Contents: Paths and the SAC hiking scale

OpenStreetMap grades paths
The SAC Mountain and Alpine hiking scale
Path visibility

OpenStreetMap grades paths

There are several things it would be useful to know about a path. Is it well waymarked, how hard or dangerous is it, are there sections which are hard to see on the ground, how big is it, etc.

OpenStreetMap allows the person adding a path to the world map to include a lot of useful extra information about that path. That in turn may become an integral part of the electronic maps based on the OpenStreetMap data. At least some of this information may be ‘read’ by a navigation app and presented on the map by making the paths colour and pattern match the information recorded by the path’s uploader.

In good conditions the Pyg Track on Snowdon is a straightforward mountain path. The Crib Goch ridge just above is a famously rocky knife edge with significant drops and requires hands on rock to stay secure. That is reflected in the blue and black path colours on the OpenAndroMap below. Those paths are both marked on the OS mapping but using identical path markings.

The SAC Mountain and Alpine hiking scale

Perhaps a couple of things that we most want to know about a path is “how hard and dangerous is it”? OpenStreetMap uses the Swiss Alpine Club (SAC) Mountain and Alpine Hiking scale to grade hiking paths. This is used wherever the path is in the world.

SAC scale	Swiss Alpine Club trail description
T1	Well-constructed footpath. Where possible, all exposed areas are made secure with fixed cables, railings, etc. The risk of falling can largely be ruled out with normal behaviour.
T2	Continuous established footpath. Exposed areas made more secure. Partially steep terrain. Risk of falling not ruled out.
T3	Path not always obvious / visible. The more exposed areas can be secured. You may need your hands for balance. Some exposed areas remain, where there is a risk of falling. Pathless sections over scree or talus.
T4	Occasionally pathless. In certain places you’ll need to use your hands. Some quite exposed terrain, e.g. steep grass slopes, rock ledges, simple firn fields and minor glacier passages (with little crevasse risk).
T5	Often pathless. Individual easy climbing secions. Exposed, challenging terrain, steep cliffs. Bare glaciers and firn slopes which posed some risk of falling.
T6	Mostly pathless. Grade II scrambling. Often very exposed. Terrain examples: Dangerous talus slopes, rock gullies, steeper sections of snow-free glaciers = increased risk of falling.

Below is a screenshot of OpenStreetMap’s web-editing interface. You can see some information that may accompany a ‘path’.

OpenAndroMaps and OsmAnd maps contain this SAC scale information. If you choose the hiking style/theme for an OpenAndroMap or switch on the ‘Alpine hiking scale (SAC)’ switch in OsmAnd then the path markings on those maps will change to reflect those SAC path grades.

The actual colours and patterns used in OsmAnd mapping are different to those used in OpenAndroMaps. Check the map key/legend for the map you’re using.

Note: There’s no guarantee that a difficult path will be marked as tricky. A nav app can only accurately show the path’s difficulty if the path uploader bothered to include the SAC scale rating. However, if you do see a black path on an OpenAndroMap (for example) you’re unlikely to be able to stroll along it with your hands in your pockets. If drop-offs and easy scrambling are not your thing then avoid these.

Here’s the Swiss Alpine Club’s official guide to the scale.
How the scale is implemented within OpenStreetMap is explained in this OpenStreetMap wiki.

Path visibility

Path visibility is another thing that might be shown on OpenStreetMap-based maps. eg OpenAndroMaps change the path pattern and dash frequency to show sections where the path might be hard to spot. ‘Trail-visibility’ is explained in this OpenStreetMap wiki.

These extracts from the OpenAndroMap key for the ‘Elevate’ hiking theme explain how OpenAndroMaps mark hiking paths.