On our aerial wildlife surveys we typically generate dozens of GPX files, and usually convert most of them into shapefiles for display in a GIS application. GPX files are a terrific way of keeping all (or almost all) of your GPS data in one place – they are xml files that store tracklog, waypoint & route information in one convenient format. They store multiple tracks, even old saved tracks from a Garmin.
I'd like to store all this track data in a spatialite database, in parallel with other tables that have point observational data from the same survey.
ogr2ogr will let me convert the track to a spatialite database:
ogr2ogr -append -f "SQLite" -dsco SPATIALITE=yes # add to table with Spatialite filetype -dsco INIT_WITH_EPSG=yes -t_srs epsg:4326 # using WGS84 SURVEYDATA.sqlite GPXFILE.gpx tracks -nln tracktable; # adding tracks to 'tracktable'
However, this imports each saved track as a line – losing the time / location information for each track point!
Anyone know of any clever ways of building a tracklog database that will preserve that information?
Tracklogs are not just a line - they are collections of sequential points, each with an elevation and time attribute. Each point belongs to a track segment, which in turn belong to a given track, and points within each track segment were taken without interruption and may be assumed to be linked. For example:
<trk><name>ACTIVE LOG</name> <trkseg> <trkpt lat="-13.471403" lon="31.382982"><ele>467.818725585938</ele><time>2009-09-09T03:53:38Z</time></trkpt> <trkpt lat="-13.471403" lon="31.382982"><ele>468.780029296875</ele><time>2009-09-09T03:53:50Z</time></trkpt> <trkpt lat="-13.471403" lon="31.382982"><ele>465.896118164063</ele><time>2009-09-09T03:54:43Z</time></trkpt> </trkseg>
Thus, to save a tracklog you need to save this collection of points with their associated data.
One solution might be to load these tracks as points, with additional columns for track name, segment, elevation and time; I don't think ogr will convert the tracks as points, though.
Thanks to @scruss who pointed out gpx2spatialite, which I installed (OS X 10.9) with
sudo easy_install gpx2spatialite. This set of tools is designed for the 'drawinglife' project (and thus has some 'city' information that is probably unnecessary for most of us); the main gpx2spatialite page doesn't explain much, but the drawinglife wiki is better. Still, lots of undocumented features - like removing duplicates!
Create a spatialite database for GPX files which will hold track segments, tracks, trackpoints and waypoints. It also has 'users' set up (which is odd, since sqlite is not a user-access system) designed to label the various tracks:
Load a whole folder of GPX files, including all subfolders, checking and removing duplicates along the way:
gpx2spatialite -s -d MyGPXArchive.db -u SL25 Selous2013/
-s= don't check if the trackpoints are in the city database (speeds it up a LOT)
-d MyGPXArchive.db= database to use;
-u SL25= add the user SL25 (just a label I used for the set of tracks collected);
Selous2013= the folder (with subfolders) that has the tracks I'm interested in.
- If you have saved tracks on an older Garmin that discards time stamp info, it'll crash the import (remove those saved tracks using a utility like GPSU).