I started looking into my new project the other day. The first steps will have to be extracting information from GPX or FIT files, and adding the information to a PostGIS database. I managed to do this in several ways, mostly through a combination of GPSBabel and ogr2ogr, though no single way has done exactly what I want yet: ogr2ogr automatically adds GPX data to the tables in a manner similar to what I want, but extension data (heart rate, temperature) is not treated the way I want, while the FIT data needs to be extracted first into a format readable by ogr2ogr, and then put in the right table form after being put in the database, all of which turned out to be surprisingly easy. (Even so, I may just choose to go with adding the data from GPX for now.)
The biggest problem I’ve run into so far is that GPSBabel does not extract all the data from the FIT file, and FIT is a proprietary, binary file format — I can’t get lap information, for example, just by scanning the file with awk or something. I may have to download and use the (again, proprietary) FIT SDK, in a C or other program I write myself. This may fit in well with what else I have to do, since I can call the parts of ogr2ogr I specifically need, directly from C.
Before it gets to that point though, I have to decide what I especially want to do with this data, which will tell me what I need to extract, what I need to save, and what I can disregard, or discard after processing. Do I want to build a full-blown replacement for Garmin Connect, where I keep all relevant data? Or do I want to just build something, like a web badge, to show a minimum of data about the ride, data like distance, duration and a map of the ride, with maybe a link to the ride’s Garmin activity page? I am leaning towards the minimalist approach (which would entail just saving one record per activity, with fields containing aggregate data), but I think I want at least some of the individual track point data because I may want to graph things like elevation or heart rate.
But maybe I don’t need to keep trackpoint data to build my graphs on the fly. Maybe I can make small graphs as PNG’s or GIF’s for the badge, and store those images in the database — hopefully they would be smaller than the trackpoints themselves. Alternately, I could store the entire FIT file (which is actually pretty small) in the database, and extract whatever I need on the fly. (I would still do a one-time analysis to get and store my aggregate data, since this might be a little too slow for on-the-fly data generation.) These choices will depend on the results of all the little coding/database/GIS experiments I’m doing now, extracting, converting and aggregating sample data.
Ten Years Gone: This is what I wrote on this date in 2008. We voted today, and I remain hopeful, but it is certainly not as happy a day as that one was, and even with good news I don’t think we’ll match that day.
