How do cycle GPS give turn guidance?

Encoste

When I lived in Ireland I knew all the tracks and had others show my but I am living in another country and now I need to use a GPS to navigate routes I have downloaded from the internet.

I have been trying to do my research and I understand how to download and use files but my question is how the route guidance is given.

On a cars GPS the gps obviously works out your route and gives you turn by turn guidance because it knows when you are approaching a junction and by the fact that you have to navigate by the road network. So, when navigating off road, and on a MTB trail, the GPS is not aware that you are coming to say a fork in the trail as the other branch of the track is not mapped. How does that work out in practice? Does one spend a lot of time taking the wrong turn and then back tracking? Or do you just try and keep an eye on the direction arrow to stay on the right trail?

Tenzor07

Do you mean you want a map that will tell you "turn right at big rock, or left at oak tree?"

Encoste

Thanks for your helpful reply. If you think it's such a silly question then why did you waste the effort to reply?

What I want to know is how the guidance is given and how well it works in reality because of the obvious limitation of not having all the trail network in the database. How well does it keep you on track with say a very narrow angled fork in the trail?

seamus

As far as I know, you can buy MTB-specific trail maps for devices with turn-by-turn directions. Same as you would if you were offroading in a jeep or quad. So if there's a fork in the trail it tells you to keep right/left.

Obviously specific trails have to be covered by the maps though, and I don't know what coverage in Ireland is like, given our pathetic number of trails.

hardCopy

I don't have a proper GPS device, but I believe some use what they call a breadcrumb trail, basically a dotted line on the screen that you try to follow. I'd imagine a bit of observation and willingness to change plan is required using them off-road though.

seamus

Also, http://www.mapsntrails.com/en/ireland/trails

Encoste

Thank you, As mentioned I won't be using it in Ireland but I think the situation in Spain is similar.

I was thinking of the situation where you would be on a single track through a forest and there are many alternative tracks leading off and you are whizzing along that it wouldn't be very practical to try and keep an eye on the screen and you might spend a lot of time backtracking to missed turns.

but I believe some use what they call a breadcrumb trail, basically a dotted line on the screen that you try to follow.

That's what I understood from the manufacturers literature. It makes me question why, then, I need a €200-300 GPS unit over a map in the first place. However I see a lot of them on other peoples bikes so I assumed I am missing something?

triggermortis

I think you're expecting a lot of a GPS to pick one of a few trails with accuracy. My Garmin Edge 500 has problems following a route on a straight road - often telling me "you are off course" when there are no turns to take.
The GPS knows where you are in terms of latitude and longitude, and uses the changes in those numbers as you move to decide where you are, the speed you got there and all the other data, but it cannot tie it all accurately and quickly to a map - at least not in a device only costing 200 quid!
I've not used or seen the higher end 800 or any other proper mapping GPS units, but you may just have to get used to your local trails with a map.

Stokolan

With the edge 705 on the road It beeps within a few hundred meters of the turn and pops an arrow on the screen. I have never been on trails so not sure how it works for that.

Dermot Illogical

Encoste wrote: »

It makes me question why, then, I need a €200-300 GPS unit over a map in the first place. However I see a lot of them on other peoples bikes so I assumed I am missing something?

Mostly they're used to record where you've been, with optional cadence and HR data, not to navigate.

Micilin Muc

I don't do MTBing but I run on (non-MTB) trails in the Dublin Mountains. Before I got to know the area inside-out I used to mark the trail out on gpsies.com and download it to my Garmin and use the map function. If I came across a tight fork on the map while marking the route, I would exaggerate the line I created to make it more obvious on the watch. There is a landmark feature on the map too that you could use ...