Proposed features/Local Hiking Scale
|Local Hiking Scale|
|Status:||Draft (under way)|
|Tagging:||[[Key:hiking_scale:<classification system>|hiking_scale:<classification system>]]=*|
|Definition:||System for tagging a local hiking scale|
|Rendered as:||According to value, could be color code, number or other symbol|
This Proposal describes a system for tagging the classification of a hiking trail according to a local scale. Such a scale is often indicated on guideposts.
In OSM, the tag sac_scale=* is traditionally used to describe the difficulty of a hiking trail. Even if this tag is used correctly, the value is subjective and often disputed between different mappers. Also, it is designed for demanding, high-altitude trails, and is unsuitable to describe nuances between easier trails.
Many regions use a local classification system for hiking trails, often devised by a climbing or hiking association. The number of distinct values in the scale varies, as do the used symbols; colour coding is quite common. A trail is usually rated by a group of local hikers/climbers who know the area, have seen it under different weather conditions, and use a consistent set of criteria to categorize it. The result is indicated on guideposts, e.g. as arrows or dots in different colours.
It makes sense to tag such a local classification in OSM because it is an objective and easily verifiable attribute of a trail, whereas the sac_scale value entered by a particular mapper always has a certain degree of subjectivity. Since this is a safety-relevant area, it is desirable to have as objective and reliable data as possible.
Structure and Values of the Tag
To describe a local hiking scale, as found on a guidepost, the following tag is used:
hiking_scale:<classification system> = <value>
where <classification system> is an abbreviation for the name of the system or the hiking/climbing organization that devises the scale, and <value> is the colour, number or other indicator used in this system.
For example, a trail categorised as difficult by the DAV (Deutscher Alpenverein, German climbing association), would be tagged hiking_scale:dav = black.
List of Classification Systems and Their Available Values
Many regions have their own classification system. Some use the same three colours, but the colour for "most difficult" in one system means "easiest" in the other. And sometimes two neighbouring systems use the same colour scheme but different criteria for classification.
In the Alps alone, a variety of systems is in use (). Even within the same country (as Austria or Germany) some regions use other systems than their neighbours.
Therefore it is necessary to describe for each classification system which values are available and what they mean. For each classification system the following information must be documented:
- Name of subkey (<classification system>)
- Names of available values
- Meaning of available values
If you add a new classification system please append an entry in the same style as the following examples. Sort the available values from easy to difficult.
Used in: German Alps
Example: hiking_scale:dav = black
Note: Some mappers have used the undocumented key dav_scale for this classification system.
Vorarlberg and Allgäu
Used in: Vorarlberg (Austrian Alps) and Allgäu (German Alps)
|yellow||Easy. Not particularly steep and no fall hazard.|
|red||Medium difficulty. Hiking boots recommended. Fall hazard possible.|
|blue||Difficult. Dangerous sections with fall hazards. Use of hands necessary for short climbing sections.|
|none||Not classified, i.e. no "official" guideposts. This information can be useful since such trails might fall into disrepair. Sometimes they are deemed dangerous, and guideposts are omitted deliberately to discourage hikers who have no alpine experience.|
Example: hiking_scale:valbg = red
Note: Some mappers have used the undocumented key vab_scale for this classification system.
How to Tag
While hiking, record the classification system and the value, as seen on guideposts or other sources (which are legal to use for OSM). If the classification system isn't documented on this page yet, add an entry in the section List of Classification Systems and Their Available Values above in which you define the subkey and describe the available values.
Add the appropriate hiking_scale:<classification system> tag to the way it describes, not to a guidepost.
You can add sac_scale=* additionally. The two complement each other very well when you use sac_scale=* to describe the actual difficulty of shorter sections within a trail, whereas the hiking_scale:<classification system> tag is usually given to a longer trail, even if only a few short sections within it have the indicated difficulty.
How Not to Tag
Do not use a conversion chart to translate the local classification system into other scales and add values for these other systems. Only add a tag for the classification system that is used locally and actually indicated on a guidepost or other source (which is legal to use for OSM).
Of course, if guideposts or other sources provide values for more than one scale, it is perfectly fine to add them all.
A local scale can be rendered by adding its symbol (colour) to a way or using different styles (width, dashed, dotted) for the line. Since the same colour can mean very different things in different classification systems, you should not show different classification systems on the same map. It is recommended to evaluate only one system for a local map.
A conversion table could be used to translate local classification systems into a common scale, e.g. for use in Garmin maps. It is probably better to use sac_scale for this purpose, however. Where sac_scale is missing, a local classification system could be used to evaluate the difficulty of a trail.