[Talk-us] script for adding layer=1 to bridges

Bill Ricker bill.n1vux at gmail.com
Thu Jan 28 02:49:57 GMT 2010


On Wed, Jan 27, 2010 at 8:47 PM, David ``Smith'' <vidthekid at gmail.com>wrote:

> Since some people consider
> the entire "layer" tag to be "tagging for the renderer" these people
> probably don't think it's important to add thorough layer information;
>

I would agree with your disagreement with such people. But I understand
their confusion. The *naming* of layer=* is unfortunately renderish, but it
carries real meaning beyond the oldschool mapmakers' plate masks. I would
wish the tag:layer had been more abstractly named tag:level. ah well.

I would also prefer real altitudes on all points rather than ordinal
relative levels (whether misnamed layer or not), but that's a bit of an ask.
And would cause semantic problems when ways become buildings (foundation or
roof elevation? include vertical segments?).


Ordering of the bridges in
http://www.stockphotopro.com/photo-thumbs-2/stockphotopro_33168BXD_no_title.jpgfrom
top-most to bottom-most is Data.

Likewise ordering of tunnel ramps weaving out of our Big Dig is Data.

It is DATA that a Transit line is in a uncovered ditch even when it's not
under a bridge.

Some non-rendering data-using software (or a person using data access) will
want to know up from down.
Silly example -- I could write a script to find examples of various
topological knots in the interchange ramp network, and which is under or
over at a crossing is critical.
Truck routing really need to know headroom at each underpass too, but we
don't have that usually.


-- 
Bill
n1vux at arrl.net bill.n1vux at gmail.com
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