Spike at 34.34086, -118.55631

Jordan Brown's Avatar

Jordan Brown

07 Nov, 2021 08:05 PM

I know that Caltopo gets its data from elsewhere, but this still seemed interesting.

In the MapBuilder Topo layer at 34.34086, -118.55631 there is a feature that I can only describe as a spike. It's in a mountainous area, yes, but the contours say on one of the ridgelines there's a feature maybe 250' x 120', that's 500' tall. I haven't been super-close to that particular piece of mountain, but I think I would have noticed such a distinctive object.

I'd say that it's just an error in the elevation data that the contours are built from, but interestingly it does not appear in any of the other data - and notably not in the elevation that you get by hovering, or in the outlines from "view from here".

Maybe there are multiple sources of elevation data and the error is only in one of them.

  1. Support Staff 1 Posted by akaufmann on 08 Nov, 2021 07:04 PM

    akaufmann's Avatar

    Jordan,

    Unfortunately elevation data is prone to various errors that can cause artifacts like the one you've identified here (in some cases they may appear as holes). Our contour lines were generated a couple years ago using the national 1/3rd arcsecond dataset but we're always updating the elevation data as higher resolution datasets become available. When we do so, we do not normally update the contours because we haven't seen a meaningful enough difference to merit.

    As you can see on our coverage map (https://caltopo.com/l/CM87), this particular area has been updated with newer lidar data, so that would explain why the error only appears in the contour lines. We may consider regenerating the contours using the new data once we have more complete coverage but for now, these sort of artifacts (while annoying) are generally easy to identify and ignore so this is not a high priority at the moment.

    Sorry for the inconvenience!
    AJ

  2. akaufmann closed this discussion on 08 Nov, 2021 07:04 PM.

  3. Jordan Brown re-opened this discussion on 08 Nov, 2021 09:57 PM

  4. 2 Posted by Jordan Brown on 08 Nov, 2021 09:57 PM

    Jordan Brown's Avatar

    No worries, not an inconvenience, just... interesting.

  5. akaufmann closed this discussion on 08 Nov, 2021 09:59 PM.

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