Garmin 800 going its own way

[Hammerman]

I did The Transporter 200 audax yesterday and used my 800 as a sat nav, but it kept on wanting to take me on its own route instead of the one I programed into it.  The route was uploaded as a TCX file and usually its ok but yesterday it kept on wanting to take me back to the start. If I looked closely at the screen the programed route was there as a white line but all the directions wanted me to follow the thick pink line that was going totally the wrong way. Because of this I had to periodically tap the screen to see the map which resulted in the battery going much faster. Luckily I had a powermonkey on me and I recharged the unit between the control at Defynnog and the top of the Devils Elbow, but that meant I now have 2 half routes recorded instead of one. Am I doing something wrong or is it just having a funny turn? It has been working good up until now. p.s. I uploaded the route via ridewithgps
Hammerman

[tiermat]

So it looks like the 800 has the same issue as the 705.  If you don't pass the start, or close enough to it, it will keep re-routing you back to the start.

Nothing you can do apart from you make sure you pass the start, easiest done by moving the start point to a short way after the actual start (as I found out with the routes I have planned for York pub rides, I now start the route at the crossing after the station, not actually at the station).

[frankly frankie]

All the Garmins do it.  The 'next' point in the route always has to be closer than any later point in the same route, or it will short-cut.

[Hot Flatus]

I never have that problem with my 705 using the gpxx file extension. Try it.

[Jaded]

Ditto for me.

[Hammerman]

Thanks I'll give it a try

[Hot Flatus]

In case you don't know, plot on bikehike and choose gpxx route as download option 

[Jaded]

If you have the right libraries/drives installed you can download straight to the device.

[Hot Flatus]

Better to keep a hard copy, for next year 

[fossil]

I've just (2 weeks ago) got a 800
 what is the difference between a gpx and a gpxx ?

 I plotted a route for the first part of the South downs way , put it on the 800 as a (red line route)  gpx  but it kept coming up as the pink one , which seemed to work but kept giving me directions when on the road sections
 I must admit I haven't read the instructions cos I'm a bloke

  A

[Feanor]

So it looks like the 800 has the same issue as the 705.  If you don't pass the start, or close enough to it, it will keep re-routing you back to the start.

Nothing you can do apart from you make sure you pass the start, easiest done by moving the start point to a short way after the actual start (as I found out with the routes I have planned for York pub rides, I now start the route at the crossing after the station, not actually at the station).

I spent some time testing the behaviour of my Garmin Montana 600 unit regarding how it navigates 'routes', because there are several possible ambiguities.   Here's how that unit behaves...

Some background things to bear in mind:
- Navigating simply to a destination ( no route ) will cause the machine to auto-route as it sees fit from your current position to the destination waypoint.

- A route is simple a list of intermediate waypoints, which are navigated to in order.   Between waypoints, the machine auto-routes as it sees fit, as above.   To reduce the machine's scope for doing this, use more intermediate waypoints to force things.

So the questions I needed answering:

-Missed start waypoint
If my route is ( say ) home - various waypoints - destination, what happens if I start 10m down the road from my home?   Will it spend all day trying to route me back home because I didn't 'touch' the first base yet?

Answer is:  It depends...   If it detects that I'm already *actually on* the route, it will navigate me to the next waypoint.    However, if I were *not* actually on the route, ( perhaps I'm starting out a couple of streets away ) then yes, it would try to navigate me to the 'home' waypoint first.  If I ignore it, and go ahead and join the route at some distance in, then the moment it determines that I've actually joined the route, it will stop trying to navigate to 'home', and will begin navigating to the next waypoint.

-Missed Intermediate Waypoints
What happens if I need to skip a waypoint ( eg a diversion )?
Will it spend the remainder of the day insisting I go back and touch the mised wpt?

Answer is: Same as above.
As soon as I deviate from the route, it will re-calculate and try to navigate me back to the missed wpt.   It will continue to do this, even if I come close to a later part of the route.   It will not try to join me back to the route at a later point, even if that's much closer than the missed wpt.   However, if I ignore it and re-join the route at a later point anyway, then as soon as I actually re-join the route it recognises this and gives up on any 'missed' waypoints and begins navigating to the 'next' wpt.

Dunno how the 800 behaves, but the above is the results of my experiments, and the unit does behave consistently.

[De Sisti]

-Missed start waypoint
If my route is ( say ) home - various waypoints - destination, what happens if I start 10m down the road from my home?   Will it spend all day trying to route me back home because I didn't 'touch' the first base yet?

I found this out on the Upper Thames Audax in November. I had the route in both my Edge 200
and Etrex Vista CX. As my first waypoint wasn't near the village hall start, once on route, both
units tried to steer me back to that first waypoint.

On my home rides now, I use Mapsource and have the first waypoint (it will be an A001) just 
before the end of my road (about 50 metres away). Once the unit(s) have picked up the first
waypoint routes me pretty well. (there have been a couple of spurious directions, but I put it
down to me not checking the waypoints properly before downloading them the the garmin).

[fossil]

So I take it the Garmins are a bit stupid , and you have to point them in the right direction if you want them to help you find YOUR way ?

[Feline]

I treat my Garmin as so stupid it is not required to do any working out for itself. I upload the way I want to go as a .tcx 'course' and then simply follow the pink line. There is no scope for disaster. If you go off course then the unit bleeps and tells you this within 6 feet but leaves it up to you to find your way back on again. You can mark controls as generic coursepoints with their names, and mark turnings where you think you might need a bleep and reminder on bikehike or similar. Bikehike can write the course straight to the Garmin if it's hooked up to your PC. This method is very simple and foolproof in my hands. I haven't tried to use a .gpxx since the day I got lost about 6 times with one of these on Jaded's thunderbox ride!
For PBP I created 2 .tcx courses, one for Paris-Brest and the other for Brest-Paris. Even with a 600k course it worked perfectly.

[phil d]

-Missed start waypoint
If my route is ( say ) home - various waypoints - destination, what happens if I start 10m down the road from my home?   Will it spend all day trying to route me back home because I didn't 'touch' the first base yet?

I found this out on the Upper Thames Audax in November. I had the route in both my Edge 200
and Etrex Vista CX. As my first waypoint wasn't near the village hall start, once on route, both
units tried to steer me back to that first waypoint.

I've had this issue many times, generally because the last waypoint is closer to the start than the first - I assume it is trying to take me round the route backwards.  Provided you know how to get to your first waypoint (following everyone else seems reasonable at the start!) you only have to switch off and on again and it should navigate faultlessly.

[frankly frankie]

Bingo. 
As mentioned upthread - in normal 'dumb' autorouting mode, the GPS will shortcut to any later point in the route, if it can.  The key is in the word 'shortcut' - it's trying to help! 
The solution is to arrange for your 'next' point to always be closer than any other subsequent point - which sounds much more complicated than it is, actually it's just common sense and if the route were not a circuit, would be automatic.

But the gpxx methods described upthread sound like a much better way of following a circuit anyway.

So I take it the Garmins are a bit stupid , and you have to point them in the right direction if you want them to help you find YOUR way ?

If you're looking for a handlebar-mounted SatNav, none of the models discussed here are that.  (With the arguable exception of the Montana.)
There are three reasons for this:
1) Garmin hand-holdable or bike-specific GPSs aren't optimised for SatNav duties.  They will do it, but badly.
2) Even car satnavs notoriously are far from perfect.  We've all heard the stories of car drivers attempting to cross non-existent river bridges etc.  More to the point there are frequent minor diversions and subsequent recovery, that the driver barely notices.  Each involves no more than a few extra gear changes and a few drops of spent fuel.  That's OK in a car, but on a bicycle the same process wouldn't be tolerable - no cyclist likes to be sent the wrong way, even for a second, and for good reason.
3) Second-guessing the sort of routing choices that a cyclist would instinctively make, seems to be very difficult to do.  At every junction you make choices based on road business, gradient, surface quality, scenery, wind direction, general state of tiredness, etc.  Then there are walk-throughs, footbridges and the occasional useful bridleway (in amongst all the useless ones), that a cyclist may or may not decide to use. The proof of this is that in current Garmins where there is a choice of 'Cycling' mode or 'Car' mode, though neither is perfect for most of us the Car mode works better, the cycling mode is that bad.