[OSM-talk] Is *just* tracing useful?

Dave Stubbs osm.list at randomjunk.co.uk
Fri Sep 7 09:43:35 BST 2007


On 07/09/07, David Groom <reviews at pacific-rim.net> wrote:

> > ----- Original Message -----
> > From: "Tom Chance" <tom at acrewoods.net>
> > To: <talk at openstreetmap.org>
> > Sent: Friday, September 07, 2007 12:26 AM
> > Subject: Re: [OSM-talk] Is *just* tracing useful?
> >
> >
> > On Friday 07 September 2007 00:08:30 Dave Stubbs wrote:
> >> Now my question is this: is this tracing actually useful?
> >>
> >> From my mapping perspective:
> >> - it makes it much harder to see what needs doing
> >> - when loaded onto my GPS the traced stuff becomes very difficult to
> >> distinguish, so it takes me longer and I also miss stuff because I
> assume
> >> it's been done.
> >> - entering the data takes longer because I have to fix all the oneway
> >> streets, and the ways that don't follow the roads, the ways that aren't
> >> roads, and all the bits that were missed anyway... it's much quicker to
>
> >> generate from scratch correctly
> >>
> >> In other words, I'd rather people didn't do it!
> >
> > I concur, in the area I've been mapping I usually end up spending more
> > time
> > deleting old segments and waysthan I do putting mine in from scratch.
> > Unless
> > you've been there you just don't know what the roads are like.
> >
>
> I disagree entirely.
>
> 1) there are areas of the world in which we will find it very hard to get
> complete coverage unless we use Yahoo imagery.  Ok, so we may at this
> stage
> only have the road layout and not the names, but it's better than nothing.
> Furthermore I've mapped large areas using Yahoo imagery, and then found
> other users have gone back and annotated the roads with names etc.  These
> people did not draw the road in the first place, and so the areas would
> still be blank



I have a horrible feeling the person who traced what I did will have the
same thought.


2) Say I've mapped an area, using GPS, add it to OSM, then look at Yahoo
> imagery and note I've missed off a few roads. Are you really suggesting I
> don't add them in just because I don't have a GPS trace for them?  I
> thought
> we were aiming for a complete map.



Well, hopefully you'll go back and fix them at some point. We're aiming for
a complete map, the question here is whether an unnamed street which has
just been traced constitutes mapping. It certainly couldn't be considered
'complete'


Toms comment about deleting old segments and ways is equally applicable to
> ways and segmnets added using GPS traces, where the person adding them has
> been less than meticulous in (a) tracing accurately over a GPS track, (b)
> actually making segments into ways (c) annotating those ways correctly.
> The
> complaint relates to inaccurate mapping skills by the user, and not the
> tools the user is using.
>
> With careful use of the Yahoo imagery it is possible to make a very
> educated
> guess about what it is you are mapping. In my experience the majority of
> mapping time is taken by defining the route of a road / path, and whether
> this is done by tracing a GPS track, or tracing from Yahoo is irrelevant.
> Particularly with the tools in JOSM it is easy to split or combine ways,
> so
> if the initial mapping via Yahoo is not accurate then things can be easily
> corrected.



I agree it is completely irrelevant whether the tracing was done with Yahoo
or GPS. Actually the problem of people tracing GPS was a lot worse because
they didn't have a clue what the GPS trace represented... I had to clear up
a pile of segmenting someone had done of what was clearly an insane trace
from a GPS without a proper lock.

I can also correct stuff. Unfortunately I can't do it very effectively in
Potlatch (it isn't designed for that purpose), which makes it slightly
tricky for me to use the Yahoo imagery in my mapping. Basically it's not so
much a question of whether I /can/, but that it takes about twice as long.


David
>
> > I'm sure some people do it with the intention of then visiting the area,
>
> > so it
> > can't all be bad. But where I've been working it looks like people have
> > just
> > randomly added odd bits of roads, parks, etc.
>
> So there are random parks, so what?  Surely its better than a whole load
> of
> white space on the map?  I'll hold my hand up here and admit I've added
> loads of woodland from the Yahoo imagery, I'm never going to walk around
> the
> boundary of those woods, same with the parks, beaches, and the coastline
> I've corrected using Yahoo imagery.
>
> Complain about inaccurate mapping if you like, but don't single out one
> particular method for complaint!



The problem is that the method is by far the most accessible to edit (thank
you Potlatch :-) ).
I'm all for tracing things it's unreasonable to do otherwise.. ie: walking
round boundaries is a waste of time mostly... just trace them. But the same
does not go for roads. I don't care whether there is a GPS trace or not...
there's a fairly large part of London where a GPS is completely useless.

This is basically the question: Is it better than a whole load of white
space on the map?
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