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OpenDroneMap / OpenSfM

Open source Structure from Motion pipeline
GNU Affero General Public License v3.0
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Altitude is negative #30

Open sbonaime opened 2 months ago

sbonaime commented 2 months ago

Hi, I found this in log for a specific set. Altitude is negative (-X.XXX) : viewing directions are probably divergent. Using default altitude of 1.0

As Altitude is get from GPS data it maybe it is not a good idea to set it arbitrary to 1.0 Sometimes we can have images taken below GPS Sea level value (https://en.wikipedia.org/wiki/List_of_places_on_land_with_elevations_below_sea_level)

Could it be possible to force (with an option) the found negative altitude ? Thanks

smathermather commented 2 months ago

Proposed pull request to address, keeping it simple: if Z is below Lake Assal, it's probably invalid, but treat as valid otherwise: https://github.com/OpenDroneMap/OpenSfM/pull/32

sbonaime commented 2 months ago

@smathermather I am now using ODM for underwater data ... so maybe we can have an option for real underwater images ?

smathermather commented 2 months ago

This would work for any underwater images above the Afar Depression, but I just realized the Dead Sea is lower. I've changed the proposed value. So, anyone doing underwater images on the Dead Sea will be out of luck, or need to change their version.

This also applies to areas where the geoid is well below the ellipsoid, which is an even longer list than the above. Much of the coast of Tanzania is below sea level on the elipsoid, but the India Ocean hasn't read the map, so folks stay dry enough.

smathermather commented 2 months ago

@sbonaime -- do you have an example dataset you can share for testing?