Negative altitude inconsistency

[Gordon]

Running the same set of 68 images full size (M2P 5472pixels wide) vs resized to 3644 to allow GPU feature extraction brings up this oddity.

Full sized I see this message re altitude/altiude/altide (I assume they are all meant to be altitude!)

[INFO] running “E:\WebODM51\resources\app\apps\ODM\SuperBuild\install\bin\opensfm\bin\opensfm” match_features “E:\WebODM51\resources\app\apps\NodeODM\data\dd0f4f37-d16d-42bf-b503-43db3d4274f0\opensfm”
2022-02-25 12:46:29,949 INFO: Altiude is negative (-0.4408570216158178) : viewing directions are probably divergent. Using default altide of 1.0
2022-02-25 12:46:29,949 INFO: Altitude for orientation based matching 1.0
2022-02-25 12:46:29,963 INFO: Altiude is negative (-0.4408570216158178) : viewing directions are probably divergent. Using default altide of 1.0
2022-02-25 12:46:29,963 INFO: Altitude for orientation based matching 1.0
2022-02-25 12:46:30,015 INFO: Matching 760 image pairs

resized gives no weird altitude message

[INFO] running “E:\WebODM51\resources\app\apps\ODM\SuperBuild\install\bin\opensfm\bin\opensfm” match_features “E:\WebODM51\resources\app\apps\NodeODM\data\447f4c08-9d52-4322-9e5f-c7d90340b4c2\opensfm”
2022-02-25 08:46:31,801 INFO: Matching 732 image pairs

The images are all taken from around 700-800m ASL.

[pierotofy]

Mm, strange! How did you resize your images?

[Gordon]

Just used “resize images” at the start.
However, it’s the unresized images giving that message.

Either way, the process finishes with a decent 3D model.

[Gordon]

And despite that message, this -

M2P manually flown, stopped for images from various heights, mostly non-nadir.

[Gordon]

Any idea on what the issue might be with full size images giving this error?

I’ve just been down the road collecting over 800 images of a few sections of our road, which is in terrible condition, full of potholes, and I’m seeing this error again.
Processing continues past this error, but it would be nice to know why I’m seeing it.

[INFO] running “E:\WebODM\resources\app\apps\ODM\SuperBuild\install\bin\opensfm\bin\opensfm” match_features “E:\WebODM\resources\app\apps\NodeODM\data\aa3fad0a-98c6-485a-bab4-ce83d9451907\opensfm”
2022-03-13 14:30:17,244 INFO: Altiude is negative (-77.26879427249487) : viewing directions are probably divergent. Using default altide of 1.0
2022-03-13 14:30:17,244 INFO: Altitude for orientation based matching 1.0
2022-03-13 14:30:17,266 INFO: Altiude is negative (-77.26879427249487) : viewing directions are probably divergent. Using default altide of 1.0
2022-03-13 14:30:17,266 INFO: Altitude for orientation based matching 1.0
2022-03-13 14:30:17,335 INFO: Matching 1309 image pairs

The few images I’ve checked have altitudes in the 550-575m ASL range listed in EXIF.

[Gordon]

It isn’t just my images, I’m seeing it with these M2P images (from Challenges with edge of rooflines thread) too, with altitude 73km below ground!

[INFO] running “E:\WebODM\resources\app\apps\ODM\SuperBuild\install\bin\opensfm\bin\opensfm” match_features “E:\WebODM\resources\app\apps\NodeODM\data\fb777e29-8f26-4359-bcd5-83a3a9e408f8\opensfm”
2022-03-16 12:07:49,153 INFO: Altiude is negative (-73335.1684565068) : viewing directions are probably divergent. Using default altide of 1.0
2022-03-16 12:07:49,153 INFO: Altitude for orientation based matching 1.0
2022-03-16 12:07:49,184 INFO: Altiude is negative (-73335.1684565068) : viewing directions are probably divergent. Using default altide of 1.0
2022-03-16 12:07:49,184 INFO: Altitude for orientation based matching 1.0
2022-03-16 12:07:49,309 INFO: Matching 2317 image pairs

I don’t see this error with resized images. Very strange!

[Gordon]

It’s not only M2P images, another DJI drone’s camera I ran through a couple of days ago (Crop = 0 but still crop the corner) had an altitude over 200km below ground.

Where is it getting these numbers from?

The set of images I took this afternoon were between 8 and 25m above ground, as it says in the headers, and just under 650m ASL, also in the header, so how is this determined, as it bears no relationship to EXIF altitudes?

2022-04-02 14:08:24,373 INFO: Altitude for orientation based matching 1.8053909085861939

[joanlyq]

I’ve seen this in almost all DJI drone I’ve used. I never trust it’s GPS altitude, but only look at it’s relative altitude.

I don’t really know why, but it happens. But I never had difficulty orthomosaicing because of this