[Tagging] Feature proposal - Power transmission refinement - RFC 2

Jesse Crawford jesse at jbcrawford.us
Wed Jul 9 20:30:26 UTC 2014


On Wed, Jul 9, 2014 at 1:30 PM, Ole Nielsen <on-osm at xs4all.nl> wrote:

> 1) This proposal requires a voltage tag to distinguish "big" and "small"
> power lines. If mappers don't add a voltage tag then it's probably because
> they don't know the voltage and this information is often difficult to get
> hand on. However, they can mostly figure out whether it is a "major" or a
> "minor" power line looking at the towers/poles and use either "line" or
> "minor line" appropriately. With only "power=line" as main tag and not
> knowing the voltage they can't add this information anymore.
>
> 2) The proposal will require renderers and other consumers to evaluate the
> voltage tag if they want to distinguish between major and minor lines. This
> can however be a rather complex task since the voltage tag values are not
> always simple numerical values as required to perform simple comparisons.
> In the case where two voltage separated by a semicolon are specified more
> complex processing using regular expressions etc is required. I have the
> feeling that the Carto stylesheet maintainers won't be eager to implement
> that (if supported by Carto at all).
>
> The result of deprecating "minor_line" will effectively be a loss of
> information in the database and in inferior rendering of power lines (400
> kilovolt lines and 400 volt lines will be rendered the same way!)
>

As an additional support for this perspective, in my area (where I am able
to access detailed utility maps because they are publicly owned and the
local authority is unusually thorough with its website), lines at 13.2kv
and 115kv are visually indistinguishable, but a map renderer might be
tempted to show them differently because they are "distribution" vs
"transmission" levels. However, when the 115kv lines leave the city they go
from wood poles to metal ones without an actual change in voltage. Further,
at least in my experience this information is usually not at all easy to
access in the US. In many areas determining voltages for transmission lines
would probably require visits to the offices of multiple local planning
authorities, photocopy fees, and in general a great deal of hassle.

I absolutely support marking voltage (and also capacity if possible)
because I find this to be interesting, but it shouldn't be the basis for
rendering, as it does not reliably predict visual appearance (what is on
the ground) and it is not easy to determine.

Jesse B. Crawford
Student, Information Technology
New Mexico Inst. of Mining & Tech

jcrawford at cs.nmt.edu | jesse at jbcrawford.us
http://cs.nmt.edu/~jcrawford | http://jbcrawford.us
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