Extend ability to model shade at crags / sun angle

[killakalle]

Here are a few thoughts to think about and discuss:

Story: As a climber in hot and sunny Spain, I would like to know which crags have shade in the morning until roughly what time so that I can plan my climbing accordingly and not get grilled at the wall.

Variations of the story above are: morning <-> afternoon shade <-> sun (in winter)

This is a common problem, where I climb, and is as important as knowing the grade range and how to get to the crag. I am in a large local WhatsApp group of climbers. And every weekend there is somebody asking the question

"What sectors have shade in the morning?" or "Does anyone know when there is shade at X?"

In winter you get the same questions, replacing shade with sun.

I have started solving this myself with a Google Sheet. It's a good resource for myself. And I also point everyone to the sheet who is asking the question in the chat. However, I would like it even better if I could send everyone to theCrag for that type of information.

What I like about the sheet, is that you see all the climbing areas/sectors at once and can instantly see which sectors are sunny vs shady. In addition, you can tell at what time it changes from sunny to shady.

Link to the sheet: https://docs.google.com/spreadsheets/d/1RE-C6RH7BVahjQRYsL6s3iPxs7bM_P8QPa1zUyBcmDI/edit?usp=sharing

I am aware of the orientation tags. In my opinion, they cover part of the functionality, e.g. a northern sector will surely have shade around midday. But there are a couple of things that are not covered by orientation tags

• shade starts/ends at what time exactly
• what if shade is influenced by sth else than orientation, e.g. vegetation, mountain, cave

Also, the absence of the tag "Morning sun" does not mean that there is shade in the morning. It could mean:

• There is morning sun, but the tag is missing
• There is morning shade, but there is actually no tag for it.

What you expected:

• More details/possibility to model sun/shade for crags
• Overview of sun/shade times at different sectors (at different times of the year)

This ticket is related to https://github.com/theCrag/website/issues/2931

[Baschdl]

I like the user story by @killakalle and would add that the elevation of a crag also plays a big role in deciding whether a crag is "climbable" based on the sun (Countries like Switzerland can have crags which are close to each other but have an altitude difference of ~2000m).

I would propose a semi-automatic approach where a first step could be displaying the angle of the sun like over at mountainproject, e.g. https://www.mountainproject.com/area/118181654/drapel, which is way more helpful than "All day sun" on thecrag (https://www.thecrag.com/en/climbing/switzerland/yvorne-drappel). An extension of this could be displaying only the angles relevant for the crag based on the location polygon (one problem is that the polygons don't specify the orientation of the face but this could be deduced by the aspect tag or if that's not present by a digital elevation model (globally available ones have a resolution of 30m) as an initial guess (calculate the gradient around the location polygon) which can be corrected by a user). A second extension could be to factor in the surrounding topology by using a digital elevation model to deduce when the sun can touch the crag at all.

This approach would need far less user input than the suggested alternatives in #2931 by using only the location polygon and the aspect tag. It could answer @killakalle's "shade starts/ends at what time exactly" and it would be easy to factor in the different positions of the sun over a year (which wasn't discussed for a "user input" alternative in #2931). Lastly, it would be suitable for searching based on whether one wants sun or shade at different times of the day.

[Baschdl]

I did another quick experiment with the elevation model from #644 where the pink point is the crag:

Using https://github.com/zoran-cuckovic/QGIS-terrain-shading, we can easily calculate which parts are exposed to the sun and which are in the shade caused by the surrounding topography. This would be the sun at 110° (azimuthal angle) which resembles the sun in the morning and shows that the crag has shade:

and then in the afternoon with the sun at 225° (azimuthal angle) where the crag is sunny:

The altitude angle in both examples is 45° which is not correct. We would need to use the correct azimuthal and altitude angle for each crag depending on the date and time.

[rouletout]

@Baschdl könntest du mich bitte per email kontaktieren (ulf(at)thecrag.com)? danke!

[georg-d]

While the automated approach is a great help to instantly add an approximation of sun/shadow times for all cliffs, in the long run, we shall enable users to override it with more accurate data on any hierarchy level (crag/cliff/sector/route) - for example, because of insufficient resolution of elevation model & cliff geometry, vegetation (leaf cycle!), reflections by water or glass, and differences within one crag.

I really like the overview provided by @killakalle's sheet, much better than current textual descriptions. Due to the global scope of theCrag (the farer away from aequator the bigger differences between winter + summer), we'd need the overview to differenciate on time of year - a date slider above or besides the table would IMHO be clear to users, easy to implement, and helpful e.g. when planning vaccation.

As already discussed above and in https://github.com/theCrag/website/issues/2931 sun/shadow alone is IMHO not addressing the users need, but a more broad "when climbing is potentionally suitable/enjoyable" - think of snow, cold/hot wind, humidity,...