[Tagging] The direction=* tag

Tod Fitch tod at fitchdesign.com
Thu Mar 16 04:13:42 UTC 2017


The “direction” tag [1] has different uses that seem disjoint to me.
To specify the orientation (compass point or degrees from north) of an object (adit or cave entrance, etc.). 
To specify direction (clockwise/counterclockwise) around a roundabout (not sure why this is needed as it should be apparent from local laws or specified with a “oneway=yes”).
To indicate the direction (forward/backward) a stop or yield (give way) sign has effect along a way.
Oddly, that third use seems only for stop and yield signs but not for traffic signals where a “traffic_signals:direction=forward | backward” tag is to be used. However that seems to be the most used form [2]. Apparently some have figured that if we have “traffic_signals:direction” there should be “stop:direction” [3] and “give_way:direction” [4] tags.

And other things where a direction like tag might be used, like roof aspect have their own tags (“roof:direction=*”) [5] which follow the syntax and semantics of the first definition of the “direction=*” tag.

It seems to me that the first and the third definitions should be split into separate tags with the second definition deprecated.

From a data consumer point of view, there may not be a conflict as map rendering is likely to only use the bearing definition while routing would use the forward/backward definition. Though I suppose that a really detailed map may wish to show the actual angle of a stop or yield sign as they are not necessarily exactly aligned with the traveled way. From a mapper’s point of view having totally different  meanings for a tag based on context seems confusing.

Since the “forward” and “backward” values are most used, it may be reasonable to keep the third definition of that tag even though it is inconsistent with “traffic_signals:direction”.

Should we come up with a new tag to replace the angle/aspect meaning of the “direction=*” tag? If so, what tag name would make sense.
“Bearing” (some uses which seem to follow the first definition of “direction”) [6]
“Aspect” a couple of instances in use but not clear to me what was intended. [7][8]
Thoughts?

[1] https://wiki.openstreetmap.org/wiki/Key:direction
[2] https://taginfo.openstreetmap.org/keys/direction#values
[3] https://taginfo.openstreetmap.org/keys/stop%3Adirection
[4] https://taginfo.openstreetmap.org/keys/give_way%3Adirection
[5] https://wiki.openstreetmap.org/wiki/Key:roof:direction
[6] https://taginfo.openstreetmap.org/keys/bearing#values
[7] https://taginfo.openstreetmap.org/keys/Aspect#values
[8] https://taginfo.openstreetmap.org/keys/aspect#values



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