[OSM-talk] 'Allowed data'

[Russ Nelson]

Lester Caine writes:
 > Martin Koppenhoefer wrote:
 > > 2013/12/7 Lester Caine <lester at lsces.co.uk <mailto:lester at lsces.co.uk>>
 > >
 > > Delete is simply not a valid concept unless the object never
 > > existed in the first place?

And maybe not even then. I've been working on the Dunderberg Spiral
Railway, which is an unfinished railroad built on the side of
Dunderberg Mountain just south of Bear Mountain Bridge on the Hudson.

The most awesome thing is that you can see a BUNCH of the railbed on
the Bing Aerial photos, if you know what you're looking at and for.

About 65% of the railway was graded before they gave up. The
difficulty is making sense of the bits that were actually constructed
-- how do they fit into the design of a continuous ten mile loop of
railroad going up in two inclines, then curving around the mountain
twice, then back and forth four times. Without mapping the unbilt
portions, it's quite difficult to make sense of the bits and pieces of
railbed that were built.

The only difficulty is how to tag an unfinished railway. I tried
railway=unfinished, but NE2 helpfully changed it all to railway=abandoned.

 > > While I find this concept appealing at first glance, it would
 > > raise complexity much more if we not only had present but also
 > > past objects in the db.

There is room for a LOT of things in the database that you don't want
to see when you're editing. For example, power lines, or
boundaries. Sounds like you want to filter out anything with an
end_date tag.

 > Which is exactly why the 'start_date' and 'end_date' become
 > important elements. Rather than simply wiping those historic layers
 > they get an end date, and the editors simply ignore them unless one
 > has enabled a date range. This then replaces simply deleting
 > perfectly good data and instead hides it away properly. The
 > original proposal was that this data would get moved off to OHM,
 > but that simply does not work when the bulk of the surrounding data
 > is still required from the OSM version.

Yeah, OHM doesn't work, not when railbeds get reused as hiking trails,
as some of the Dunderberg railbeds have been, and when the trail gets
rerouted onto railbed, as the R-D trail has been. I was looking for
railbed off the trail, and found old Red Dot blazes instead.

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