[Talk-GB] OpenKent, OSM coverage estimation

[TimSC]

On 07/06/11 14:37, Richard Fairhurst wrote:
> TimSC wrote:
>    
>> I think you miss my point. The datasets contain more than just their
>> postal address. If the licenses are compatible, we can mash up the data.
>>      
> You don't need to put stuff into OSM to make it mashable-uppable. Most
> competent licences will have a Collective Work/Database provision to
> enable this.
>    
While this this strictly true, it is sometimes hard to associate 
external records with specific OSM objects. Some importing of reference 
and ID numbers makes this easier.

And back to my original point, I am still not sure if under the new OSM 
license if I can mash up OSM data with, for example, OGL data as a 
"produced work". I think I remember you are in the camp that thinks 
there is no problem with that, legally speaking. But issues of license 
compatibility are probably best on the legal list anyway.

>> This implies I don't already, which is a false. (Otherwise, why are you
>> telling me I should?)
>>      
> Oh, cool. Sorry, I thought you were still using Yahoo imagery to trace
> places you'd never been. Glad you've stopped. :)
>    
Yeah I have reformed and seen the light. I now use Bing. :)

>> [...]
>> Any what if the government dataset is open and stomps on OSM's attempt?
>>      
> OS OpenData is easily the best free geodata available in the UK and I've
> just used it (in preference to OSM) to make a lovely paper map, but it
> hasn't killed OSM yet. :)
>    
Again, separate issue. Ok, contributors still contribute to OSM but how 
are we doing on users actually using OSM when it is incomplete compared 
to other data sets? Would we have more users if our coverage was better? 
I argue, yes of course.

> In a few cases, manually importing data can indeed be a useful tool. The
> high-resolution rivers and streams in VectorMap District are quite useful
> _if_ you know the stream is indeed there, which obviously VMD doesn't tell
> you.
You are referencing the common guideline that mappers should only edit 
areas they have been to. I don't follow that guideline blindly, as you 
pointed out. Steve Chilton and myself have traced many streams from 
decades old maps. We like to think we are improving OSM and no one has 
complained about a specific stream edit yet, as far as I am aware. I had 
a few (four or five) queries about specific roads but the questions are 
always requests for confirmation rather than demands to stop importing.

As far as I understand, your vision of a map which has only direct 
knowledge and survey would leave many countryside and mountainous areas 
very bare. You obviously consider this acceptable (and actually that 
view has some merit). Many tracing contributors don't. A near blank 
walking map is nearly useless - which is what would result, if we only 
have map data on OSM contributor accessible places.

I guess you already thought of all this, so time for me to shut up on 
that point!

>   It's not really any better than using a combination of aerial imagery
> and your own knowledge, but it can be useful, yes.
>    
(I feel like I am disagreeing with every point to make, but here goes!) 
I disagree. The quality of VMD is better than what I can produce using 
Bing - thanks to tree cover, or even GPS surveying with my consumer 
level gear. VMD is very detailed and precise (but not without errors, 
obviously).

> But this is pretty much only true where the data is impractical to survey
> yourself. The canonical example is: if you import a town's roads, you get
> a town's roads. If you survey a town's roads, you get a town's roads,
> footpaths, cycle routes, pubs, etc. etc.
I agree (yay!) and that a badly managed import can drive away people 
from improving it. I still feel this is more of an issue with tools and 
physiology than the data import itself. For example, if I see a bus 
stop, I normally think that "Naptan has imported that, I will ignore 
it." - this is not an ideal attitude but it frees time to map other 
things. However, if I could easily distinguish between unverified 
imported data and surveyor data, I might do more on bus stops. We would 
then have a dataset that is better than either a pure OSM surveyor set 
and the original naptan data. We need to ask "how do we make this 
possible?" and move beyond the answer "ban imports".

>   I'm sure there's been an example
> where an import has been significant in the success of OSM in the UK but
> I'm struggling to think of one. Maybe someone else can help?
>    
It depends on your definition of "import" (obviously). If you include 
tracing, I traced 90% of SE London and then Semantic Tourist used that 
in walking papers to survey it personally. Would that be an example? It 
also fits my vision of "import and improve".

I traced the buildings for my neighbourhood in Guildford and then used 
that as a basis to collect addresses? Any good?

 From the point of view of improving coverage, naptan was a success. It 
was a disaster in terms of avoiding duplicates.

It would be hard to argue that OS Opendata has not been an asset to 
OSM...? There are many country roads that are not sign posted but are in 
OS Locator - and now in OSM.

>> I am not advocating we
>> only import data either. A hybrid approach - import AND crowd source -
>> is better. If you want crowd sourced surveying only, I suggest you start
>> another project.
>>      
> Fortunately, I _like_ the licence that 23135 people have said they'll move
> their data to, and only 387 have said they won't (that's 98.4% vs 1.6%).
>    
Err, I am not sure how the relicensing is relevant to controlling 
imports? People still can trace NPE and 7th series OS and any PD source.

If you hope that relicensing will reduce the amount of OS Opendata, I 
think you might be disappointed. Many significant contributors have 
signed the CTs on the assumption that LWG will find a way to allow 
continued OS Opendata importing. [1][2]

> So I'm not planning to be one of the people moving to another project. :)
>    

If you are having a smirk that I am in the minority in the debate - 
strictly speaking I have not agreed or disagreed with the CTs yet! I 
didn't say move projects - I said start another. I know that sounds like 
nit picking but I am serious! - I already divide my time between several 
open data projects - and that was before the re-licensing issue. I don't 
think a monolithic map database is the way to go but I am not exactly 
quitting OSM!

Regard,

TimSC

[1] http://lists.openstreetmap.org/pipermail/talk-gb/2011-April/011476.html
[2] http://lists.openstreetmap.org/pipermail/talk-gb/2011-April/011489.html