GPS track accuracy

(RIP) willstatt · Apr 7, 2003

Does anyone else find that their recorded tracks are quite inaccurate? I have a GPS V, but the question is aimed at owners/users of any model or make really.

If I go for a ride, the load up the resulting track onto my Mapsource on my PC, then there are many cases where the track is not recorded as it was actually travelled. In some cases this will be shown on the Mapsource, as if I had detoured across a field, then back onto the road. Sometimes if two roads are running parallel, it will show a track as if I had travelled partly on the wrong road.

Now the above isn't really a problem for general use, but if I use my unit for offroading, (which I will do) then god knows where it could lead me if I did a back track!!!

I've also found recently, that I lose satellite reception quite a lot, and yet the unit is mounted on my bars, and the weather has been clear, so wondered if I've got a fault on my unit, or if others were having similar problems?

Please let me know

Many thanks Will

Dot.Com · Apr 7, 2003

I think this comes down to how regular a track log entry is saved. I have also seen this happen in poor coverage areas, where the signal has dropped for a period and a dead reckoning fix was used to create to point. Also, be aware of vibration, which certainly affected my unit when mounted on the bars without a proper bracket; it would reset or switch off at certain speeds, probably because the batteries were vibrating and upsetting the units power supply electronics.

The GPS 3+ uses an automatic point interval by default, which I think depends on speed and changes in heading to decide how often to record a point. I think it is lulled into a sense of security if you have been on a steady heading for a while, and if you then make a sudden change in direction it is 'caught out' and records a point soon after. The only problem is that the software draws a straight line from one point to the next, making the track look a bit wrong!

-phil

(RIP) willstatt · Apr 7, 2003

tracks

It had occured to me that vibration may be playing a part, though, I did buy my unit from Bracken, who do some sort of anti vibration modification on the units they sell for bikers. Also, I have it in a Touratech mount, which does have foam shock absorbers, and also it's wired into the bikes electrics, so no battery problem.

I know what you mean by the track 'marker' spacing, and I've seen how when travelling fast, this can result in the track appearing to cut a corner.

What I'm getting is something different though.. it's just as if every so often it throws up a random incorrect coordinate, and hence I get tracks that show on Mapsource as heading off up a road for several hundred yards when I haven't even gone up that road.

No once else getting bad reception either... on any trip, I seem to get 'bad satellite reception' messages at least once every 20 mins I reckon, even if only for a short time.

Any ideaS?

Will

Gecko · Apr 7, 2003

Will
I have the GPS V too - I don't use a TT mount , I use a RAM mount and I have never heard of any modifications for bikers being done to the GPS V unit....sounds like sales talk to me.
My track accuracy is bang on - I have used it several times to re-run routes that I rode the previous summer and it's superb.

Having said that I was out riding this weekend and I was suprised to see that the track was not following a road at all - it was trail blazing a virgin screen as I rode along.....after about 5km it joined up with the road again but the roads I was riding seemed to have been there quite a while. They were not recently laid new roads so I was a bit puzzled by this phenomenon.
I know map coverage isn't always perfect but this time I was puzzled. I blame Uncle Sam myself - I reckon they have been messing with the GPS sattellites so they can find their way around Iraq

judge · Apr 7, 2003

Gecko I can't comment on the accuracy thing except the one we all know about (i.e. the piss-poor accuracy of the basemaps) but the modified unit is no mis-nomer on the part of the salesman. Brackens units (this might be all Touratech ones I dunno) are opened up and the components are modified to make them more robust. I tell no lies...

adamski49 · Apr 7, 2003

Will

My GPS V seems to be pretty accurate o far - no bizarre routes as yet but it did think I had turned off the M6 at Birmingham when I was going though some roadworks - may be a new bit of tarmac?

As for reception I only dropped reception a couple of times on a 400 mile round trip and only for a short while so nowhere near as bad as yours.

One thing I did do when I got the unit was to remove the antenna and clean both contacts with a cotton wool bud - plenty of light dust but nothing major. Just an idea but it may improve the connection.

I've also had the unit turn itself off a couple of times - I guess this is related to vibration or jolts on rough roads. I was giving it some on a B road at the time and didn't see it turn off.

I just assumed the batteries had died but when I turned it back on it stayed on for the next 1 1/2 hours to home so obviously not.

HTH

Adam

Gecko · Apr 10, 2003

judge said:
Gecko I can't comment on the accuracy thing except the one we all know about (i.e. the piss-poor accuracy of the basemaps) but the modified unit is no mis-nomer on the part of the salesman. Brackens units (this might be all Touratech ones I dunno) are opened up and the components are modified to make them more robust. I tell no lies...

I stand corrected yer honour

...never knew this was the case. Do they charge more for the units that have been modified ?

Gecko · Apr 10, 2003

Will
Just a thought - go into your menu on the GPS V and check in the system tab if you have WAAS enabled. I do and I don't have the problem you are getting - just an idea maybe.......

adamski49 · Apr 11, 2003

Don't quote me on this but I didn't think WAAS worked outside the US... as a result mine is currently disabled.

The driving along in a field scenario seems to happen with v4.00, not sure why.

Adam

judge · Apr 11, 2003

Gecko said:
I stand corrected yer honour ...never knew this was the case. Do they charge more for the units that have been modified ?

Oh yes!! Though at the time I got a bit of a deal on the stuff I bought - don't know now whether this stuff has gone over to Nick Plumb with Touratech or has stayed at Bracken. Essentially the standard one was OK except if you used it extensively on the ruff stuff then (and usually just after the warranty had expired) the units would require a return to Garmin for an out of warranty repair, I understand over the life span of the Garmin II, III, III+ and V this has been quite a good screw for Garmin. Knowing Touratech's pricing even the standard item would've been cheaper elsewhere

Gecko · Apr 11, 2003

adamski49 said:
Don't quote me on this but I didn't think WAAS worked outside the US... as a result mine is currently disabled.

The driving along in a field scenario seems to happen with v4.00, not sure why.

Adam

Dunno mate - but mine is enabled - maybe it's not doing anything but there again....maybe it is

Gecko · Apr 11, 2003

judge said:
Oh yes!! Though at the time I got a bit of a deal on the stuff I bought - don't know now whether this stuff has gone over to Nick Plumb with Touratech or has stayed at Bracken. Essentially the standard one was OK except if you used it extensively on the ruff stuff then (and usually just after the warranty had expired) the units would require a return to Garmin for an out of warranty repair, I understand over the life span of the Garmin II, III, III+ and V this has been quite a good screw for Garmin. Knowing Touratech's pricing even the standard item would've been cheaper elsewhere

I should be ok then - if it looks like I'm going to start hammering it I'll visit Bakes for some donut filling - that should keep things nice n' in place

I have done a bit of light off roading with the GPS on board and no problems so far. Mind you some of the roads over here are bumpier than riding off road anyway.....

Banjaxed · Apr 11, 2003

No WAAS in Europe

It won't matter if you have WAAS enabled or not - there's no infrastructure in Europe to broadcast the correction signals. See here.

GPS track accuracy

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