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Settle the 1985 bc850xx family just under the near_upper stratum (1,534 frames, likely scale_wrong) #78

Description

@NewGraphEnvironment

What changes if we do it: about 1,500 film frames on nine 1985 rolls stop being drawn at nominal scale if, as looks likely, their scale is the wrong field — the same scale_wrong class #72 tabled. What happens if we never do: they stay on the nominal fallback at roughly 1/r of their true width (r ≈ 1.6–1.8), which is the documented behaviour for an unmeasured roll-height, and the note's bound keeps saying so.

Problem

#72 settled the r ≈ 2 mass per roll-height, but only over the sweep's near_upper stratum (2 < r above sea level ≤ 3). Just under its floor sits a family it never sampled:

  • 1,534 frames on nine 1985 rolls (bc85063, bc85078, bc85080–bc85083, bc85089–bc85091) at 6,096 m (20,000 ft), 305 mm, 1:10000. Ratio above sea level 6096 / 3050 = 1.999, against the sample's lowest 2.025.
  • Two of them surfaced among the random draws beyond the band: bc85083 r 1.73, bc85090 r 1.63.
  • The tabled bc85079–bc85081 roll-heights are the same camera, lens and scale at 21,000 ft, and the pages read in Half the r≈2 mass is a wrong scale, not a mislabelled lens, and the fallback draws it at half width #72 log 20,000 ft for bc85080 85-145 and bc85081 81-97 — the height these frames carry.

So they are likely scale_wrong (true scale nearer 1:17000), and unmeasured.

What would settle it

The #72 route, extended to this stratum:

  • Sample MRDEM under the family's frames (they are not in inst/extdata/flying_height_sweep.csv) — or add a stratum to data-raw/height_calibrate-flying_height_slip.R for 1.6 < r_asl ≤ 2.
  • Fetch and transcribe the remaining rolls' logbook pages, blind. bc85080 and bc85081 are already in data-raw/flying_height_logbooks.csv, including their 20,000 ft strips.
  • Run them through settle() under tail = "near_upper" with the same rule: logbook factor 1, no legible lens conflict, and spacing that fits the reported height and rejects nominal.

Before starting, check whether the stratum holds other families. The "1.6 < r_asl ≤ 2" band was never sampled at all, so this family is the largest known group, not necessarily the largest.

See inst/notes/terrain-correction.md, "The r ≈ 2 mass is two defects", Bound.

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