Concept

Loop closure — where it appears

Recognising that a later picture in a sequence sees what an earlier one saw, and adding those shared points to the adjustment. It gives the cameras near the join a short route back to the start; it fixes directions there and cannot fix a scale carried round the loop.

Named by 2 essays across one field — each of them below, with the objects they name alongside it.

Closing a loop mends its ends

Twenty-four cameras walked once round a ring of walls, every mark read to a pixel. Recognising the twenty-two points seen at both ends makes the last camera six and a half times better placed relative to the first — and the worst camera, across the ring, only a fifth better. A closure mends the ends of a walk and barely touches its far side.

manyviews · Drift

A loop's far side is a length

The worst camera on a closed loop of twenty-four is 411 mm from certain along the line from the start and 64 mm across it. A picture taken across the ring from the start tripod measures directions and moves the worst camera from 418 mm to 405. One distance measured across the ring to 10 mm moves it to 74, and a four-metre length measured on the start wall to 112. What the far side of a loop lacks is not a connection but a length.

manyviews · Drift

Named alongside it

The objects these essays reach for when they reach for this one.

bundle adjustment camera track Covariance Drift gauge freedom Control point scale ambiguity

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