[OSM-talk] GPS scribble in JOSM

Jon Burgess jburgess at uklinux.net
Mon Sep 4 19:19:39 BST 2006


On Mon, 2006-09-04 at 18:52 +0100, Ed Davies wrote:
> I've turned off all of the layers except for the downloaded
> GPS tracklogs.  I've zoomed out slightly relative to the
> original block downloaded.
> 
> Any idea what's going on?
> 
> I have a theory/hunch/suspicion: if two tracklogs were
> recorded at the same time could it be that OSM or JOSM
> is taking the points in time order and therefore jumping
> backwards and forwards between the two logs?
> 

Sounds likely to me. Try Edit->Preferences and disabling the "Draw lines
between raw GPS points".

How did you download the GPX traces? did you download the files
individually or did you use the "download raw GPS" option?

I see the same thing in JOSM if I have the draw lines option enabled
when I have a layer with raw GPS visible. I think the raw GPS data is
probably just a list of all points within the bounding box in a pseudo
random order so drawing lines between the points makes no sense. 

There is a chance that this worked differently before the recent
algorithm changes to speed up the database access. I don't think the API
makes any guarantees though that the nodes will be in any kind of order,
if it worked better before, it was probably by luck.

JOSM probably shouldn't even try drawing lines between the nodes for raw
GPS data.

	Jon






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