[Talk-GB] Re-mapping : Are these two ways both valid ?

[woll]

I don't really have any LEGAL opinion/knowledge to answer your question with,
but here is my experience:

When I first started remapping, I took your option 1 (delete the feature and
re-create it) because I felt that that option would ensure that no non-odbl
tainting could happen. I only added tags that I could get independently from
odbl-compatible sources, or from existing knowledge (so some tags may have
not been 'transferred' onto the new version). To 'transfer' the maximum
number of tags, you need to look at the history in detail, to see which tags
are from users who have agreed to the CTs (if you can't 'transfer' the tags
from your own knowledge/odbl-compatible sources. 

To find non-odbl tainted data, I used:
http://cleanmap.poole.ch/
the licence layer on the OSMI at tools.geofabrik.de/osmi
and the licence highlighting of Potlatch.

As I progressed, I started do a stricter version of your option 2, by
investigating the features in more detail, mainly using the info provided
by:
http://osm.mapki.com/history/
that shows which tags/features are non-odbl tainted.

My stricter criteria for option 2 is  "NO data remains from non-agreers"
(not your "enough has been done by other licence-accepting contributors that
the feature no longer belongs to the original contributor").

In a lot of the cases where I was working, I found various situations like:
a) All the original nodes of the feature (from users not agreeing to the
CTs) had been deleted (and new ones added)
b) The only tags remaining from users who have not agreed to the CTs were
factual tags like the name of the road or the number of the road, that I
could easily get from odbl-compatible sources/knowledge.
c) All the original nodes had been moved by agreeing users (presumably by
aligning to aerial imagery/more accurate GPS tracks)
d) The only thing remaining from non-agreers was a small percentage of the
nodes in a way, and those nodes were not very accurately positioned.

When I found that ALL the non-odbl data had actually been replaced, then I
added "odbl=clean" (this last step might not be necessary in some cases,
because the tools could probably be extended to work this out for themselves
if they looked at the history in detail, but I did it to be safe).

When I found that the only non-odbl data remaining, could be got from
odbl-compatible sources/knowledge, I re-added it, and added "odbl=clean"
(the last bit is necessary, because even though I deleted and re-added the
tags, the tools can't tell that I actually did that (because the tags are
exactly the same).

If there were any non-odbl tags remaining that I couldn't get from
odbl-compatible sources/knowledge then I deleted them. This was very rare
for the features I was looking at, and was only 'irrelevant' things (e.g.
not very useful notes). I probably didn't need to do this, as for most
situations, I expect that the final process that will transfer the data
would automatically delete these tags (it wouldn't delete a way just because
there was just 1 non-odbl tag remaining, it would just delete that tag and
keep everything else. however adding the "odbl=clean" tag means that the
existing visualisation tools will then display things correctly).

If the only non-odbl data remaining was a small percentage of the nodes in a
way, I deleted/replaced them with more accurate ones based on more accurate
GPS tracks or imagery (and normally took the opportunity to add more nodes
for more accuracy).

So, option 2 is not really "less work" - it actually takes quite a long time
to look at the history in detail (and then drilling down to look at all the
nodes of a way). 
Option 1 is not necessarily "more work" either: Unless you can easily get
all of the tags from odbl-compatible sources/knowledge (or you don't care if
you don't 'transfer' all of the existing tags) then you also need to look at
the history in detail.

To specifically answer your questions: 
Your option 1 is obviously "legal/ethical" (you're deleting everything and
recreating it)
I personally would not be happy doing your option 2 (which would vary on
everyone's different interpretation of "enough"). The re-mapping I have done
is stricter than that and ensures that there is no tainting remaining (but
that means that option 2 is not necessarily "less work" than option 1).

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