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Conventional photogrammetry gives an 'up to scale' model, i.e. the scale is arbitrary and needs to set later to match reality. This is because a real cow far aw

Conventional photogrammetry gives an 'up to scale' model, i.e. the scale is arbitrary and needs to set later to match reality. This is because a real cow far away and a toy cow close up look the same in pictures. You can supplement images with lidar, stereo images, or IMU odometry to capture true scale information at the SfM stage to get (approximately) scale-correct models. Alternatively you can learn what the real world tends to look like and estimate absolute depth from images alone, if you have enough data. This might be defeated by toy cows and doll houses, but work for some applications.

CyberDildonics 3y ago
gives an 'up to scale' model, This is not a term that makes sense. It makes a model, there is no sense in having it scaled in any way except for being correct. Saying 'up to scale' is like saying 'feet running' or 'mouth eating' or 'face talking'. the scale is arbitrary Only if you don't measure anything. If you have the camera correct and know how high something is or just know some depth or distances photogrametry makes an accurate model. 'Scale model' is a term from when scaling the model down made it easier to make. In the computer, it just means it isn't accurate.
- robotresearcher 3y ago
  It's actually the technical term that is used in this context. It's used when you don't know the scale. You can estimate all the geometry 'up to' but not including a scale term. > and know how high something is or just know some depth or distances There you go: you just added in some extra information to constrain the scale estimate as I described.
  - robotresearcher 3y ago
    In the cow vs. toy cow example, you get a 3D model of a cow, but you don't know its absolute size. If you ALSO know that the cow is 2m long, or 3m away, you can infer the scaling factor for the geometry you estimated using pixels and camera intrinsics.

CyberDildonics 3y ago

gives an 'up to scale' model, This is not a term that makes sense. It makes a model, there is no sense in having it scaled in any way except for being correct. Saying 'up to scale' is like saying 'feet running' or 'mouth eating' or 'face talking'. the scale is arbitrary Only if you don't measure anything. If you have the camera correct and know how high something is or just know some depth or distances photogrametry makes an accurate model. 'Scale model' is a term from when scaling the model down made it easier to make. In the computer, it just means it isn't accurate.

robotresearcher 3y ago
It's actually the technical term that is used in this context. It's used when you don't know the scale. You can estimate all the geometry 'up to' but not including a scale term. > and know how high something is or just know some depth or distances There you go: you just added in some extra information to constrain the scale estimate as I described.
- robotresearcher 3y ago
  In the cow vs. toy cow example, you get a 3D model of a cow, but you don't know its absolute size. If you ALSO know that the cow is 2m long, or 3m away, you can infer the scaling factor for the geometry you estimated using pixels and camera intrinsics.