[OSM-talk] New Proposed Feature: Tagging the age and duration of existence of features

[Lester Caine]

OJ W wrote:
> start_date=, end_date=
> 
> http://wiki.openstreetmap.org/wiki/Map_Features#Properties
> 
> http://osmdoc.com/en/tag/start_date/
> 
> http://osmdoc.com/en/tag/end_date/
> 
> maybe someone could create the tag pages for those on wiki?
> 
> 2009/5/22 Peter Dörrie <peter.doerrie at googlemail.com>:
>> Hi everybody,
>>
>> I made a proposal for tagging "the 4th dimension". Hope you like it ;)
>>
>> http://wiki.openstreetmap.org/wiki/Proposed_features/4th_Dimension

There are a couple of things here that need discussing, but hopefully 
that can be a quick discussion. MANY of the features on the map can be 
identified with a 'start_date' and it would be nice to have that 
information. Lots of new roads are being built, and many historic 
locations have a construction date.

The problem comes with 'end_date', and since in some areas roads ARE 
being destroyed, are they removed from the map or CAN they be left with 
an end_date and features which have an end_date earlier than the current 
date are ignored? ( I'm thinking of the 2012 Olympic site which has 
re-routed many roads? )

The actual content of a date is a major point of discussion, but for the 
time being I would propose sticking with a simple ISO date format. The 
discussion on historic date formats has been going on for years now on 
the genealogical lists without agreement. Just consider where a 
start_date is between two known dates. i.e. a feature is absent on a map 
of 1945 but present in the 1955 map - so you end up with a more complex 
start_date entry ... and which calendar was used to provide the date ;)

( start_date and end_date were I think added for things like festivals 
and other transitory map information, so it may be appropriate to 
redefine them as constructed_date and demolished_date to distinguish 
historic data from transitory data ? )

-- 
Lester Caine - G8HFL
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