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Most useful webapp, ever!

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Joined: Fri Dec 14, 2012 10:45 am

Re: Most useful webapp, ever!

Postby mattyj » Fri Dec 14, 2012 2:06 pm

This thread caught my attention, and I hope I can chime in without violating the no self promotion rule.

I'm the developer behind caltopo, and as luck would have it I'm actually in the process of redoing the slope shading layer. The existing layer was an experiment in mapping avalanche forecasts to real world terrain, and as a result there's a heavy emphasis on aspect as well as slope. The underlying data is stored as slope-aspect polygons, and performance considerations led me to limit the number of slope colors in order to limit the number of polygons. There is indeed a huge difference between 28 and 35, but I was trying to highlight the angles where most slides occur (35-45) and extend the yellow color down to the point where there's little risk of a slide. It's also gotten a lot of use for generic routeplanning outside of an avalanche context, and the slope ranges I picked don't make sense for those users.

I don't know if user customization is going to be possible with the new layer, but assuming not - I'm still not sure what it should look like. What colors to use for what angles, whether to do a gradual blend between colors or have discrete steps, how to make something that appeals to both scramblers and skiers, and so on.

Thoughts?

NB: To tie this back to the original post, Ryan from hillmap is pulling in my slope shading layers, if you happen to prefer his split-screen approach. It's on the right under the "data and analysis" tab.

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Re: Most useful webapp, ever!

Postby Dave B » Fri Dec 14, 2012 5:49 pm

Thanks for the input, Matt!

Before I found CalTopo and HillMap, I'd spent quite a bit of time trying to make some .kml files with slope shading in ArcGis from 10 m resolution DEMs. I played around with the color range quite a bit and found that I, personally, throught red for 35-45, Orange for 32.5-35 and deep orange for 45-47.5. Yellow for 30-32.5 and deep yellow for 47.5-50 and green for 20-30 and deep green for 50-60.

As you mentioned, I would imagine the green->red color scheme wouldn't be useful to scramblers so I also wonder if a specific layer for slope angle as it relates to avalanche forecasting and then another layer for slopes 0-90 degrees for those interested in slope angle across the entire gamut.

What I'd really love to see is the ability to export the slope angle overlay, only, as a kml file. I've tried to do this in CalTopo and it seems that a basemap has to be included in the export instead of the polygons used for slope shading.

You've made a great product though!
"There is no cheating in climbing, only lying." - Semi-Rad

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Re: Most useful webapp, ever!

Postby mattyj » Fri Dec 14, 2012 6:04 pm

Dave B wrote:What I'd really love to see is the ability to export the slope angle overlay, only, as a kml file. I've tried to do this in CalTopo and it seems that a basemap has to be included in the export instead of the polygons used for slope shading.


That's because Google Earth doesn't properly handle transparent images. I tried doing this with both slope shading and contour lines, and some percentage of them showed up with black backgrounds. There was no consistency as to which tiles worked and which didn't - if I restarted GE, a different set would show up broken. Posted on Google's help forums and they never replied.

If you want a KML file for something other than GE, you can fake it by looking at the GET request for the KML file and eliminating the basemap layer (so layer=slp) from the request.

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Re: Most useful webapp, ever!

Postby dpbasing » Sat Dec 15, 2012 7:51 am

cool TY for sharing.

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