[Tagging] layer=-1, rivers, bridges and tunnels

Fernando Trebien fernando.trebien at gmail.com
Fri Mar 14 14:51:47 UTC 2014

Hello everyone,

This is a small issue that came up recently in Brazil. In my
understanding, the layer tag has no specific meaning other than to
specify a rendering order. The wiki, however, states that it is wrong
to tag a whole river with layer=-1. The reason for that, as far as I
could figure, is because current validators (such as JOSM's or
KeepRight's) will not issue a warning on a waterway x highway crossing
when their layers are different, leading some users into tagging the
river with layer=-1 in order to get rid of warnings about missing
bridges and tunnels. So, I think that the validation rule is
inadequate: it should warn when a waterway crosses a highway that has
no bridge or tunnel tag, regardless of the value in the layer tag.
(Fords are the only exception, AFAIK.)

Do you agree that the river can be tagged with layer=-1 as long as
this value is correct in relation to the layer of other
nearby/crossing ways?

Fernando Trebien
+55 (51) 9962-5409

"The speed of computer chips doubles every 18 months." (Moore's law)
"The speed of software halves every 18 months." (Gates' law)

More information about the Tagging mailing list