[OSM-talk] Historic Mapping needs help Now!

[Roy Wallace]

On Wed, Aug 19, 2009 at 11:07 AM, Stephen Hope<slhope at gmail.com> wrote:
> I am hoping in a couple of weeks to map the grounds at a festival that
> occurs yearly in the same spot. This is not so much historical data,
> as data that's only true for three weeks a year. The rest of the time,
> it's just fields, with a few items (some toilets, etc) that stay in
> place year round.
>
> Would this come under historical mapping, or some other tagging scheme?

Good question. If you treated it as historical mapping, you would
create a duplicate set of nodes/ways/relations for each year, with
appropriate absolute start/end dates (for that year).

Is this satisfactory?

Actually, an alternative is to relax the definition of "start_date"
and "end_date" to be not just absolute times, but more flexible as
follows:

Think of a calendar application where you can define a meeting that is
"3 to 5 pm on Wednesdays in 2009" - this is not an 'absolute'
description of the time the meeting comes into and out of existence,
but nevertheless is sufficient to describe when the meeting exists.

Is this all we need for OSM, i.e., to be able to answer the question:
"given the start_date and end_date of this node/way, does it exist at
this particular time, x?"

On another note, I would propose using start_time and end_time rather
than *_date, because time (as a dimension of existence) is really what
we're talking about.