Homography from your own point pairs
Plane A is a pickleball court seen from above, in metres; plane B is a photograph of it. Each pair you click adds two equations to the DLT, and from four pairs on the lab solves for the homography and draws the whole court pushed from A into B, with the miss at every pair you gave it.
Try this
Load the measured corners, then add one pair on purpose in the wrong place: the whole court bends towards it, which is why the next step is RANSAC.
Frame 45000 of "2026.07.25 WD Open … (Gold Medal match)" by pickleball4you, CC BY 3.0.
Where this lab comes from
How to Compute a Homography from Four PointsLesson 3 of Image Alignment. Each point pair gives two linear equations in the nine entries of H, and the answer is the singular vector of the smallest singular value. Normalising the coordinates drops the condition number from 53,466 to 6.4, and on this court changes the answer by under 0.2 cm. What decides the error is where the pixels are: one pixel is 0.6 cm of court at the near baseline and 8.1 cm at the far one.
More in cameras and geometry
- Focus, aperture and depth of field — Move the subject and watch the focus plane and the blur follow.
- Four ways a fisheye maps angle to radius — Plot r(θ) for the classical designs against a fitted curve.
- The scene, and what the camera sees — Orbit a 3-D scene on the left; the pinhole view updates on the right.