| You might find that WAAS mode availability has improved since July as since then EGNOS should have been available all the time. It's supposed to reliably increase the 5m best accuracy achieved by WAAS alone to 2m at best. |
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Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
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| Posted: Tue Aug 15, 2006 8:48 pm Post subject: Re: i3 can't distinguish between two roads very close togeth |
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| OzSpider wrote: | | I suspect there's nothing wrong here, it's just an unfortunate consequence of GPS (in)accuracy. I was curious to hear if anyone else had experienced this. |
Yes, I have seen this many times over the years.
What happens is that the position usually only accurate to within about 30 feet and the maps are sometimes off by 20 feet too so the unit has to make a guess at which road you are on. Sometimes it will jump between roads.
Things get particularly bad if you are in an area with poor reception and it's not unusual to get a position which is 300-400 feet adrift from reality. If you enter a tunnel then the unit will try to guess where you are and bluff it's way along for 5 to 10 seconds before announcing that it has no idea where you are.
EGNOS helps sometimes but not others, in my experience it only works well when you have a good view of the sky to the South-East.
The really expensive (£2000) car systems (and some of the Garmin 26xx series) have a "dead reckoning" system which monitors your speed and direction indepenently of the GPS to cater for difficult conditions.
As Lester says, some Garmins allow you to switch off "lock on road" but you only really use this when you are off road (walking, flying, boating etc) and don't want it snapping to a nearby road.
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OzSpider
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Joined: Aug 08, 2006
Posts: 11
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| Posted: Thu Aug 31, 2006 3:35 pm Post subject: |
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Original poster here - I have some additional information that might be of interest.
When I originally had the problem (where it doesn't recognise that I have turned off the main road), the i3 was navigating to a destination, and its calculated the route continued along the main road.
I tried it again, but this time with the navigation off, just in map mode. In that case, the i3 recognised that I had turned off the main road.
So, it appears the when the i3 works out where you are, when in navigation mode it tends to assume that you are following its directions, unless you really turn off a good distance.
This was with software 2.70 by the way. |
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