Thread: online slope mapping tool

I've been working on a map overlay that allows you to shade slopes by angle and/or aspect. I think it's a good high-level visualization of potential avalanche starting zones that can assist with safe route planning in unfamiliar terrain. I've listed some known limitations at http://caltopo.blogspot.com/2012/02/...-analysis.html, and it's important to note that while you can do danger-rose-style shading of slopes, avy forecasts are regional and not produced with slope-level accuracy.

This is experimental and I'm looking for feedback on it. click here, then hit the binoculars in the top right to enter a location and the +2 to adjust the slope shading. Here's an example of Shasta, out in my neck of the woods: By Angle By Aspect





Notes: The WY base maps are low-res but will be fixed this spring when the USGS finishes scanning new ones. You can also log in and create maps like this, but that's neither here nor there with slope shading. If you're familiar with hillmap.com and like that better, I've been talking with the guy who created it and he's going to pull in the slope shading as well. Shading may be a little slow to load but I'm working on the performance issues.

Interesting idea. Used the search function to look up the presidential range in NH and a few other interesting spots around these parts and everything looked pretty good through the Dolphin browser on an ipad2.

Would be cool if rotation was available in a similar way to google earth, with their 3D topo rotation and your coloring scheme being pretty much the ideal. Hell, I might even pay for that!

**Edit to say this is useful for trip planning in general not just avy awareness, and therefore should be in ski/snowboard where it will see more traffic....

There is quite a bit of this going on in professional circles... in BC terrain mapping from an avi prediction perspective is getting bigger and is (becoming) a necessity in high elevation/deep snow logging, high elevation mining and in planning for rec tenures. As for an online tool I'm no help... all the stuff I have seen or dealt with is in the Arc GIS realm.

I've been playing with arc lately and was thinking about how useful it could be in variety of ways when it comes to avalanches.

These overlays seem like a good idea, and I think could be incorporated with google earth pretty easily. I have an earth overlay with topos, the ability to tilt and pan topo maps is great, so I imagine this too would be doable.

3D rotation (much less tilt) isn't going to happen through the web map interface, unfortunately. Closest I could come would be orienting N on one of the 4 cardinal directions, and even that would take some serious work.

If there's enough interest I could make some variation of this available for Google Earth, but it's not as simple as snapping my fingers. The shapefiles are around 500MB per 1 degree block; Google Earth can't import the whole thing, so I'd need to chunk it up at a minimum, and possibly combine polygons with different aspects but same slope. I'd definitely want to make sure that my slope coloring choices make sense to people first, since it's not the sort of thing I'd want to have to redo.

I'm always a little hesitant to come on to a new forum and start pimping my own stuff, which is partly why I posted here about the avy shading specifically rather than ski/snowboard . . .

I see, i was hoping it was a simple to make .kmz files for google earth from your data layers. But i dont have any idea how thats done, or how you're doing things.

You should consider it for the the future though, it adds some great capability for route finding.

Really cool - spreading the word. It didn't seem to be working last night but it's working great now.

Thanks. The server has been having some problems as the shapefiles I'm using are just too damn big; I've had to restart it twice when I noticed it was down.

Should be fixed sometime early next week as I'm creating a new, smaller shapefile set.

Two comments:
I'd make the key a bit more readable. It's sort of tucked away down in the corner and it took me a while to figure out what the colors meant. Maybe move it up to the main toolbar in the upper right and instead of making the font of the numbers the color, can you have a solid block next to the numbers?

Second: You say that you are using shapefiles, but it looks like a grid based display. If you could convert things to a vector based format, it would make it easier to convert to a .kmz and also make display quicker.

All in all very cool. Is this just a side project or something connected to other work?

They're shapefiles derived from raster elevation data, which is why they look blocky. The problem is just the number of polygons, in part because I'm breaking the data up by both aspect and slope. Google Earth just can't handle KML files that large. I'm going to look into generating a custom KML file for small coverage areas that points to my map tiles (topo as well as slope shading), but I don't know how well that will work out.

This started as a way to get better maps for SAR - we were working with a topo program, a park trails map, maybe google maps satellite, with no way of lining them up. End result is a total cluster and people never had a good visualization of the search terrain. We can take the site plus a bunch of sar-specific features, box it up with map data and run it in the field miles from the nearest internet connection. I'd like to find a way to turn the site into an alternative to boxed topo software that can actually pay some bills, but I'm not sure how to do that yet. It might require a split from the SAR codebase, since supporting both is starting to make some UI changes a little cumbersome.

I should add: for any interested sar volunteers, I can get you a copy of the codebase and all the map layers from caltopo.com for your state. PM me.

Everyone I've emailed this out to thinks this is a really neat tool. I would bet you could get people to pay a one time $10 fee to use the site, or maybe give them access to certain tools. I'm not sure it's something that many people would pay a subscription for, but for route planning it seems really useful.

Thanks - it's good to hear that people like it.

In case my last post was confusing: I have no plans to ever charge people for the basic map viewing/editing features currently available, and I'd feel very bait-and-switchy if I did at this point.

You should consider doing what lots of podcasts are doing these days - set up an affiliate link to amazon and tell people to click through next time they shop. You might be surprised at the amount of income that would generate.

Thread revival . . . I've added a KML export feature that lets you load the slope shading into Google Earth. Go to http://caltopo.com/map.html, center/zoom so that what you see on screen is the area you'd like to export, and click "Export to Google Earth" on the new left bar. Dialog appears at the bottom of the page; select the layer you'd like and hit Export. I try to export a 16x16 grid of tiles, so zooming in will give you a higher resolution overlay in Google Earth.

Unfortunately it seems like Google randomly decides to honor or ignore the tiles' alpha layer, so the slope shading is a mix of semitransparent and fully opaque. If anyone has any insight into this I'd love to hear it.

Anyway, give it a try and I'm open to suggestions about how to change/improve it.

This is very cool. Very useful tool.

Please keep working on the Google Earth export feature. Integrating layers into Google Earth makes it much more user friendly for planning your route. If you can solve the problem of opaque/transparent so that you can overlay the slope angles over Google Earth without obscuring everything else, this will be a truly awesome app.

Thanks for your work on this.


What exactly are the slope angle parameters that the various colors represent? I understand that white is flat, green is gentle, yellow is steep, red is steeper yet, and purple is very steep, but what angles are associated with those descriptors?

It's on the bottom right of the screen; it's a to-do item to make it less subtle but I've been distracted by other things like the KML export.

G: 20-27
Y: 28-34
R: 35-45
B: 46+

Basic idea being to highlight a few general ranges - the critical 35-45 slope where most slides happen, slopes down to ~30 where slides typically "can happen" out by the coast, and going lower as I've read about numbers down to 20 in the right conditions in a continental climate.

Probably better to bump this thread than start a new one . . .

I need to upgrade the slope shading for technical reasons, and I want to take the opportunity to improve it as well. Right now I'm looking at making 2 versions, one with continuous gradients and the other with fixed colors/levels like the current setup. IMO fixed levels are more useful for avy terrain as it's easier to tell the exact slope angle, but the continuous gradient is nicer for generic trip planning and other activities. Here are some mockups:

Gradient:


Fixed:


Fixed version is 20-26 = green, 27-29 = yellow, 30-31 = light orange, 32-34 = dark orange (hard to tell light v. dark without zooming in), 35-45 = red, 46-50 = purple, 50+ = blue. Gradient version roughly matches.

Some more information and another set of example images at http://caltopo.blogspot.com/2013/01/...revisited.html. Looking for input on what the colors and ranges should be, or any other changes, before rendering the layer out. What would you like to see to help with route planning?

In Google Earth:

I think fixed level works better for this type of application so you know for sure which slope class you're looking at.

Looks great!