What is crowdsourcing? Well it is kind of like it sounds where the general public can collaboratively contribute to build something (online). Wikipedia is and example of crowdsourcing or mass collaboration as they also call it. In terms of mountain biking it could be about collaborative descriptions but the focus here is going to be on collaborative maps. The trails for some sites can be tagged with descriptions so you can add that to. Rather than try to reinvent the wheel and attempt to build a crowd mapping effort on this site, existing efforts are going to be listed and in some cases explained. This is a work in progress.
Here are a few crowdsourcing type sites.
http://www.everytrail.com/ This is a newer one that is being supported by Google Earth. It has a smart phone app and you can add photos and comments! Check it out.
http://www.opencyclemap.org/ This is just a viewer with terrain type topo information added for Open Street Map
http://openmtbmap.org/ How to make mountain bike maps with OpenStreetMap data
http://toposm.com/ This is just a viewer with terrain type topo information added for Open Street Map
http://www.mtbguru.com/ upload your gps and everyone can view them
http://www.switchbacks.com/nwtrails/ upload and view your gps
http://www.gpsfiledepot.com/maps/view/134 GPS upload download with helpful tips
Open Street Map This is probably one of the largest crowdsourcing map sites. For instance OSM is playing a big role in the Haiti earthquake response effort. People from all over the world are adding to it every day. Think OSM is for third world countries, Euros and geeks here in the US? Have a look at this blog post talking about how Microsoft is now backing OSM for Bing and one of the founders of OSM is joining Microsoft. In another example, Mapquest uses OSM for the UK and has donated a million dollars to improving OSM in the U.S. in hopes of making that a viable option here. There are also apps where you can cache OSM to Android phones not to mention being able to put OSM on your GPS. (see the OSM tutorial videos below)
Here is the basic way it works. You upload your GPS tracks as GPX "traces". Then you have to trace trace your tracks so to speak and give them attributes like a name and type of surface etc. The process of tracing is called "digitizing" by map makers. Latter you or anyone else can edit those lines or attributes.
Here are some pointers to help with the process. The GPS files have to be gpx files with time stamps. You can tell if the gpx file has time stamps by opening it in a basic text editor like notepad. This means for a lot of units you can't save the track because when you do it strips out the time information. So in order to get the GPS file with time stamps for some units you have to use the active log before you save it. With the MapSource Garmin software you connect to your GPS unit and download the tracks. The active track should be there. Delete the tracks you don't want from MapSource clean up your active log of any errant looking segments and export this track out as a GPX file with an appropriate name. A GPX file is the standard exchange format recognized by almost everybody.
Next go to Open Street Map (OSM) and create a user name and password. There is a tab on the OSM page called GPS Traces. This is where you will upload your gpx track files. This page has entries being uploaded from all over the world all the time. At the top of the page there is a link called "See just your traces, or upload traces" Here you just browse for your file and upload it. You can tag this file with all sorts of information but it does not show up in the final map. If it is successful or not, it will let you know. Depending on the amount of traffic there may be a bit of a delay before your data is accepted and added to the site. It will be listed on the GPS traces tab when it is ready to be used for editing.
After your gpx file has been uploaded the next thing to do is to go to the edit tab and if you are still logged in you can either edit live or edit with save. There is a little button on the lower left that looks like a gps unit. If you click on this it will display all the gps tracks that have been uploaded, including yours hopefully. Now you have to "trace" that GPS track. If you hold the left mouse button down you can pan the map. If you click somewhere you don't want you have to wait until later after you save it to fix it or start over unfortunately. There is another editor called JOSM that is more powerful but it is involved to install so it is not covered here. When you are done you double click to finish the line. Then you can start adding tags like the name and so on. If you screw up the tags you or anyone else can change them latter if you or they are logged in. One thing that may trip you up a little is that the attribute drop down showing in the lower left after you finish your line has an associated add attributes button on the opposite side of the screen on the lower right for some reason. The initial drop down doesn't give you the choice you need for mountain bike trails and that is Highway = Path. You can do this with the add button on the right.
Why do they make you digitize your track? Probably because most recreational gps units are not all that accurate and the original focus was on roads. Plus a lot of folks have GPS files that are less than kosher with extraneous lines going all over the place. They want you to ground truth your editing with the imagery which if current is probably more accurate than your gps. The imagery is probably not going to be of much help for mountain bike trails so that is just a limitation of the process you have to live with.
There are some video tutorials out there like this one. http://showmedo.com/videotutorials/series?name=mS2P1ZqS6
Or how about these three most excellent tutorial videos made by ORMTB.
OSM to GPS web pages
Topographic maps for Garmin devices using OSM data If you make it through this process you have earned your outdoor geek badge.
It is not a problem if more than one person uploads gpx files of the same place. In fact this would be helpful because if you go to draw \ trace a new trail there could be a bunch of gps tracks showing. So if one of the units was getting bad signals in one area you can average them out to pick the most likely location of the trail. Recreational GPS units are not all that accurate, especially in the woods, as you will see when there get to be ten files of say Phil's trail. They will not be all in exactly the same place.
There should however only be one line for a trail in OSM when you are not editing for all the world to see. Lets say you just got a twenty thousand dollar survey grade GPS unit for your birthday and you are sure some existing trail is not very accurate. You would upload your gpx file and then move the existing line work to it. You could then make a comment about the accuracy of your edits.
That is it for now this is a work in progress. Feel free to contact me if you are working on OSM and trail mapping especially here in Oregon.