OpenStreetMaps are free maps which can be used with Garmin GPS's. They can be edited by anyone with an account on openstreetmap.org. Think of them as a map wiki. Kev_MacD has a great Instructable on how to add them to your Garmin Oregon GPS.
This Instructable will show you how you can upload a saved GPS track (in GPX format) to openstreetmap.org and create a trail from that data. The next time you update openstreetmaps on your device your track will be on it.
I have done an Instructable on how to create and save a track on a Garmin Oregon GPS, you should follow that if you don't know how to save a track. If you use a different brand of GPS you will need figure out how to save a track in GPX format.
Step 1: OpenStreetMaps Briefly Explained
From the OpenStreetMap.org about page:
OpenStreetMap is built by a community of mappers that contribute and maintain data
about roads, trails, cafés, railway stations, and much more, all over the world.
It is based on local knowledge - contributors use aerial imagery, GPS's and low tech field maps.
It is community driven - the community is diverse. GIS professionals, enginners running the servers and enthusiastic mappers just like you.
It is open data - you are free to use it for any purpose as long as you credit OpenStreetMap and it's contributors.
It has partners who host their servers etc
Step 2: Sign Up to OpenStreetMap
Before you are able to edit map data you must have an account with OpenStreetMap
Open the website in a browser and click on the Sign Up button.
You will need to provide an email address, Display Name and a password.
Once you have created an account go ahead and login
Step 3: Some Basic Terms
After you are logged in click on the Help then the Welcome to OSM link.
This will explain some of the terms used.
The editor I will use for this Instructable is Potlatch2, this is a flash "in browser" based editor.
A Node is a point on a map, a "dot". It can be a marker for something like a mailbox, a restaurant or a part of a way.
A Way is a line or area made up of connected nodes. It could be a trail, a road, a lake, a building, a forested area etc.
A Tag is the data about a node or a way. A node or way may have multiple tags. Using a trail for example it could show the trail name, describe the surface, what vehicles may or may not be allowed to use it etc
After we upload our GPS track we will use it to create a number of connected nodes to create a way. We will then add some tags to that way. We will then save the data we have created and add a comment so other people editing the area will know where the data came from.
I suggest you set some preferences before you try your first edit. Click on your login/display name on the top right of the page. Select My Settings. To make Potlatch2 your preferred editor click on the drop down menu under Preferred Editor: and select Potlatch2. You can also put your home coordinates in below if you know them. This will make it easy to go to your area in the map in the future and also show near by mappers when you go to your My Profile screen. Click the Save Changes button at the bottom when you are done.
Step 4: Upload a GPX Track and Lets Edit the Map.
Click on GPS Traces on the top menu, then Upload a Trace.
Browse and select the file you have saved from your GPS onto your PC as per the previous Instructable.
Put in a description, and select whether you want the trace to be public or private. Usually when I have created a GPS track while out Geocaching I make the trace/track private as it usually shows where I have been looking for Geocaches - but whatever you feel comfortable with. A tag is a word or words to describe the trace that can be used to find it. The OSM wiki suggests city or place names for tags. Note that you can delete an uploaded track later of you want.
Once uploaded you need to wait until you get a confirmation email from openstreetmap.org that the upload was successful and that the system can read the GPX file. Depending on how busy the OSM server is this could take a few minutes to an hour. Once you receive the email we are ready to start the edit. Refresh the page and click the edit link next to the GPX file name. To show the actual editing I have provided a short video of an edit I did with the track shown in the intro.
I have also uploaded a copy of the video to YouTube.
Step 5: Further Notes
Note that changes you make in OpenStreetMaps are on real data and the real map - so do not use it as a sandbox to test things. If you make a mistake or do not want to save your changes while in edit mode you can click the undo button or press the Esc key to backup through your edits. You can also just leave the page by going back to view mode or by closing your browser window without saving the changes.
I suggest your first edit is a small one, maybe a trail or path at a local park to get the feel of the editor and what is involved. Also remember to have a common node where a trail/path/road etc meet.
OpenStreetMap.org has a great wiki covering most things you would need to know about editing the maps.
Here is the main wiki page on map features (tags)
To learn more about trail/path tags see this wiki page.
Adding trails is just one of the many things you can do to improve OSM. You can add buildings, businesses, parks, mailboxes, churches, fire-stations, bus stops and dozens and dozens of other features to the map.
Feel free to contact me via my Instructables account or via username SRW in OpenStreetMaps if you have any questions. Feedback welcome.