Map: 144 fingerprints, 7 walks over 3 stretches, 2 outings.

Each outing held out in turn, and its scans located from the other outings:

                                by networks  and by signal  signal, calibrated  settling ties choosing the path  at a walking pace
  scans held out                        144            144                 144            144               144                144
  placed on the right stretch           136            139                 138            136               135                136
  placed across a mark                    8              5                   6              8                 9                  8
  landed on the wrong stretch             0              0                   0              0                 0                  0
  not on the map                          0              0                   0              0                 0                  0
  mean error, of a stretch              18%            17%                 17%            18%               18%                17%
  median error, of a stretch            17%            17%                 17%            17%               17%                18%
  mean error in metres                 23 m           23 m                23 m           23 m              24 m               23 m
  median error in metres               21 m           22 m                22 m           21 m              22 m               23 m
  pulled in, near a corner            +12 m          +14 m               +13 m          +12 m             +12 m              +11 m
  moved faster than a walk        22 of 129       9 of 132            9 of 131      22 of 129         23 of 128           6 of 129

  A scan that landed on the wrong stretch is not a small error, it is a different street,
  so it is counted apart rather than averaged into the distances. One placed across a mark
  is on the stretch next door, a few metres past the mark the two share, and its error is
  measured through that mark. Signal, calibrated compares levels after correcting the card
  by what it learns on the run, as --locate --watch --match signal does: here it corrected
  100 of 144 scans, by +0.5 dB. Settling ties places each scan with the scans before it
  breaking a tie between two stretches. Choosing the path takes the likeliest path through
  them, which can overrule the scan itself. At a walking pace settles ties and keeps each
  answer's place along the stretch to a walk's speed, as --locate --watch does. Pulled in,
  near a corner is how far the answers to scans taken within a fifth of a block of a
  corner landed towards the middle of the block, on average, and negative past the corner,
  into the block next door. Moved faster than a walk counts the steps between two answers
  in a row on the right stretch that nobody walks in the seconds between them.
