I discovered with my Nüvi 200 that when you turn it off, it's not really "off" if it's still receiving external power, even if you've turned it off. It just shuts the screen and speaker off. Tracks still record.

This is a little frustrating: The cleanest spot to plug a GPS into a PT Cruiser is in the center console on the unswitched 12vDC plug in the console box. Fortunately, there is a keyed one on the floorboard behind the cupholders. It's too bad there's not some kind of switch I can flip hidden off in an electrical panel that controls whether or not a circuit is keyed or always-powered. My better half doesn't want me rooting around in the car's wiring, so just gonna have to live with the keyed outlet on the floorboard until it's not under warranty anymore (or Chrysler finally goes under and makes it a moot point).

How does this relate to the project? Well, my GPX files were the size of solar systems systems. I was creating tracks hundreds of kilometers long, without leaving my parking space! Just a snarled pile of GPS points around my college and home parking lots.

So, earlier this weekend, while doing research on a couple papers I'm doing on OSM, I hacked off the extra 270,000 or so data points around Salem that were just complete garbage. I deleted all my traces from OSM, and went through with the EditGPX plugin on JOSM and hacked out obviously crap data from my GPXs. Pretty much anytime I noticed a big pile of track points in one spot, or tracks from when I was on foot or bicycle that drifted into an inaccurate mess due to buildings or plain dumb GPS placement, cut out the useless data and re-uploaded it.

Lessons I'd like to pass on to others from this experience:

1) Learn JOSM and get the EditGPX plugin. Delete bad data from your GPX files prior to uploading them.

2) Make sure your GPS is not going to keep making a trace when it's off just because it's on external power. Also, make sure you know which DC outlets in your vehicle are keyed and which are always-on.

3) When making GPS tracks on foot or by bicycle, there's definitely a right way and a wrong way to carry the GPS. Wrong: In your pocket. Wrong: In your hand. Right: In the top of your backpack. Right: In the key and coin pocket at the top of your rear pannier. Pretty much any body-mounted position is gonna cause some seriously screwy results in urban terrain.

Vancouver, BC mappers take note: Someone in your area is uploading GPX files that have horribly high DOP and just are plain unsuitable for use and adds to the jumble of trying to map downtown. If this is yours, please consider pulling your data off the database and do a sanity check on it, clean it up and re-upload just the stuff where you know you had a good GPS lock.