It's easy to collect GPS track logs when driving around running errands. Since I'm in the US, I don't need to gather street names for most streets; I just need tracks to align the Tiger data.

The easy thing to do is turn on my GPS logger, set it on the car dashboard, and drive around. When I get home, pick it up off the dashboard and turn it off. Easy to do, but only one problem: I am paranoid, and I don't want every public tracklog showing my driveway. Yes, it is probably silly, but there it is.

One choice is to not turn on track logging until I am a block or two away from home, and then turn it off a block or two before getting home. It works, but it can be distracting while driving. I could also edit the GPX file with a text or xml editor, but that is repetitive and boring.

The best solution is GPSBabel, which is made just for this type of thing. It has a processing filter which can include or exclude points that lie within a boundary which you define.

I'm already using GPSBabel to translate my GPS tracks from the Coto Palm GPS software into GPX format, so I figured this would be an easy addition to the process. It took more work than I expected, because of an obscure detail in the processing. GPSBabel only wants to apply the filtering to defined waypoints, and not to tracks. Fortunately, GPSBabel itself can solve this problem, too. I told it to translate the tracks into waypoints, filter, then translate back to tracks. It added waypoint names for every track point, but I could easily delete those.

The end result is a shell script looking something like this:

F=$1

NewFileName=` echo $F | sed -e 's/\.pdb$//i' | tr ' ' '_' `.gpx

#Convert trackpoints to waypoints, for exclusion to work,
# then convert back

gpsbabel \
-i coto -f "$F" \
-x discard,hdop=6 \
-x transform,wpt=trk,del \
-x polygon,file=$ExcludeFile,exclude \
-x transform,trk=wpt,del \
-o gpx -F - \
| grep -v -e '' -e '' -e '' \
>"$NewFileName"