So where does my frustration come from? I guess as many others have done, I sometimes forget to stop the Garmin at the end of a ride. This must be the old cycle computer habit. Unlike the magnetic sensor computer, the GPS does not care that your front wheel is not moving, as long as you are moving, or your bike mounted to the roof rack si moving, it keeps acquiring the waypoints.
OK, so I come home, plug the Edge into the Mac and see that my ride now has added 57.3 miles at an average speed of 60mph. Marketa says "Why do you care how many miles, vertical feet, calories etc you recorded? Did you enjoy the ride?" and she is of course totally correct. But I just cannot log such a track! And not logging anything at all for a four hour sweaty hard ride is not an option, either.
So what's the solution? Ideally, I can imagine a graphical editor which could actually open Garmin's tcx files directly without exporting them as gpx (that's dreaming now) and lets you erase route points, split tracks etc. and save the output file. Sounds simple enough to me. Here is what I tried so far:
GPS Babel: nice interface, the GUI has all the right options and buttons (some mean nothing to me), worked in splitting a two ride track into two. But would not truncate a track neither by time, nor distance, no matter what I tried. If the conversion was reported successful, then there was no track after uploading the data back to Garmin Connect.
Breadcrumbs: an online tool, looks like my GPS dream come true! After the mandatory registration, I tried and bummer, the maximum file size for uploading is 2MB.... all my gpx files are bigger than 2Mb. Otherwise, I think this is the way to go.
So I am now back to the Mac's TextEdit, which I tried before to edit XML file but ran into trouble (this is really easy on a Windows machine!). Turns out, you have to apparently change several editor settings described here. My method is to open the exported gpx file in an xml editor, find my ride end either by zero speed (could be tricky if you make frequent stops) or location (by matching to the ride start), deleting the extra block of trackpoints and changing the start time by 1 second to fool the Garmin upload to make it think this is a new track.
My next GPS experiment was going to be trying to follow a previously recorded route on the Edge 500, but I am not really sure if it is worth the frustration...