[OSM-talk] relating trace points to gpx files

[Andy Robinson]

It's a tough job to find that short 100m section where the gps was off in a
many km log file so I leave them well alone unless the whole track is bad,
in which case I don't bother to upload it to OSM.

Cheers

Andy

Andy Robinson
Andy_J_Robinson at blueyonder.co.uk 

>-----Original Message-----
>From: talk-bounces at openstreetmap.org [mailto:talk-
>bounces at openstreetmap.org] On Behalf Of Etienne
>Sent: 14 July 2006 15:33
>To: Andrew Loughhead
>Cc: Talk Openstreetmap
>Subject: Re: [OSM-talk] relating trace points to gpx files
>
>One thing about this is that there will always be some "bad" trackpoints in
>OSM.  If you look at any city centre you'll see that the tracks can be very
>scattered.  It's quite common for a GPS to be "off" because it has picked
>up a reflected signal from a tall building.
>
>Over time, with many passes along the same street there will eventually be
>a strong _average_ scatter of the  trackpoints that will be be a good
>approximation to the actual line of a road, but many of the points will be
>quite a distance from the line and sometimes a very long distance.  Take a
>look at central London if you want to see streets with many thousands of
>trackpoints.
>
>As for whether you should cleanup/edit your tracklogs before uploading them
>- I've not seen any serious discussion here on that subject, but since the
>tracklogs are supposed to represent the raw data from which the refined
>maps are created I wonder if its actually a good thing to manually edit
>them before uploading?
>
>Etienne
>
>
>On 7/14/06, Andrew Loughhead <andrew at incanberra.com.au> wrote:
>
>	On Fri, 2006-07-14 at 09:59 +0200, Erik Johansson wrote:
>	> On 7/14/06, Andrew Loughhead <andrew at incanberra.com.au> wrote:
>	> > On Wed, 2006-07-12 at 10:57 +0200, Erik Johansson wrote:
>	> > <--snip-->
>	> > > A far as I know (from reading the code)  when you delete a GPX
>file,
>	> > > the points will be marked invisible. So they will disappear
>from the
>	> > > rendered images.
>	> [...]
>	> > I have been able to delete all my files and start loading them
>	> > individually, checking each result in JOSM.
>	>
>	> Oh no... This thing about deleting GPX traces. I don't like it, we
>	> should never make people delete the files. I think it's blasphemy
>to
>	> remove data from the traces db.
>
>	I have finally found my problem file. As is traditional, it was the
>last
>	file I looked at. I have deleted the 20 odd garbage track points,
and
>	all data has been re-sent to OSM.  So far the applet display still
>shows
>	the bad points.
>
>	I could have found the bad data without deleting files from OSM, if
I
>	had tried a little harder (or to be honest, actually turned my brain
>	on). But it was an effective, if tedious, way of finding where the
>bad
>	points came from.
>
>	Andrew.
>
>
>
>
>
>	>
>	> I also use josm and I do it like this:
>	> 1. load GPX file
>	> 2. download GPS traces for that area
>	> 3. upload GPX file to OSM
>	> 4. edit
>	>
>	>
>	> > One question for the list: in JOSM it seems that if raw gps mode
>is used
>	> > for an OSM download, that all points in view are treated as
being
>a
>	> > single track, based on sequential time stamp?  The result being
>that
>	> > relatively random straight segments appear just because there
>happen to
>	> > be some track points in view?  The manual doesn't really say.
>	>
>	> The traces downloaded from the server are just dots on a map
>nothing
>	> more. As far as I can remmeber they have no metadata.
>	>
>	> You should always create OSM data layers from a GPX file you
>yourself
>	> have created. Never from traces that is downloaded from the
server.
>	> And I'm not quite sure why it's not strictly verboten. Imi?
>	>
>
>
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