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i3 WAAS or GPS norm.
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Ash10
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PostPosted: Thu Apr 06, 2006 12:05 pm    Post subject: Reply with quote

MaFt wrote:
there's a cross roads near us - i'll try draw what it's like...

Code:

     |
     |
     |
     |------------------------ i want to turn onto this road
     |Y
     |
-----|--------------
     |X
     |
     |
     |
     |



Surely you mean:

Code:
     |
     |
     |
     |--------------+--------- i want to turn onto this road
     |Y             |
     |              |
-----|--------+     +----+
     |X       |          |
     |    +---+   +------+
     |    |       |
     |    +-------+ i3/EGNOS preferred route
     |

Twisted Evil
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Lester_Burnham
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PostPosted: Thu Apr 06, 2006 12:16 pm    Post subject: Reply with quote

Aitch2 wrote:
galaxy111 wrote:
If it's available and more accurate, why not use it?

Precisely. I cannot see the sense in anyone deliberately degrading the accuracy of their GPS device! Rolling Eyes


Deliberately degrading is something of an exaggeration.

EGNOS has only recently been available - before that, people were still using sat navs perfectly acceptably.

Using normal reception, you probably get reasonably good accuracy - certainly good enough for road / traffic use, and especially given the i3 tends to snap you to the road given a reasonable proximity.

The scenario MaFt gave, suggests more about a blip in reception - given the distances suggested - and that using EGNOS will likely be acquiring differently, rather than any improved accuracy in position, per se.

Aitch2 wrote:
I have never personally experienced any 'poor' routing with it enabled.

Aitch


And conversely, I have never personally experienced any 'poor' position, or directions on normal reception.

None of this is conclusive, or suggests that there's a warm happy setting that everybody should set out of preference.

As a generalism, the accuracy provided by EGNOS, will largely be irrelevant for driving on roads - go look at the specs for accuracy of the i3 with normal and with WAAS / EGNOS enabled.
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BERT_UK
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PostPosted: Thu Apr 06, 2006 12:42 pm    Post subject: Reply with quote

Aitch2 wrote:
I have never personally experienced any 'poor' routing with it enabled.


Lester_Burnham wrote:

And conversely, I have never personally experienced any 'poor' position, or directions on normal reception.


To be honest from a logical point of view it seems odd that your choice of GPS mode has any relevance on the route at all. Surely the GPS reception just feeds the routing algorithm with the information that you are now at point X? After all you can calculate a simulated route without any GPS signal...so what happens then?

To receive different results i'm guessing there would have to be:

1) Separate routing algorithms for each type of GPS mode
2) A bug in the WAAS\EGNOS interpretation software that is somehow affecting the routing algorithm
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MaFt
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PostPosted: Thu Apr 06, 2006 12:51 pm    Post subject: Reply with quote

actually ash, it's more like this:



with well heads being the road i want to turn on. Laughing Wink :P

MaFt
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Aitch2
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PostPosted: Thu Apr 06, 2006 12:55 pm    Post subject: Reply with quote

Lester_Burnham wrote:
Deliberately degrading is something of an exaggeration.

Not really. Unit accuracy on Normal setting cannot exceed that obtained using WAAS, and can be worse by up to a factor of 3. How else would you describe it?

http://www.garmin.com/aboutGPS/waas.html

Aitch
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Lester_Burnham
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PostPosted: Thu Apr 06, 2006 1:09 pm    Post subject: Reply with quote

BERT_UK wrote:
Aitch2 wrote:
I have never personally experienced any 'poor' routing with it enabled.


Lester_Burnham wrote:

And conversely, I have never personally experienced any 'poor' position, or directions on normal reception.


To be honest from a logical point of view it seems odd that your choice of GPS mode has any relevance on the route at all.


Odd - I'd agree with, but nevertheless, it can and has.

Aitch2 wrote:
Surely the GPS reception just feeds the routing algorithm with the information that you are now at point X? After all you can calculate a simulated route without any GPS signal...so what happens then?


I suspect that none of us, here, knows the answer to that.

But in much the same way that simulating a route from the same point, to actually getting the i3 to calculate the route in GPS mode has produced differing results for me - which is one of the main reasons I raised the inconsistent routing thing a while back - presumably the effects of different reception, or perhaps different satellites may (who knows for sure, here?) have some impact on routing.

Regardless, it definitely did have an effect. I stopped, got cancelled the route, got it to recalculate again, with the same odd route, cancelled that, switched to normal mode, got it to recalculate again, and hey presto - a more sane route.

You, I and everybody else here can only speculate as to why, without knowing an awful lot more about the internals of the i3.

Aitch2 wrote:
To receive different results i'm guessing there would have to be:

1) Separate routing algorithms for each type of GPS mode


I'm not seeing the logic behind that - surely it's equally possible there may be different parameters supplied, or different parameters affecting the calculation.

Aitch2 wrote:
2) A bug in the WAAS\EGNOS interpretation software that
is somehow affecting the routing algorithm


Or perhaps different satellites and reception pattern.

Who knows.

We can postulate on why, but that's all it'll likely ever be, the fact remains that it DID for me.
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Lester_Burnham
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PostPosted: Thu Apr 06, 2006 1:12 pm    Post subject: Reply with quote

Aitch2 wrote:
Lester_Burnham wrote:
Deliberately degrading is something of an exaggeration.

Not really. Unit accuracy on Normal setting cannot exceed that obtained using WAAS, and can be worse by up to a factor of 3. How else would you describe it?


It's an exaggeration, because normal GPS reception is accurate enough for automotive use - as it has been for years.

You're probaly going to experience from teens of feet, to maybe 20-30 feet accuracy using normal gps reception.

Likely, using EGNOS, below 10.

When you think about the size of vehicles, their speed, the size of roads, lanes, and carriageways, it's hard to see the significance of such accuracy.
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BERT_UK
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PostPosted: Thu Apr 06, 2006 2:08 pm    Post subject: Reply with quote

Lester_Burnham wrote:

Odd - I'd agree with, but nevertheless, it can and has.


That's the thing - it is odd! I'm not doubting your experiences as there seems to be at least a few people here with similar problems.

Lester_Burnham wrote:

You, I and everybody else here can only speculate as to why, without knowing an awful lot more about the internals of the i3.


True, but you never know though if someone will know andl be able to say that perhaps due to the extra inputs from WAAS/EGNOS then a different calculation is required. Or whatever the reason might be...

Lester_Burnham wrote:

I'm not seeing the logic behind that - surely it's equally possible there may be different parameters supplied, or different parameters affecting the calculation.


That would work too. My 2 points were ones that I just thought up off the top of my head. The amount of possible reasons is probably many.


I guess the only thing that can be done is to report it to Garmin and highlight times (and the locations) where this has happened so that (if they wish) they can test the reasons behind this or perhaps offer an explanation. Perhaps if people who have had this problem report it to Garmin we may see it fixed or a reason why an inconsistency may exist?
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matb
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PostPosted: Fri Apr 07, 2006 9:07 am    Post subject: Reply with quote

planned a route to exit at j11 on the a/c/w m60 (manchester) last night to a destination .3 mls off the motorway.

chose this as the slip road is some 600 yds long and follows the exact path of the main carriageway until it drops below its level at the roundabout. all that seperates the two is the barrier.

gps normal failed to notice i had taken the exit as requested and recalculated a 2 mile diversion via the next exit.

waas/ egnos noted the correct actions and i arrived at destination without diversion.

another victory for WAAS/EGNOS in an ever complicated world. Thumbs Up
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Aitch2
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PostPosted: Fri Apr 07, 2006 9:17 am    Post subject: Reply with quote

I think you're exaggerating! Wink

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matb
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PostPosted: Fri Apr 07, 2006 9:24 am    Post subject: Reply with quote

Aitch2 wrote:
I think you're exaggerating! Wink

Aitch


thats the truth i tell you, or i shall hang up my range rover keys, and walk the beat with a large rusty nail in my shoe.
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Lester_Burnham
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PostPosted: Fri Apr 07, 2006 9:51 am    Post subject: Reply with quote

matb wrote:
planned a route to exit at j11 on the a/c/w m60 (manchester) last night to a destination .3 mls off the motorway.

chose this as the slip road is some 600 yds long and follows the exact path of the main carriageway until it drops below its level at the roundabout. all that seperates the two is the barrier.

gps normal failed to notice i had taken the exit as requested and recalculated a 2 mile diversion via the next exit.

waas/ egnos noted the correct actions and i arrived at destination without diversion.

another victory for WAAS/EGNOS in an ever complicated world. Thumbs Up


Funnily enough, that's a very similar scenario that I used to see whether it would make any difference.

Longish sliproad off a motorway, that largely runs parallel for quite a while, and separated from the motorway by a barrier.

It slowly, tapers away from the motorway, and leads to a largish rounadbout under this motorway.

Now using either normal reception, or using EGNOS, it doesn't detect when I've done either - ie stay on the motorway, ignoring the route to leave it, or conversely, leave the motorway when it's directing me to stay on.

In either scenario, it only really understands that I've deviated from the route (in either normal GPS mode, or EGNOS) when I'm either just on, or just over the roundabout.

What I find odd about your first example, being that the i3 appears you to snap you to the current route and road, if you're within a certain proximity to the road - which (I suspect) is why in my scenario, the mode had no effect - it assumed I was on the correct road, whether using either normal or EGNOS.
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Milkfloat
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PostPosted: Fri Apr 07, 2006 10:03 am    Post subject: Reply with quote

MaFt wrote:
there's a cross roads near us - i'll try draw what it's like...

driving up (from bottom to top on my lovely map - any jobs navteq?!)
MaFt


Yes, plenty of jobs, what are you after?
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MaFt
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PostPosted: Fri Apr 07, 2006 10:14 am    Post subject: Reply with quote

Milkfloat wrote:
MaFt wrote:
there's a cross roads near us - i'll try draw what it's like...

driving up (from bottom to top on my lovely map - any jobs navteq?!)
MaFt


Yes, plenty of jobs, what are you after?


somewhere i can utilise my magnificent map drawing skills ;)
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Milkfloat
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PostPosted: Fri Apr 07, 2006 11:51 am    Post subject: Reply with quote

MaFt wrote:
Milkfloat wrote:
MaFt wrote:
there's a cross roads near us - i'll try draw what it's like...

driving up (from bottom to top on my lovely map - any jobs navteq?!)
MaFt


Yes, plenty of jobs, what are you after?


somewhere i can utilise my magnificent map drawing skills ;)


Too accurate for us I am afraid.
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