when I make some traces using my gps I noticed (comparing my trace with another map) that they are pretty inaccurate, especially on turns and sometimes are not covered with road.
How do you draw roads or other map elements based on other users traces especially when you can’t use other sources?
Generally, you wait until you have enough GPS traces that you can take a reliable average.
Or you can display the GPS traces of other users in your desired area that were uploaded to the osm server to have an orientation how they logged ways there.
see http://wiki.openstreetmap.org/wiki/Upload for hints of processing.