[OSM-talk] Source as attribute of object or changeset ? [was: Re: Import guidelines & OSMF/DWG governance]

[Jaakko Helleranta.com]

"Have such schemes been proposed before ?"

Not sure about that.

But this is logical and feasible _if_ all added/edited objects in a changeset had/have the same source.

I can only say for sure about my own mapping: It would be almost always impossible for me -- except when tracing in areas I've never been to. Other than that my sources are a colorful mix of: survey, knowledge, GPS, GPS-aligned imagery, imageries (Bing, Google 2010 in Haiti, etc). This in a way that is totally impossible to tag to changeset.

Other than the showstopper above I also find the source tags of/on objects quite often _very_ useful for estimating the accuracy/reliability of the data in question.
It also follows the data through extracts and various outside-the-OSM-universe use, which I think is a good idea.

So, I see no good reason for tagging source to changeset (only). 

Cheers,
-Jaakko

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-----Original Message-----
From: Jean-Marc Liotier <jm at liotier.org>
Date: Wed, 19 Sep 2012 16:20:29 
To: Martin Koppenhoefer<dieterdreist at gmail.com>
Cc: <talk at openstreetmap.org>
Subject: [OSM-talk] Source as attribute of object or changeset ? [was: Re:
 Import guidelines & OSMF/DWG governance]

On 19/09/2012 15:58, Martin Koppenhoefer wrote:
> It seems that you generally apply the source-tag to the osm object 
> instead of the changeset comment, but I'd propose to do it the other 
> way round. There are already tens of millions of objects in the db 
> with related source-tags 
> http://taginfo.openstreetmap.org/search?q=source+%3D+cadastre-dgi-fr 
> and putting it into the changeset comment could possibly reduce the 
> size of the objects tables in the db. This leads also to another 
> question: how should a mapper deal with these source tags when he 
> applies modifications to the object?
I suggest inheritance of source from the changeset, unless overridden by 
the object's source tag : let the changeset have an optional source 
attribute that applies to all the changeset's objects that do not have a 
source tag.

Editors such as JOSM could display a virtual source tag that contains 
information from its changeset's source attribute if it is present.

Have such schemes been proposed before ?


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