[Tagging] RFC - Key: spacing=*

[Peter Elderson]

Hi, I'm new on this list. Please correct me (be gentle...)  if I breach any
protocols or agreements about how to start issues or proposals

I am exploring the possibility of proposing a new key for spacing of more
or less regularly distributed objects along a way or over an area.
This is part of a rendering proposal for natural=tree_row, but it clearly
has potential for wider use.
That's why it's proposed to be a general purpose dimensioning key, such as
width, length, heigt and ele.
It is applicable to ways and areas with a regular or repetetive pattern,
such as barriers, rows of trees, and areas such as orchards, forest, hedges.
I've come across many posts where taggers would like to indicate density,
or indicatiion of the number of trees involved. Low spacing  is the same as
high density and reversely related to number of trees, so this key
accommodates those wishes.

The aim is to provide renderers with a means for adaptive rendering, e.g.
very dense forest vs open forest, or an almost hedge-like tree_row vs a row
of poplars spaced on average every 100 m along a motorway over a length of
10 Km.
It's explicitly intended as a non-exact dimension. It does not indicate
exact positions. The renderers will be asked to translate the value into a
symbolic rendering, eg more or fewer tree icons rostered over a forest or

I'm guessing the renderers would translate the value to a limited scale of
3 - 5 degrees of density (high, average, low or very dense, dense, average,
low density, very low density) and apply that to the spacing of symbolic
trees over a forest or orchard.

spacing=*
values:
- an integer value specifying average or estimated distance between objects
- optionally followed by a space and a unit, default is m
- I'm thinking of adding a special value to indicate that the exact
location of the objects is given by the nodes mapped on the way. The value
could be 0 or 'free'or 'nodes'.


The last option is extra, it's added for conveniance of mapping tree_rows
or similar arrays of objects, and requires some explanation.

spacing=nodes enables the renderer to represent objects on the map exactly
where they are on the ground. The advantage over mapping and rendering
individual trees a natural=tree is

a. mapping and tagging a long tree row with exact locations would be much
quicker this way than mapping  individual trees. The tags of the tree_row
can be applied to all the nodes.

b. the rendering can be different from individual trees, more adapted to
the appearance of trees in a row as seen on the ground. A row of trees
resembles a row of dark or brown poles. The crowns are much less important.
But design is up to the renderer; the tags and nodes in this case represent
actual data.

-- 
Peter Elderson
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