{
  "version": "2026-09-23.3",
  "units": "metres, seconds, kilograms; energy MJ",
  "coordinate_system": {
    "x": "along main bridge SW to NE, bearing N44deg53minE",
    "y": "NW/upstream normal to bridge",
    "z": "up",
    "three_mapping": "(x,z,-y)"
  },
  "identity": {
    "key": "1977 continuous steel through-truss original bridge, not replacement bridge",
    "ship": "Parametric Dali teaching exterior, not scanned geometry or exact stow plan",
    "lixin": "Dimensioned 3D T-frame/cantilever/suspended-span model plus separate navigation-width diagram; detailed evidence in lixinsha-evidence.json",
    "brooklyn": "Metric ship-height comparison, not full bridge elevation or AIS replay"
  },
  "sourced_dimensions": [
    {
      "quantity": "Key central bearing span",
      "m": 365.76,
      "source": "K2 PDF21; K3 PDF19",
      "original": "1200 ft"
    },
    {
      "quantity": "Key each side bearing span",
      "m": 219.9132,
      "source": "K3 PDF19, K2 approximately722ft",
      "original": "721.5 ft"
    },
    {
      "quantity": "Key three-span total",
      "m": 805.5864,
      "source": "K2 PDF21; K3 PDF19",
      "original": "2643 ft"
    },
    {
      "quantity": "Key deck overall width",
      "m": 18.6436,
      "source": "K2 PDF10",
      "original": "61ft2in"
    },
    {
      "quantity": "Key curb-to-curb width",
      "m": 17.6784,
      "source": "K2 PDF10",
      "original": "58ft"
    },
    {
      "quantity": "navigation channel width",
      "m": 213.36,
      "source": "K1 printed60",
      "original": "700ft"
    },
    {
      "quantity": "Dali overall length",
      "m": 299.9,
      "source": "K1 printed78 Table2"
    },
    {
      "quantity": "Dali maximum breadth",
      "m": 48.2,
      "source": "K1 printed78 Table2"
    },
    {
      "quantity": "Dali departure draft",
      "m": 12.15,
      "source": "K1 departure particulars; Table2 rounds casualty draft to12.2"
    },
    {
      "quantity": "Dali departure displacement",
      "kg": 112383000,
      "source": "K1 departure loading; NOT GT and NOT DWT"
    },
    {
      "quantity": "reported contact speed",
      "knots": 6.4,
      "m_per_s": 3.292444444444445,
      "source": "K1 printed47"
    },
    {
      "quantity": "dolphin cap diameter",
      "m": 8.5344,
      "source": "K1 printed65 Fig28",
      "original": "28ft"
    },
    {
      "quantity": "Lixinsha approved side navigation clear width",
      "m": 49.35,
      "source": "L1",
      "note": "not bearing spacing or hanging span length"
    },
    {
      "quantity": "Cuauhtemoc overall length",
      "m": 90.5,
      "source": "B2"
    },
    {
      "quantity": "Cuauhtemoc beam",
      "m": 12,
      "source": "B2; not displayed in side SVG"
    },
    {
      "quantity": "Cuauhtemoc reported air draft",
      "m": 48.2,
      "source": "B1 preliminary, waterline to highest point"
    },
    {
      "quantity": "Brooklyn MHW clearance comparison",
      "m": 38.7,
      "source": "B1 citing US Coast Pilot; not site-specific local collision clearance"
    },
    {
      "quantity": "Lixinsha main spans",
      "m": [
        55,
        85,
        55
      ],
      "source": "L3"
    },
    {
      "quantity": "Lixinsha suspended span",
      "m": 25,
      "source": "L3"
    },
    {
      "quantity": "Lixinsha bridge width",
      "m": 9.8,
      "source": "L3"
    }
  ],
  "assumptions": [
    "Key truss chords and diagonals follow the recognizable continuous-truss outline of K1 Fig17; panel counts and member sections are teaching geometry, not as-built sections.",
    "Key pier inclined-column details, head beam, and footing dimensions are simplified. Piers are not a calibrated contact model. The 1100ft clear opening in the source is not inferred from these simplified members.",
    "Key crest profile is smoothly interpolated using K2 vertical alignment; conversion of historical deck elevation datum to MHW not established, so no clearance clearance-engineering calculation is performed on mesh.",
    "Ship hull loft uses sourced length, breadth and draft. Deck height10.5m, two superstructure heights/positions and container distribution are exterior teaching assumptions informed by K1Fig41.",
    "Relative ship angle -112deg follows K1Fig17 orientation and late approach heading156.6deg at0127:46 (K1 printed46); not asserted as exact impact heading. Approach interpolation is not AIS replay.",
    "Four dolphins positioned approximately from K1Fig30. They are not an impenetrable wall and were not hit. The route geometry is checked for clearance from their cylinder envelopes.",
    "Banks only provide orientation outside central cropped bridge; they are not a surveyed coastline. Three short north approach spans are simplified context, not exact span20-22 geometry.",
    "Lixinsha planar boat width8-24m and illustrated length28.1m are classroom variables, not Lianghui688 dimensions. Only49.35m and selected width use the plane scale.",
    "Brooklyn SVG side outline including bowsprit spans90.5m. Mainmast top48.2m; other mast heights46/43.5m and detailed rig positions are illustrative. All sails stowed. Local platform geometry is illustrative.",
    "Brooklyn tide slider -2..2m relativeMHW is hypothetical. Vertical values compare referenced clearance and air draft, not reconstructed casualty tide.",
    "Lixinsha 3D uses sourced 55+85+55m main spans, 25m suspended spans and9.8m width; local sections, bearing sizes, pier tilts, ship65m length and debris are teaching assumptions. See lixinsha-evidence.json."
  ],
  "process": {
    "method": "manual staged mesh transforms and SVG interpolation, no FEM/contact/fluid/ fracture solve",
    "observed_key_timestamps_EDT": [
      "01:29:09 contact",
      "01:29:15 span18begins",
      "01:29:22 pier17collapses",
      "01:29:24 span20",
      "01:29:27 span21",
      "01:29:28 span22"
    ],
    "timeline_source": "K1 AppendixC printed226 PDF228",
    "animation_clock": "Key corrected elapsed seconds relative01:29:09 EDT, range -30..24; selectable0.25/0.5/1 speed. Independent floating time, range input only displays state. Pose interpolation remains illustrative."
  },
  "energy_model": {
    "formula": "E=0.5*m*(v_kn*1852/3600)^2",
    "mass_kg": 112383000,
    "not": "not pier force, not absorbed energy, not a collision design check",
    "GT": "95128 GT is volume-derived tonnage, excluded from mass computation"
  },
  "component_manifest": {
    "bridge": [
      "paired truss planes",
      "upper/lower chords",
      "diagonals",
      "floorbeams",
      "road barriers and lane marks",
      "four main support piers",
      "attached fenders",
      "four detached dolphins"
    ],
    "ship": [
      "metric lofted hull",
      "red antifouling bottom",
      "forecastle",
      "container stacks",
      "forward accommodation and bridge wings",
      "aft engine casing/funnel",
      "lifeboats",
      "mooring deck",
      "rails and masts"
    ],
    "controls": [
      "Key corrected-time slider, source-frame jumps, playback and video manual-contact synchronization",
      "NRP-like fixed view/overview/plan/elevation/pier/ship/section",
      "energy slider",
      "Lixinsha3Doverview/support/section and2D navigation experiment",
      "Brooklyn tide/contact",
      "14dialogue cues"
    ]
  },
  "key_collapse_contract": "key-collapse-contract.json",
  "key_motion_identity": "Source-constrained observation animation, not calibrated collapse/contact dynamics and not an exact frame-for-frame reconstruction",
  "key_camera": "Approximate NRP-like fixed view; not calibrated original camera",
  "lixinsha_evidence": "lixinsha-evidence.json"
}