what slope angle numerical range does the ~blueish color represent?

 Moses's Avatar

Moses

03 Jan, 2021 07:05 AM

At the center of this map https://caltopo.com/map.html#ll=39.33245,-120.1507&z=21&b=f16&a=sf%2Csntl%2Cwx , what numerical slope angle range does the ~blueish color represent?

(I do not see ~blue in the slope angle shading key that shows yellow 27-29, light orange 30-31, orange 32-34, red 35-45, purple 46-50.)

THANKS FOR YOUR GREAT PRODUCTS AND FEATURES!

  1. Support Staff 1 Posted by Ben Lantow on 04 Jan, 2021 02:11 AM

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    That is a shade of purple. This is far too granular a use of this layer, it is not representative of conditions to that level of interpretation. When you zoom back out you'll see that is a purple hue when combined and visible with the pixels around it. The slope angle shading is designed and intended to be interpreted in aggrate.
    Best,
    Ben

  2. Ben Lantow closed this discussion on 04 Jan, 2021 02:11 AM.

  3. Tom Cal re-opened this discussion on 04 Jan, 2021 03:54 AM

  4. 2 Posted by Tom Cal on 04 Jan, 2021 03:54 AM

    Tom Cal's Avatar

    Thanks!

    Do the different shades of purple mean anything?

  5. Support Staff 3 Posted by Meghan on 07 Jan, 2021 11:02 PM

    Meghan's Avatar

    Tom,

    As Ben said above, the slope angle shading is designed and intended to be interpreted in aggregate. If you use the key provided, the color purple is used for slopes between 46-50 degrees.

    Best,
    Meghan

  6. Meghan closed this discussion on 07 Jan, 2021 11:02 PM.

  7. Tom Cal re-opened this discussion on 08 Jan, 2021 01:24 AM

  8. 4 Posted by Tom Cal on 08 Jan, 2021 01:24 AM

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    Is there a slope angle shading color for slopes greater than 50 degrees
    steep?

    What do you mean when you say "interpreted in aggregate "?

    Is there a specfic zoom level above which you feel people should not use
    CalTopo slope angle shading?

  9. Support Staff 5 Posted by Ben Lantow on 08 Jan, 2021 11:25 PM

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    Hey I'm so sorry I looked closer at this color and it is actually distinct blue. The full key is in the top right corner of the map (see screenshot), just kinda looked more purple to me until Matt also looked at it and pointed out it's blue.

    Slope Angle Shading can provide insights in a variety of ways but typically that would be use case specific, we're trying to impart that on a pixel by pixel basis you shouldn't be trying to use this to plan or understand terrain. Turning on satellite in this case we're looking at what appears to be an embankment. Instead look at the information provided in a larger picture way given the context and surroundings.

    Best,
    Ben

  10. Ben Lantow closed this discussion on 08 Jan, 2021 11:25 PM.

  11. Tom Cal re-opened this discussion on 09 Jan, 2021 06:49 PM

  12. 6 Posted by Tom Cal on 09 Jan, 2021 06:49 PM

    Tom Cal's Avatar

    Thanks!
    Re " Slope Angle Shading can provide insights in a variety of ways but
    typically that would be use case-specific, we're trying to impart that on a
    pixel by pixel basis you shouldn't be trying to use this to plan or
    understand terrain."

    Thanks for your viewpoints!

    I integrate information from maps into my trip planning, and into my boots
    on the dirt and boot son the ground scouting, that I condiuct on days when
    there is no snow on the ground and days when the avy danger rating is low.

    In this case, I used mas as 1 tool to help plan a hiking route on dirt that
    would get me down to the river to watch for birds and hawks and stuff. I
    found that the CalTopo map, from the comfort of my couch, helped
    me identify what might be a steep embankment that I might want to avoid. I
    did not trust the map about this, but did use this "clue" to form a
    "guess/hypothesis": about what I might see when I visited this terrain with
    boots on the ground. (It turned out, I saw a steep embankment that I
    avoiuded.)

    Thanks again for your insights and viewpoints! Great products!

  13. 7 Posted by Moses on 09 Jan, 2021 09:02 PM

    Moses's Avatar

    BTW, here's a feature request related to these topics:

    https://help.caltopo.com/discussions/features/4282-include-all-slope-angle-shading-colors-in-the-key-below-the-map-overlays-slope-angle-shading-checkbox

    "Include all slope angle shading colors in the key below the Map Overlays slope angle shading checkbox

    Currently, on CalTopo "desktop" web-browser maps, the key below the Map Overlays slope angle shading checkbox only goes up to 50 degrees.

    Suggestion: Include all slope angle shading colors and angles in the key below the Map Overlays slope angle shading checkbox, perhaps by having the key wrap to a 2nd line. Just an idea, not a big deal.

    Thanks, great products!

  14. Julie closed this discussion on 12 Jan, 2021 09:34 PM.

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