ICS 699 Fall 2008 week 2: GPS data displayed

Having gathered some GPS data using the AMOD AGL3080 GPS data logger, it’s time to download it and start taking a look at the data.

I’ve been meaning to read up on the AGL3080. The user manual and quick start guide are available online (they are also put onto the flash). My unit shipped with the 2.0 firmware, but the AMOD website shows they have version 2.2 now.

The GpsPasSion forum has a thread discussing the AGL3080. Lots of good info there, need to go through it all. One major issue is the static navigation feature on many GPS devices (including the AGL3080). Static navigation appears to be a hack that GPS chipset vendors have put into their devices to help car navigation software. The GPS data is filtered so that the location doesn’t jump around even when that’s what the GPS signal indicates. This is almost certainly not what I want, so I need to turn static navigation off. Luckily AMOD has created two versions of the firmware for the AGL3080: one with static navigation on, and one with it off. Need to dredge up a Windows PC to reflash the firmware though. :/

For quick experimentation, the GPS Visualizer web site looks pretty nice. It’s a web service that will slurp up raw GPS data (among other inputs) and display it in a variety of ways. Here’s my first GPS track displayed via Google Maps. This is interesting, but really what I want is the GPS data shown as little breadcrumbs, not a continuous line. GPS Visualizer has a lot of options, so perhaps this is possible. It’s not clear what happened at the end of that track where it jumps over to the pier near Ward Warehouse, as I certainly didn’t go there. Here’s the same data as a Google Earth KMZ file, where you can do a flying tour.

GPS Babel appears to be the Swiss Army knife for GPS data. It takes in a variety of GPS data inputs and spits out processed data. It’s multiplatform, and licensed under the GPL, which is nice. This looks like the way to go for local GPS data processing.

Once the GPS data has been massaged into a nicer format, the next big step is segmenting it into different transport types. I’m thinking of a multi-pass process where the first step looks for obvious possible segment endpoints such as: long periods with no satellite fix, sudden changes in speed lasting > 1 minute, and location discontinuities. A second pass goes over each inflection point and looks at the data on either side to see whether it is really a change in the type of transport (like getting out of a car and walking) or just stopping at a traffic light.

I’ll be on a mainland trip for the next week, so I don’t expect to make much if any progress between now and next Wednesday. After that I’ll be back for only 2 days before heading out to Seoul for Ubicomp and the Ubiquitous Sustainability workshop, so I’ll be focused on preparing for that in the little time I have.

I was hoping to bone up on LaTeX this week, but it didn’t happen.

Past week accomplishments:

  • Web research portfolio started
  • Downloaded first weeks’ worth of GPS data
  • Dug up information on GPS logger, found issue with static navigation
  • Generated initial plot of GPS data in Google Maps and Google Earth
  • Continued logging GPS data and travel diary

Hours worked: 10ish (target: 15 hr)

Plans for coming week:

  • Continue recording GPS data & travel diary on trip
  • Read workshop papers if they are made available

Pointers to work products:

Cool links:

  • Nothing springs to mind

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