Visual Plane
every picture states the point it is correct from
Series

Drift — the series

5 essays on one idea, from the one that introduces it to the one that assumes the rest.
  1. 0.30.50.7125×10⁻⁴0.0010.0020.0050.010.02how finely each point is read (px, log scale)worst camera-centre error, as a fraction of the track's mean radius (log)chained pairsadjusted togetheradjustment is 4.0–9.2× better6 views · identical observations

    A chain and an adjustment

    Composing pairwise poses along a sequence is supposed to drift. Measured over five links it wanders instead — one chain ends closer to the truth than its own worst link — and the real cost of chaining turns out to be something else entirely.

    part 2 · manyviews
  2. -200204060050100150link along the streetscale error relative to the first link (%)average 28.6 %16 streets · ties by mean of ratios · marks read to 1 pxspread after 199 links ±7.3 %

    A scale chain leans rather than wanders

    A camera driven 200 m along a street, each pair's scale handed to the next through the points they share. Across sixteen streets the scale does not spread the way a random walk would — 7.3 per cent after 199 links, where independent ties would give 108 — and its average leans by an amount the choice of average decides, from +28.6 per cent to −12.2.

    part 3 · manyviews
  3. 02004005101520camera round the loopcamera-centre standard deviation from the start (mm)left openclosedlast camera ×6.5 better · worst 20 % better24 cameras · marks read to 1 px

    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.

    part 4 · manyviews
  4. start, heldworst: 86 along, 64 acrossellipses ×12 · worst camera 112 mmloop closed

    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.

    part 5 · manyviews
  5. 0.050.10.250.51240200400length of the scale bar at the start (m, log scale)worst camera, along the line from the start (mm)open walkloop closedopen, no barclosed, no bara scale bar at the start, measured to 0.1 mmopen: flat from 0.5 m

    A scale bar is worth its ends, not its tape

    A length measured at the start of a walk round a ring pins the walk's scale — but only to the precision with which the pictures place the length's two ends, 3.4 mm here, whatever the tape says. Measured to a thirtieth of a millimetre or to three millimetres, a one-metre bar leaves the worst camera at the same 89 mm. So a short length is not a long one measured well: a bar under about 13 cm tells the walk less about its scale than the walk already knows. And on an open walk no length at the start does better than 214 mm, because what is left there is drift, not scale.

    part 6 · manyviews

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