[Tagging] Harmonising source tag values.

Tom Pfeifer t.pfeifer at computer.org
Wed Feb 8 09:22:44 UTC 2017


On 08.02.2017 02:47, Warin wrote:
> One mapper has taken on themselves to 'harmonise' some local source tag
> values.
>  .. the major example would be Bing, bing, BING, bing yyyy and bing yyyy

It is not possible to normalise them once you go beyond the simple 
example of Bing, and when you combine different sources in quality mapping.

> But I would see no point in it.

Neither do I. They are a descriptive text. Anybody who changes them 
without touching other data does not compress, he inflates the data by 
increasing version count.

On 08.02.2017 04:10, Tod Fitch wrote:
 > Is there any reason to use a source tag now that comments are required
 > on commits/edits?

Well more precisely it should not be the changeset comment, it should be 
the source=* tag in the changeset as opposed to the source=* tag on an 
individual object.

BTW, a source:FACT=* tag on a specific object is still useful, in 
particular when that source is different from the surrounding, such a 
geometry of a new building derived from GPS triangulation instead of 
aerial imagery. Thus I disagree with the wiki editor (9 Apr 2016) who 
called them 'historic'.

Back to the normalisation question, the source becomes complex nowadays. 
In Berlin we are fortunate that we are allowed to use the geo-portal of 
the local authority if we attribute them correctly. That portal has 
plenty of layers and a new aerial picture every year. Thus a typical 
source tag when I align a street and add some turn:lanes looks as follows:

source=local ground survey; Geoportal Berlin (DOP 2011+2016); mapillary

because I had seen the street with my eyes, I used the Digital 
Orthophoto (DOP) from the portal and compared different years, and used 
somebody's mapillary sequence to verify the turn:lanes. Similarly I 
might add the cadastre layer I am allowed to use.

Thus by comparing these different sources I am able to spot mistakes 
that are present in the official data.

tom



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