Re: Tracing items.

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80n
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Re: Tracing items.

80n
On Thu, Jun 5, 2008 at 5:38 AM, <[hidden email]> wrote:
Hi All,

Just a general comment and a couple of suggestions.

Having been adding items into osm for the last year I've noticed people
spending a lot of time tracing roads from landsat, yahoo, etc.

While this is admirable work is this really a useful exercise.  Someone
will eventually drive along this road with a gps upload it and then erase
the traced road.

Or worse still will not bother to drive down that road as it's already in
osm and not tagged as survey and therefore not sure should they replace
it.  So it never gets surveyed accurately.

So my suggestion is instead of tracing roads, trace things that can not be
easily surveyed.  eg railway lines, rivers, powerlines.

IMHO Yahoo tracers should focus on lakes (and other bodies of water), parks and buildings.  After that maybe roads with no public access.  Tracing public roads should be a last resort, they'll get done much sooner using GPS if they are not already traced from Yahoo.

I'm not saying that Yahoo tracers should not do roads, but please do lakes and buildings and stuff first.  Give the GPS guys a chance to do the roads.  It's a big planet we are not going to run out of unmapped space any time soon.

80n


 

Or fix the coastline.  There's still lots of areas where the coastline is
not accurate and needs to be fixed up.

Anyway just my 2c's.

Cheers
Ross



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Re: Tracing items.

Darrin Smith
On Thu, 5 Jun 2008 23:25:06 +0100
80n <[hidden email]> wrote:

> On Thu, Jun 5, 2008 at 5:38 AM, <[hidden email]> wrote:
>
> > Hi All,
> >
> > Just a general comment and a couple of suggestions.
> >
> > Having been adding items into osm for the last year I've noticed
> > people spending a lot of time tracing roads from landsat, yahoo,
> > etc.
> >
> > While this is admirable work is this really a useful exercise.
> > Someone will eventually drive along this road with a gps upload it
> > and then erase the traced road.
> >
> > Or worse still will not bother to drive down that road as it's
> > already in osm and not tagged as survey and therefore not sure
> > should they replace it.  So it never gets surveyed accurately.
> >
> > So my suggestion is instead of tracing roads, trace things that can
> > not be easily surveyed.  eg railway lines, rivers, powerlines.
> >
>
> IMHO Yahoo tracers should focus on lakes (and other bodies of water),
> parks and buildings.  After that maybe roads with no public access.
> Tracing public roads should be a last resort, they'll get done much
> sooner using GPS if they are not already traced from Yahoo.
>
> I'm not saying that Yahoo tracers should not do roads, but please do
> lakes and buildings and stuff first.  Give the GPS guys a chance to
> do the roads. It's a big planet we are not going to run out of
> unmapped space any time soon.

If that's the case, why be picky about what anybody maps? Let those who
want to contribute in their own way do it. It may get them traced
quicker leaving them blank, but it gets them MAPPED quicker if someone
does them via Yahoo/etc. By you argument you'd be happy to sit there
with huge empty swaths of map whilst someone wastes time doodling
buildings (what relevance those have on a street map is debatable,
although they do look very cool) and not adding useful navigational
data to the map.

It's trivial to find out if an area hasn't been gps tracked by firing
up josm and searching for roads without the source:survey tag if you
want to GPS map an area.
--

=b

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Liz
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Re: Tracing items.

Liz
In reply to this post by 80n
On Fri, 6 Jun 2008, 80n wrote:
> I'm not saying that Yahoo tracers should not do roads, but please do lakes
> and buildings and stuff first.  Give the GPS guys a chance to do the roads.
> It's a big planet we are not going to run out of unmapped space any time
> soon.
>
> 80n

This weekend I'm going to Darwin (plane, car not fixed yet) and that city has
a lot of streets done by Yahoo, no names, not much detail.
So on foot, should I be photographing all the street signs or walking up and
down every street trying to get a GPS trace?

My main technical interest is whether the work in Darwin requires redoing as
there has not been an adequate georeferencing of the photogrammetry.

(for you lot - are the streets in the right place on the ground or are we
several hundred metres out overall)

I can't see a problem with anyone adding from any source PROVIDED it is
IDENTIFIED
How else will we get Darwin mapped?

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Re: Tracing items.

Kim Hawtin-2
In reply to this post by 80n
Darrin Smith wrote:
>> So my suggestion is instead of tracing roads, trace things that can
>> not be easily surveyed.  eg railway lines, rivers, powerlines.
>
> Railway lines are easy to survey, catch a train ;)

there are a bunch of railway lines around here that are not for
passenger trains. so i have walked a couple. i need a handheld
gps instead of the big laptop and usb dongle gps =) would make
this stuff a whole lot easier.

power lines are tricky, they are not really public land, AFAICT.

cheers,

kim
--
Operating Systems, Services and Operations
Information Technology Services, The University of Adelaide
[hidden email]

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Re: Tracing items.

Ross Scanlon
In reply to this post by 80n
> And if someone enjoys tracing roads or some other feature exclusively
> are we to tell them to go away because it's not our idea of the best
> way to spend their time on OSM?

Missed the point of my suggestion totally didn't you.  I am not saying
don't do it just that if you want to improve the whole map in osm then
here are some things that will help to do that.

OSM is not just about streets/roads/highways.

It's about the whole map.  Look at some of the parts of UK and Europe.
There's now even proposals to include the street numbers.

All things that add to the navigation assistance available.

As to using josm etc that's fine if I've got the laptop running or sitting
at home at the desktop connected to the internet.

But when I'm on the road and I've got gpsdrive with mapnik running and the
osm data is from last thursday and I'm not connected to the internet, I
can't tell if the road was traced from Yahoo etc or from a gps upload.

Cheers
Ross



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Re: Tracing items.

Ian Sergeant
In reply to this post by Liz
Liz <[hidden email]> wrote:

> My main technical interest is whether the work in Darwin requires redoing
as
> there has not been an adequate georeferencing of the photogrammetry.

> (for you lot - are the streets in the right place on the ground or are we

> several hundred metres out overall)
>
> I can't see a problem with anyone adding from any source PROVIDED it is
> IDENTIFIED
> How else will we get Darwin mapped?

I was in Darwin last year sometime, and I realigned and named some of the
main roads that were traced from yahoo imagery.

My observations then, and this may have changed since, were that

* There were many road features on the map that were different to on the
ground
* High-res imagery was generally well aligned to the GPS tracks, like it is
in most of Sydney
* The satellite imagery out of Darwin in the NT is clear, but considerably
out relative to the GPS trace (I realigned the Stuart Highway from Darwin
to Katherine).

All the roads that I aligned to the GPS data have been noted as
source:survey.  I don't know if I uploaded all of the traces though.

Ian.


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Re: Tracing items.

Andrew Loughhead
In reply to this post by Ross Scanlon
[hidden email] wrote:
>> And if someone enjoys tracing roads or some other feature exclusively
>> are we to tell them to go away because it's not our idea of the best
>> way to spend their time on OSM?
>>    
>
> Missed the point of my suggestion totally didn't you.  I am not saying
> don't do it just that if you want to improve the whole map in osm then
> here are some things that will help to do that.
>  
Good grief.  Can we please all calm down?  Really there is no need for
such aggressive emails here.

OSM is somewhat like a wiki. In a wiki people will contribute in
different ways, basically scratching their own itch.

I did most of the inner north Canberra suburbs with GPS.  When the yahoo
imagery became available I was able to compare the two.  Yahoo was fine
enough for positional accuracy, certainly within the error margin of an
average consumer GPS in stream mode.

We had a baby. At that point my ability to find time to ride or drive
around getting GPS traces vanished. But I felt I could still contribute,
using Yahoo imagery.

I traced quite a bit of inner Canberra from Yahoo.  I am confident that
the georeference of the imagery around here is fine, and I am familiar
enough with the areas traced that I doubt I made any more errors than
gps mapping would make.  I am also confident that my tracing has
produced better *shape* in the roads than most mapping in OSM, some of
which looks a bit like join-the-dots.

And thats the thing.  I liked tracing, and I liked getting the circles
and curves of older Canberra to be just right. Yahoo was a great way to
do it, and I think arguably much better than GPS, for shape.  Yahoo
imagery is a little out of date sometimes, where roads have been
realigned, but I live here, and drive through these areas, and I doubt I
have traced any errors.  Overall, I got to scratch my itch.

Then I found some of my local co-mappers writing negative emails and
diary entries, somewhat like the opening of this thread, containing
similar statements about Yahoo, and others frankly I don't understand,
to the effect that "it all has to be re-done anyway".  I *think* that
was because those areas needed to be visited again to get names and
other features.  The time consuming phase of doing really nice shape
didn't need to be done again, but that wasn't *their* itch, so they I
guess they didn't value that.  Their itch was having many names and many
features.

So while I think I understand and value the contributions of my local
fellow mappers, who have done a fantastic job of collecting other parts
of Canberra, and of filling in many more feature types and names than I
would ever have been bothered to do, I don't feel like my own
contribution was valued.  My enthusiasm dried up and I don't invest time
in OSM now.

I think Darrin made a perfectly fair point: "Let those who want to
contribute in their own way do it."  Unless people do things that are
substantively damaging to OSM, then whatever they want to contribute
should be valued.  Otherwise contributors are just driven away by those
who think they understand everything and that their view is the only
valid one.

I think that not understanding that someone elses motivation or itch, is
different from your own, is missing the point.

cheers
Andrew.


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Re: Tracing items.

Jim Croft
On Fri, Jun 6, 2008 at 11:34 PM, Andrew Loughhead
<[hidden email]> wrote:
> [hidden email] wrote:
> Good grief.  Can we please all calm down?  Really there is no need for
> such aggressive emails here.

Aggressive?  You have obviously never witnessed the mortal combat of a
real flame war.  This is nothing - just a bunch of pussies tugging at
a ball of string...  I have been on lists where there have been
threats of legal action and people have been excommunicated and banned
for life!   :)

> And thats the thing.  I liked tracing, and I liked getting the circles
> and curves of older Canberra to be just right. Yahoo was a great way to
> do it, and I think arguably much better than GPS, for shape.  Yahoo
> imagery is a little out of date sometimes, where roads have been
> realigned, but I live here, and drive through these areas, and I doubt I
> have traced any errors.  Overall, I got to scratch my itch.

At the foundation of this is the core of what OSM is - it is an Open
Street *Map*.   And maps are not reality; they are a functional
representation.  If we think we are building a community GIS then we
totally are using the wrong tool set.  For a street map it does not
really matter that that every wrinkle is accurate and precise down to
the finest resolution (the mere fact we fatten streets to accommodate
their names ensures perpetual inaccuracy); only that the
representation is meaningful.  The extreme of this is the London
Underground map - totally inaccurate spatially, but absolutely
meaningful (I never get bored on the Underground because I spend the
whole time reflecting on the transcendent zen-like reality, yet
unreality, of this map).

I lurk (also in inner north Canberra) on OSM not just because I like
the visualization of spatial relationships, but because I find the
sociology of a community building something fascinating (in the same
way I am mesmerized by Wikipedia, not by its content and its coverage,
but by the fact it exists at all and seems to work).

If I want a pretty, well rendered, well registered and authoritative
local map I use things like ACT Locate and ACTMAPi which are built on
a grunty GIS; but I I want to feel good, I delve onto OSM.  And the
feeling good has nothing to do with the quality, coverage and
presentation of the map, but with the fact that it exists at all and
seems to work.

An interesting about community information management projects, and I
am involved in and contribute to a number, is that they never go
exactly in the direction you want them to, but with a bit of effort
you can sometimes influence the direction in which they are pointed.
This is pretty confronting for control freaks, but fascinating to part
of and witness in action...  :)

jim

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Jim Croft
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"I don't know why we are here, but I'm pretty sure that it is not in
order to enjoy ourselves."
- Ludwig Wittgenstein, philosopher (1889-1951)

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