[OSM-talk] Why place matters, slides from Vanessa Lawrence talk

[Andy Robinson (blackadder)]

David Earl wrote:
>Sent: 11 January 2008 11:22 AM
>To: Jon Burgess
>Cc: talk at openstreetmap.org
>Subject: Re: [OSM-talk] Why place matters, slides from Vanessa Lawrence
>talk
>
>On 11/01/2008 00:55, Jon Burgess wrote:
>> On Fri, 2008-01-11 at 00:09 +0000, martin dodge wrote:
>>> Hi,
>>>
>>> Just found an interesting set of slides of a talk by Vanessa Lawrence,
>OS
>>> http://www.w3.org/2007/06/eGov-dc/presentations/VL_why_place_matters.pdf
>>> with some prominent mentions for OSM. I particularly liked slide 46
>>>
>>
>> The map in his screenshot must be from quite some time ago. The same
>> area of central London now has considerably more data
>
>I think that misses the point. There are still many, many other areas
>where there is still just as little data, but that's not the point either.
>
>The key thing is 'how do you know?'. If you look at the current coverage
>of that London area, it probably looks quite convincing now, whereas in
>her slide it was obviously incomplete, yet I bet it isn't (in fact, I
>know it isn't - there are numerous missing streets in the densely mapped
>central London). How would I know this? How do I know whether I can
>trust this map or not? (*)
>
>This was and remains one of my key concerns about OSM as a project. I've
>said before and I'll say again: we need a way of asserting "this area is
>complete" (for one or more definitions of completeness).
>

I totally agree with your points David and I've had them voiced directly to
me by people who have tried the default map render for the first time
(incidentally the name finder came in for some flak due to its data not
matching the map content - we need to be careful there too). However I'm
less concerned about validity provided that we don't try to oversell our
mapping as "complete" before its been validated. The only way that we are
going to individually or collectively state the completeness of a specific
area is to carry out a verification process. It doesn't have to be done by
third parties or even different contributors but it does need to be done by
someone. I have started to do it for Sutton Coldfield and it can only be
achieved on foot. I've been surprised just how much extra data can be added
just by taking a little time over each street and I've found a few features
that really should have been on the map already, despite being less than
half a mile from my home.

I'm not suggesting for one minute that the verification task is easy or
quick, but it is necessary.

We need a simple tag to display verification, perhaps the username and a
date, say verification=blackadder_20080111 or similar. That doesn't stop
someone falsifying validation but then I don't really think falsification is
in the OSM mindset to begin with and so probably not something to be really
concerned about for the majority of the data. User feedback would in my
expectation continue to spot problem areas if they crop up.

>Incidentally, this is exacerbated by the lazy rendering rule for Mapnik
>- I was puzzled when someone said to me the other day "why is this
>housing estate not connected to the rest of the road network?". It was;
>but adjacent Mapnik tiles were inconsistent (both laterally and by zoom
>level - and this wasn't a recently mapped area). You may not think this
>matters, but I think this is a public face and it causes further
>confusion and mistrust.
>
>David
>
>
>(* And how would I know how to fill in the gaps if I was there without
>revisiting every already mapped street?).
>


Cheers

Andy