Bicycle Travel > GPS & Digital Data Discussion

Open Street Map?

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In reviewing this forum, one of the things that has surprised me is how little mention OpenStreetMap gets.  For those not familiar with it, it's an open map that can be edited and used by anyone.  On the web, it's like the other mapping sites, except you can say "Wait, that's wrong," and then fix it on the spot.

In GPS applications seem to have three advantages over manufacturer's maps.  Firstly, it's free, so if you're buying a cheap GPS, you don't end up paying a significant percentage more to get usable maps.  Secondly, it updates all the time.  You can notice an error on your GPS one day, edit in a fix on the site, and have a corrected, routable map on your GPS the next day.  Thirdly, there are many ways to massage the data, and there are at least a few bicycle specific treatments of the data, that optimize the maps and the routings for bikes (optionally giving preference to bikeways or tertiary roads).

While this may work with other GPS units, the focus of my reading and experimenting has been on Garmin units, which most here seem to use, as well.  The easiest way to play with OpenStreetMap maps on a Garmin (or the Garmin software on your computer) is to pull a section of the Lambertus maps, where you select the region you want maps for on their site, and they'll mail you a link to the downloads.  These maps seem optimized for car routing, making them an analogue to the City Navigator maps.  There are a couple cycle specific versions, including Cyclemap and VeloMaps, but those require rather more effort to build on your own.  I've just gotten a mostly working build for the Northeastern US using the VeloMaps encoding, and it mostly seems pretty neat, though some of the routings are a bit unexpected.

Have others played around with this?  Are the pitfalls to these maps that I haven't hit yet?  It seems the more cyclists we get using these, the better the data will get.


I downloaded the US map last night on my Edge 705 and have been experimenting with it all of today. So far so good. It took three simple steps:

* Download the map image in compressed format from The file ( that I downloaded on 30 March 2012 was 2.47GB.
* Expand the file to gmapsupp.img. Size is 3.31GB.
* Copy the image file to the Garmin micro SD card under the "garmin" folder. Note:

* My Edge 705 only supports one map image file that must have the name gmapsupp.img. Other units may support multiple files that can have different names. If you are not sure, then keep this one name.
* It takes about an hour to copy the file when the micro SD is inserted into the computer, using an adapter. It takes several hours when copying to the GPS unit using USB cable.
In general, to be safe, I use the GPX Track option from (\garmin\gpx folder), and save the TCX course file as backup (\garmin\courses folder). Both options contain breadcrumbs of the mapped route. This is safer for two reasons:

* Follow the same exact route as it was mapped on the web site. There is less risk of the GPS unit calculating its own route that may be different from the intended one.
* Maintains the directions and route even when the road happens to be missing from the map, or when the route is on a trail that is not on the map. In fact, with a TCX file from, even without a map, I still get the cue sheet prompts at turns.
The following web site allows for building custom images from selected map sections:

Plenty of instructions are at

I am still experimenting with maps and languages outside the US. I loaded Japan's map and tested a few routes:

* The text does not display properly. Kanji characters are replaced with commas and periods. Road numbers and other Roman characters do appear.
* Small roads outside major metropolitan areas seem missing from Open Street Map, even on the web site. Probably will be added in time.
I found an old discussion on this forum circa 2008 at

There is an active discussion on this topic at

I will post more results as I learn more. Pleas share your experience as well.

I have been testing the Open Source Map (OSM) on my Edge 705 for the past two months. I used it on the bicycle and in the car, in the United States and Canada.

For my most frequent use of the GPS, the map worked as expected:

* Navigates roads that are previously mapped.
* Shows detailed maps of all roads I was on, even minor ones in rural areas and inside state parks.
* Shows some services and points of interest in nearby areas. These are dependent on the information entered in OSM
* Shows turn by turn directions, prompts for each turn, distance to next, distance to destination, and other measurements.
* Could not navigate to US & Canadian addresses. The maps do not seem to recognize states. They show data at the country level. Therefore, unless the city name is absolutely unique in the entire United States (or Canada), it was impossible to enter it as part of the address.
* Because I was not able to enter my home address, I had to use its location so I can use the "Go Home" functionMore details are in following posts to keep topics separate.

Meanwhile, I would at least try to use OSM in the following cases:

* Do not own Garmin City Navigator maps. OSM is free. As far as I found, it is a snap to install.
* Traveling to an area out of coverage. At the time of this writing, for example, I cannot find Garmin City Navigator maps for Japan. An OSM map for Japan is available though.
* Traveling for a short trip to another country. Maps average at about $100. Buying a set for each trip will add up quickly.

Navigation worked exactly the same on both sets of maps: City Navigator North America & OSM.

Note the images below of navigation sequence for each map. They each contain:

* Preview of the route
* Preview of the cue sheet
* First prompt with advanced notice to turn
* Second prompt for immediate turn
The only difference between the two are the labels for roads, such as "Ridgewood Rd" versus "Ridgeweed Road", and "East St" versus "East Street (217)".

The first set of images below is for City Navigator North America:

The second set is for OSM:

Note in the previous post how the distance of the route in the two maps is calculated slightly differently. I am not sure exactly why. I think it is because they are two different maps. Roads on them are charted differently causing the discrepancy.

There is another reason. I used Google Maps on to create route. The waypoints from that route do not match exactly those on the GPS unit. Take a look at the sticky topic Using Adventure Cycling GPS Data, under the title Variations among maps.

Especially in this case, the waypoints and track points were off in some cases when using OSM.

Note in the image below:

* The first tile shows a prompt to go "Left off of Newfield Court", while there is no left.
* The second and third tiles show an extra spur for the route, followed immediately by a U-turn.

I found this misalignment to occur about once on most routes. But it is very easy to recognize.


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