Shifting in Satellite Imagery

Richard Marquis's Avatar

Richard Marquis

20 Apr, 2021 04:07 PM

Hello. In preparation for backpacking trips, I usually generate my base map by snapping my line to either OSM of NFS trails. Then I use the google satellite imagery to modify the line to match what the trail actually does (Assuming it's visible). I'm mapping a route in the Bob Marshall Wilderness, and there seems to be some shifting between the google satellite, the NAIP layer, and the Global Imagery Layer. The coordinates for the area where I'm looking are 47.7895, -112.9402. In hat area, the NAIP and Global Imagery layers appear to match up. I'm sure you're aware of discrepancies with respect to the satellite layers, but I'm wondering if there is a way to know which layer is accurate. Thanks so much.

  1. Support Staff 1 Posted by akaufmann on 20 Apr, 2021 05:46 PM

    akaufmann's Avatar

    Huh, this is very interesting... it appears to be an error in the google satellite image.

    I say this because:
    1. NAIP and GlobalImagery layers agree with each other.
    2. NAIP and GlobalImagery seem to correlate with other layers (MapbuilderTopo, Sentinel, etc).
    3. Google Satellite seems to have lost Gates Lake at 47.7813, -112.9412.
    4. There appears to be duplicate data in a vertical path near the longitude -113.0077.
    5. If you toggle between Google Satellite and one of the other Imagery layers, you can see there seems to be some data which has been shifted to the right.

    Of course the best way to figure it out would be to go in person and see for yourself :)

    Unfortunately this isn't our layer, so there's nothing we can do about it (thank goodness -- I don't think this would be an easy error to fix!).

    Cheers,
    AJ

  2. akaufmann closed this discussion on 20 Apr, 2021 05:46 PM.

  3. Richard Marquis re-opened this discussion on 20 Apr, 2021 05:48 PM

  4. 2 Posted by Richard Marquis on 20 Apr, 2021 05:48 PM

    Richard Marquis's Avatar

    Thanks so much AJ. That was what I suspected. I was wondering what happened
    to Gates Lake as well. I appreciate you looking into it.

    Rich

  5. Ben Lantow closed this discussion on 20 Apr, 2021 11:37 PM.

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