GPS Maps ... an adventure
 

Went for a 30 mile ride yesterday with my wife. We rode a route that I've ridden several times, although a first for her. At one point we stopped at the top of a hill under the shade of a tree to rest, next to a paved road that turns off and winds up a hill into the vineyards. I saw a cyclist disappear around a corner which got me to wondering where this road went. I pulled out my cell phone and loaded the GPS app to find my location and saw that the "unknown" road made a nice loop and rejoined the same road we were on a couple miles ahead. By this point in the ride my wife wasnt particularly interested in riding more hills, particularly if the road was unknown. She carried on along our route and would wait for me ahead where this new road rejoins. Off i went, up, up, up. Great views of the valley, the vineyards and orchards below. Two miles into the loop, according to the GPS i should be approaching the original road only to discover the road ends in the middle of a vineyard. My GPS shows the road as continuing, but it wasn't anything more than a tractor's path at best. I phoned my wife, who was already wondering where I was to let her know that despite only being half a mile or so from her that I would be riding back the way I came. Can't say that I was disappointed by the adventure, just a little surprised by the lack of accuracy in the GPS mapping. I'd ride that road again if even just for the views.

I've found that GPS maps are frequently at least a small bit off, and sometimes off in a big way. I used to do a lot of geocaching out in the boonies, and I was amazed at how often the silly thing would try to route me through some farmer's field, down a private (locked gate) road, or something else unexpected. Don't blindly trust them. Remember the words of a famous philosopher: The map is not the territory.


Mike

My wife and I drove to a relatives new house, plugged in the address, and where following the directions. It took us on a route that went through a US Army installation. Our pleasant drive was suddenly interupped by a half a dozen guys standing in front of us with *****s. It was one of those "I don't think this is the right road" moments. Luckly we had plenty of room to turn around before things got, interesting.

The GPS is always accurate within stated tolerances. The problem is with the map upon which GPS data is superimposed. It is really, really hard for the map makers to keep current on changes. That is compounded by local naming conventions. Some, I swear are named as a result of wishful thinking or marketing hope than anything else.

To me it is foolhardy to blindly follow any navigational device or chart. You didn't do that. You had an out if things didn't go as planned. Wise decision.

A half mile on a tractor path? What's the problem? :)

Sure, let me ride home and get the bike with larger tires :) 700x23c and road shoes, I don't think so. Besides, the ride back out offered a little more climbing and great views. Who doesn't enjoy the opportunity to ride another hill?

https://farm3.staticflickr.com/2933/...68a0b3a4_c.jpg

A tractor path is still a navigable road. I wouldn't call that inaccurate.

Same thing sort of happened to me riding out in the Hamptons last week. In trying to reach the beach while staying as long as possible on a road with a nice bike lane, I detoured onto a road that looked like a good shortcut between the two main N/S routes, the second of which had no bike lane at all and that I wanted to spend as little time on as I could. (I knew this road came out the other side as paved, as I had seen it many times.) About a mile in the pavement went away. Not too bad, packed gravel. Then it turned to loose sand...with 25mm tires. Urgh. Paved on both ends, MTB territory in the middle. Had to go back north through a development to stay on pavement. Added a couple mile to the trip, all told, so not so bad, but still surprising. :rolleyes:

GPS sites show my driveway as a road. I have no idea why.

Unless there are big rocks or soft ground, 23mm tires are fine. You can ride lots of dirt, gravel and even some single track on a road bike with no problem. And you won't know unless you try it.

I went to a different part of a town about 10 miles out form home. Saw a "trail" that I had never sen before on Google maps, thought I'd check it out. It was at the bottom a pretty tough hill, so no problem getting there. Come to find out the "trail" was actually a concrete culvert with about 2 feet of clearance to the roads it cut under. I had to trudge back up the hill I just came down. Would of been cool except it was crappy chip and seal with gravel patches where gravel driveways washed out down on to it. Nothing to see either.

Sometimes like the OPS experience it can be an adventure of sorts though. I spotted a road I had never noticed cutting through to a lane I had already been on, I could not for the life of me figure out where this came out at, I could not remember seeing the road from the other side. I went down the road that lead to it, down a giant hill and came up to a cattle fence completely blocking the road. It even had a name on the maps too. For some reason it was cut off and not even anyone from the city knew why. Later that year I tried to figure out where it came out on the lane on the other end. I spotted another closed lane, little more than a cattle trail only about 1 car width wide with a big swinging gate blocking it. I made a few loops in front of it to "mark" it on my GPS and when I checked it out in SportTracks it WAS the entrance of the road. To this day anyone I ask about it seems to know nothing about it.

Now I usually scope out a "new" route in the car first, THEN try it on the bike if it pans out.

There are roads that are driven by Google or what not before going in the map database, and some roads (or 'roads') that came pretty much from aerial photography and drawn in without much concern as to whether they're drivable.

I worked on GPS navigation for nearly a decade, in the pre-Google Maps days and back then it was a lot like what the original poster described than today.

In anyone's map there should be entry bits for the class of road, and other useful information. But this may not be displayed to the end user, only used to make routing decisions etc.

Perhaps with one of the other bikes ... I was riding my baby. I'd sooner walk barefoot carrying my bike than subject it to the gravel. The best option of course was to turn around and ride back. Good thing for cell phones, even if the GPS maps steer you wrong, I could phone my wife to let her know that I'd be a while.

Also interesting to see that my experience is not unique. Could start a thread ... all the places we've ridden that we never expected

Years ago a few friends and I used to do Sunday rides without benefit of maps (long before GPS). We'd kind of know the lay of the land, and our rides followed the simple rule that whoever was up front at the moment could make any turn. So one day riding in the lower Catskills , we found a small road and followed it for miles, working ourselves up a valley until it petered out at some farm near the saddle between two peaks.

Faced with a long trip back to the turn, I suggested that over the hill there had to be another road serving another farm and leading back eventually to a branch of the same river we started on. So we hoofed it across the farm, avoiding the grazing cows (no bull around) up and ver the hill and sure enough found a road back down. 80 or so miles later we got back to start.

For a few years after that, riding to the ends of valleys, and hiking to the next if necessary was a regular feature of our riding, and opened up loops that we never would or could ride otherwise.

BTW- farmers are nice people, and not one ever said an unkind word about our little trespasses.

We sometimes encounter roads closed for construction (which we usually transit anyway),
but there are also errors like below...

http://bikeforums.net/attachment.php...hmentid=397911

If you got that when clicking "by bike" I wouldn't consider it an error. It was clearly passable with a bike, and might have offered a route that otherwise wouldn't show.

OTOH if it showed up as a route for a car, then it was an error, and you might send them a correction.

BTW- you didn't say, but did the step by step directions say anything about "cross tracks, go around fence"?

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