[Tagging] Clarificarions for highway=speed_camera

[Nelson A. de Oliveira]

Sometimes some doubts about highway=speed_camera arise here in Brazil.

The most recent discussion is about:

1) In iD "speed camera" was translated as "speed sensor" in Portuguese
and some people are mapping where the ground sensor (which detects the
vehicle) is located at the road, instead understading and mapping it
as the camera device itself.

For me it's just necessary to fix the translation, but to solve this
doubt, "speed camera" means *only* the camera device?
ie, this device at the right side
https://wiki.openstreetmap.org/w/images/7/7c/Speed_camera.jpg

People usually understand it as an object that summarizes a group of
ground sensors + radar + camera.

2) For simplicity¹ people are mapping speed cameras as a node at the
highway. I won't discuss this here, but a related problem with this
is: they are starting to use the "direction" key to specify which side
the speed camera applies to, when used in a two-way street.
ie, direction=forward if the enforcement applies only to the same
direction as the highway way, direction=backward if it applies to the
opposite direction and direction=both, if the enforcement applies to
vehicles in both directions.

¹ simplicity = not knowing/wanting to use an enforcement relation

Their arguments in favor of using direction like this:
- it's simple to map (since people will not have to use an enforcement relation)
- it should work exactly like highway=stop's direction (where it
represents the way direction that the stop applies to)

But what I see:
- it is ambiguous: it means where the camera is pointing to or it
means the direction that it applies too?
- it changes the semantics of "direction"; ie, if we map a speed
camera with direction=forward meaning "the enforcement applies only to
the same direction of the way", then how we are going to represent the
direction the camera is pointing?
- we already have enforcement relations to represent the direction
that the enforcement applies (the direction key will then duplicate
the same kind of information from the relation).


On Jan 31 we had the number of highway=speed_camera +
direction=forward|backward|both as:

Global: 85
Brazil: 28 (32.94% of total)

On Mar 29 we had:

Global: 103
Brasil: 41 (39.8% of total)

And today (April 1):

Global:
highway=speed_camera + direction=forward|backward|both: 116
highway=speed_camera + other value for direction: 635
highway=speed_camera without direction: 31196

Brazil:
highway=speed_camera + direction=forward|backward|both: 55 (47.41% of total)
highway=speed_camera + other value for direction: 261 (41.10%)
highway=speed_camera without direction: 2998 (9.61%)


So it seems that this kind of "direction" usage is quickly growing here.


I have also included some common doubts at
https://wiki.openstreetmap.org/wiki/Talk:Tag:highway%3Dspeed_camera#Clarifications_about_common_doubts_and_how_people_view_speed_camera


Comments, please?