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HKUST-Aerial-Robotics / VINS-Mobile

Monocular Visual-Inertial State Estimator on Mobile Phones
GNU General Public License v3.0
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Question about ProjectionFactor::sqrt_info #78

Open vonzy opened 7 years ago

vonzy commented 7 years ago

In VIN-Mobile, the ProjectionFactor::sqrt_info is set to FOCUS_LENGTH_X / 1.5 * Matrix2d::Identity(). It seems the sqrt_info should be two arbitrarily selected orthogonal bases, but why it should be set to the value FOCUS_LENGTH_X / 1.5 , could you please explain it?

vonzy commented 7 years ago

convert to pixel error? but why divided by 1.5? @PeiliangLi @qintony

PeiliangLi commented 7 years ago

sqrt_info is the sqrt of the information matrix, information matrix is the inverse of the covariance matrix. We set 1.5 as the visual measurement noise in the pixel plane.

vonzy commented 7 years ago

@PeiliangLi you mean the code assume pixel error is 1.5 pixel?

PeiliangLi commented 7 years ago

yes

vonzy commented 7 years ago

all right, thanks~ @PeiliangLi