App for determining sun/shade at a specified location&time

Sport Climbing seems like the right place to post this....

Asking climbing software developers in particular:

How hard would it be to take GIS data for some area of high topological relief, combine it with astronomical data, and develop a sun/shade model that could give fairly accurate estimates of when a crag goes in/out of the shade.

Not talking about a route line specifically, or a cragwall. Those seem like they could easily be determined secondarily once determining the whole sun-horizon-crag interplay.

Canyons and valleys are the main landscapes for intended use.

Seems like the kind of thing that could easily exist with high enough resolution gps/elevation data, but maybe not super high demand for an easy to use publicly accessible tool?

So, dear nerds, what would it require to build something like this? Or does it already exist and my web search skills are lacking?

(Yes, this is not in the spirit of adventurousness. Convenience, rather. Yes it would be great to just go “learn the conditions the old fashioned way”, but that’s not always as fun as it sounds.)

p.s. 

Band name: Algo and the Rhythmics.
Dibs, called it.
First album title: The General Solution.
First track title: Initial Conditions
Last track title: Mutiny on the Boundary

MP does this. Go to the map of a crag and click the sun angle box.

MP shows the general sun angles for a given day, which generally indicates sunrise and sunset...

... but I believe that feature does *not* factor in local topology or specific gps coordinates.

Eager to be proven wrong, but I just pulled up the sun angles and moved the focal point all around boulder canyon - got no visible indication they were dynamically adjusting. Definitely not able to determine if its looking like at 415 or 445 sunset at a specific location.

edit: looks like it does factor in latitude, but not topo relief. Thats the part I’m curious about. Would obviously be dependent on high resolution topo data to be any more useful than the “sun angles” tool.

(Obligatory “Do not cite the deep magic to me, witch. I was there when it was written.”)

Caltopo.com does this well.

Woah, Caltopo is pretty neat. Has a lot of Flatirons and BoCan crags already labelled. Here's Animal World projected at 9:30AM, crude but helpful. No longer need a masters degree in celestial mechanics to stay warm.

Adam bloc wrote:

Woah, Caltopo is pretty neat. Has a lot of Flatirons and BoCan crags already labelled. Here's Animal World projected at 9:30AM, crude but helpful. No longer need a masters degree in celestial mechanics to stay warm.

Brilliant! Thanks y’all!

Photographers Ephemeris works quite well.