# Maximizing Apparent Velocity in a Camera's Frame

How should a drone move to maximize its apparent velocity in the frame of a camera? This Demonstration solves this problem for a drone that can move a distance in any direction.

### DETAILS

If a drone (represented as a particle) can move with equal velocity in any direction, the set of possible 3D coordinates after one time step is a 3D sphere. The image plane of a camera projects all 3D points into a 2D camera frame [1]. If the sphere is centered at with radius and camera focal length , then the optimal goal location for the drone is parameterized by the (latitude, longitude) pair :
,
.
If is , there are infinite solutions with .
The goal location is:
This projects onto the image plane at the point . Because is always negative, the drone decreases the distance in . Interestingly, the sphere projects into a 2D ellipse in the image plane. With equations given by [2], the ellipse is centered at
,
with
,
and
.
The focal length is 5 in this Demonstration.
Snapshot 1: , , and
Snapshot 2: 2D view when , , and
Snapshot 3: , , and with "show drone" turned off
Snapshot 4: 2D view when , , and with "show sphere" turned off
Snapshot 5: , , and
Snapshot 6: , , and with "show drone" turned off
Snapshot 7: 2D view when , , and
References
[1] M. W. Spong, S. Hutchinson and M. Vidyasagar, Robot Modeling and Control, Hoboken, NJ: John Wiley and Sons, 2006.
[2] D. Eberly. "Perspective Projection of an Ellipsoid." (Oct 30, 2018) www.geometrictools.com/Documentation/PerspectiveProjectionEllipsoid.pdf.

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