GPS and OSM

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A few weeks ago I got a Garmin Dakota 20 GPS mainly for us to use when touring. Don’t get me wrong I do love the old paper maps, could spend hours looking at them. But a GPS will cut down the faffing with them while on route as it is easier for us to find out where we are, if we should be off the beaten track or in other words – lost.

I did have a quick dip into GeoCaching, pretty much treasure hunt with your GPS. I can see the fun in it and it pretty amazing that there is all these little treasures hidden all over the world. Though I don’t think it is something I will pick up and do much of.

What really tickles my fancy right now is OpenStreetMap, as free wiki map that you, yes you, can update and add too. I have already found a few places that were wrong to what is there in real life.

One thing I don’t get with the auto routing that you can set your GPS to do is how the heck it plans/plots a route. Sometimes it does not make sense whatsoever. Yes it is some sort of mathematical calculation the GPS does and it comes up with a suited route for us to take.

Last night I plotted out a route to take to work, yes I knew where to go but I’m trying to learn how to use this Dakota 20, before our big trip down under. So to see how it would warn me about an upcoming turn, I planned it to take a left one road earlier than I normally take when I head east from where we live.

Planned route: Head down Studdridge Street turn left into Chipstead Street then right onto New Kings Road, simple.

Route taken: Head down Studdridge Street turn left into Perrymead Street then right onto New Kings Road, simply because that is what I do every time I go that way and I forgot to follow the GPS.

Route re calculated route: As you can see on the map a big massive loop around. And the GPS was dead keen on that route until I got onto New Kings Road. It is funny that it does not see that Perrymead leads up to New Kings Road and it would be shorter to continue all the way to New Kings Road than doing the detour loop. Even when that right tour into Ryecroft Street is less than 50 yards away from New Kings Street.

Well I take it that this GPS thing is still learning and would get better in time. So lesson learned from this do not blindly rely on you GPS.

I have learnt that you can plot a Track to show you where you are going, a trick I picked up over on yacf.co.uk very helpful bunch over there. So when the Auto Routing wants you to go somewhere you can see if is on track so to speak and is not sending you on a wild goose chase.

2 COMMENTS

  1. There you have it, why I am happy to use the 305 on a bike and didn’t want anything that routed (although tbh it would be nice to have a map picture sometimes). I suspect the Dakota will be worth its weight in saffron when you hit the open road, though. Just not in town.

  2. It is important to ensure that the routing settings on the GPS unit match up with those assumed by whoever made the map. Most OSM cycling maps work by telling the map that motorways are slow, poor-quality roads and cycle ways are fast, good quality roads. It’s defined in the lines style file if mkgmap is used.

    A consequence of this is that you should NOT tell the GPS to avoid highways, or choose bicycle routing. Just pretend to be a car, and the GPS will use what it has been told are the best roads (cycleways, roads with cycle lanes, and the like) and will avoid what it has been told are the poor/slow roads (motorways, trunk roads, etc).

    Hope that helps. In any case, to know the best settings to use on the device, you need to know how the map was made.

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