[OSM-dev] Basic GPX parser in OpenLayers

Ludwig M Brinckmann ludwigbrinckmann at gmail.com
Thu Oct 18 16:51:30 BST 2007


I very much like the GPX loading, that will come very handy for many. FYI my
track files are typically some 600KB and that seems to work fine.

I would recommend however to not draw lines between different tracks -- mine
are often separated by miles and then I get meaningless lines from the end
of one to the start of the next.

Ludwig

On 18/10/2007, Christopher Schmidt <crschmidt at metacarta.com> wrote:
>
> On Thu, Oct 18, 2007 at 04:49:06PM +0200, Joerg Ostertag (OSM
> Munich/Germany) wrote:
> > On Donnerstag 18 Oktober 2007, Christopher Schmidt wrote:
> > > On Thu, Oct 18, 2007 at 03:08:48PM +0100, Tom Hughes wrote:
> > > > In message <20071018135805.GA18708 at metacarta.com>
> > > >
> > > >         Christopher Schmidt <crschmidt at metacarta.com> wrote:
> > > > > Note that parsing Very Large data could take awhile -- I don't
> know how
> > > > > long of tracks people typically upload. The 1000 point track from
> my
> > > > > commute this morning was ~200kb -- but my GPS recording client is
> kinda
> > > > > verbose.
> > > > >
> > > > > Anyone have some examples of how big a 'large' gpx file usually is
> for
> > > > > them that I can try out for performance?
> > > >
> > > > Well http://www.openstreetmap.org/user/TomH/traces/43998 is a 26
> mile
> > > > cycle trace from last weekend - about 3.5 hours worth.
> > >
> > > Okay. That one is a bit long :) Not unbearably so. I'll take that as a
> > > target and see if I can improve performance to the extent that load
> time
> > > is tenable.
> >
> > Last time I tested the max size of GPX accepted by the osm-server was
> 5MB
> > compressed. Just for Info.
>
> Yeah, there's no way that OpenLayers is going to support drawing a GPX
> file that big -- even assuming I can figure out how to make the browser
> load the .gz compressed data properly, it's still going to be ~50mb of
> uncompressed data (if tom's 300k -> 3MB is any standard comparison), and
> that's not going to be doable.
>
> Since the point counts are available in the GPX tracklog page (it
> seems), hopefully we can at least stick it in there for GPX tracklogs
> with less than some number of points -- 1000 is ~2s to render, whereas
> 12000 was 90s, so if I do some speed improvements on it, maybe ew can
> have support for 1000-5000 points or so.
>
> Note that there will also be some slowdown for displaying the data on
> the main OSM map as well -- since the map is mercator projected, we may
> have to limit ourselves more once projection comes into play.
>
> In any case, I'll keep working on seeing what we can get
> speed/performance down to, and work on seeing if I can get support for
> getting this into OL trunk.
>
> Regards,
> --
> Christopher Schmidt
> MetaCarta
>
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