Sunday, 25 January 2009

In which I admit I am a dork

Instead of doing something productive today, I spent the day in San Antonio at an OpenStreetMap mapping party. I got to meet some interesting folks and play “OpenStreetMap teacher” some, and it’s nice to be reminded that at least one of my dopey childhood hobbies has some practical application in the real world. And of course I got to put some more miles on the new car, which was fun too.

Thanks to the folks at CloudMade, and particularly their community ambassador, for putting the meeting together as well as for the swag. I can’t quite figure out how they think they’re going to make money off of OSM, at least until the OSM data gets in a lot better shape, but I suppose that’s their problem and not mine.

By the way, for those who’ve hung on until this point (or were actually looking for some useful OpenStreetMap advice), here’s my GPSBabel recipe for converting NMEA track logs from my Amod AGL3080 GPS logger into GPX track logs that can be imported into OpenStreetMap:

gpsbabel -t -i nmea -f infile.log -x simplify,error=0.0005k -x discard,hdop=6 -o gpx -F outfile.gpx

Basically this throws out bad GPS fixes and simplifies all of the data to throw out any points that would deviate from the current straight line by less than 0.5 meters. At least with the Amod GPS unit once it’s got a good fix it seems to stay pretty accurate, even with the “static navigation” feature off (using the “SN OFF” firmware), as long as you don’t leave it somewhere under partial cover.

Tuesday, 16 December 2008

GPS buying advice

Rich Owings of GPS Tracklog offers advice on must-have and less-worthwhile features for an automotive GPS. I’ll slightly dissent from Rich on the value of traffic information, although of the units I’ve used the Dash Express has the only helpful implementation* of traffic I’ve found so far—and with Dash leaving the hardware business it’s not clear that anyone will be filling the gap in the future—although TomTom’s HD Traffic is allegedly headed stateside in 2009.

* Virtually all of the existing products focus on Interstates and other freeways, which might be helpful in really big cities where there are multiple freeway routes to the same destination, but isn’t so helpful in the places I’ve lived where the question is not “which freeway should I take?” but “should I take the freeway or one of the 2–3 surface street options?” Dash at least has some data on traffic on the surface street network—but much of it relies on Dash getting more market penetration, which seems unlikely unless they’ve hooked up with a major player like TomTom to provide traffic services going forward.