Bolla, Péter wrote: > Hi, > > The problem with the timestamps come up in the case of the tracks. For > waypoints - a point feature - you can store the geographic coordinates > in the geometry, and the timestamp as an attributte. But with tracks - > which intuitively should be a linestring - you can have timestamps for > every and each node, so you can't store that as an attributte. The > current implementation of the GPX datastore in the repository extends > JTS to use 4 coordinates for every point, so it can store the > timestamp along with the geometry, and I could even define a compound > CRS with 4 axes (lat, lon, elevation, time), but no other part of the > library suports this construct. For example if I try to load a track > into udig, it will try to transform it to an other CRS, but that will > fail. > > My ideas for a solution: > - Instead of a linestring, tracks are loaded as series of point > features. This way timstamps can be saved. > - Just drop timestamps, and add the start time and end time as > attributtes. This is the way how Google Earth use GPX files. But this > way is only plausible if using as read-only datastore, as it looses > information. > - I don't really understand "complex features", but if I'm right, with > those the two previous solution could be combined: tracks would load > as an assosication between a linestring and point features for each > node of the linestring. I am afraid sharing a point between a feature and a linestring is more a function of the ISO Geometry model (sorry). > My current opinion is that both the first and second solution should > be implemented, and the user should be able to choose between them > with hints. Here is an alternative; you can ask a JTS CoordinateSequence to hold your own Coordinates that can include x,y,z and a time stamp. While this is easier with ISO Geometry (where your CRS could literally be x,y,time) you can certaintly fake it with JTS right now.
Jody ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Geotools-devel mailing list Geotools-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geotools-devel
