Proposal:Incline:across
| Tag for lateral inclination | |
|---|---|
| Proposal status: | Draft (under way) |
| Proposed by: |  Wielandb (on osm, edits, contrib, heatmap, chngset com.) on behalf of  OPENER (on osm, edits, contrib, heatmap, chngset com.)
|
| Tagging: | incline:across=* |
| Applies to: | 
|
| Definition: | specifies lateral inclination of a way |
| Statistics: |
|
| Rendered as: | hidden |
| Draft started: | 2014-06-08 |
Proposal
This proposal wants to establish the key incline:across=* as a way to record the incline of a way in the direction perpendicular to the movement direction, in other words how much the way is tilted to the left or the right.
Rationale
This information is valueable to be recorded because at a steepness of 2.5% across a way, it becomes no longer usable for (especially electrical) wheelchair users. Also, a sloped way with a surface of dirt may become inaccessible after rain because one would slip away. Similar to incline=*, the proposed key incline:across=* describes lateral inclination, see Cross Slope on Wikipedia. The key incline:across=* was chosen to be in line with the already established incline=* tag. It is already in use by some wheelchair-routing projects, like Namo in Germany and Access2Life in Austria.
Tagging
The tag should only be used on ways . The lateral inclined section should get the tag incline:across=value% on the way. The incline is most commonly given as percentage values (postfixed with a percent sign, %), e.g. incline:across=7%. Degree-values should only be used in places where giving an incline in degrees is more widespread than giving it in percent (postfixed with a degree sign, °), e.g. incline:across=10°. The value should be given for the practical maximum lateral incline on the steep section (i.e., the maximum lateral incline that a vehicle/primary user could achieve), and not for the average incline between the nodes. Positive values indicate movement downwards to the right side, looking in the direction of the way and negative values indicate movement downwards to the left side, looking in the direction of the way (similar to natural=cliff). The tag has no practical use on closed ways 
, nodes 
and relations 
, as those have no clear direction in which a lateral slope would go.
Examples
Tip: Relationship between percent and degree values
A percentage value gives the corresponding vertical distance when multiplied by the horizontal distance travelled. A value of 2% (the compulsory lateral inclination for a sidewalk to allow the water to drain) would indicate a 2 cm vertical gain on the width of 1 m.
Note that a 10° incline is not the same as a 10% incline. A 10° incline is actually a 17.63% incline, and a 10% incline is actually a 5.71° incline. Values can be converted as follows:
<incline in %> = tan(<incline in °>) * 100
<incline in °> = arctan(<incline in %> / 100)
Rendering
No special rendering is suggested for general-purpose map styles such as carto. However, special-interest map styles may adopt a special rendering to show the incline. JOSM already renders incline:across=* in the style “Wheelchair Routing Attributes” as a colored slope symbol across a way like this: 
Features/Pages affected
External discussions
Comments
Please comment on the discussion page.
Special Thanks
Special thanks to Species (on osm, edits, contrib, heatmap, chngset com.) for doing the initial work on this proposal!