{
  "model": "tunnel_skeleton.glb",
  "scope": "4745~5480 (4+745~5+480)",
  "units": "m",
  "origin_plan_xy": [
    151090.911,
    483688.46
  ],
  "sources": {
    "centreline": "C0060302-001 CA-ALGN-STSM (side-tick midpoint)",
    "road_grade_B": "C0060302-002 CR-TABL-TEX2 (계획고=노면)",
    "GL_A": "C0060302-002 CR-TABL-TEX2 (지반고)",
    "section": "C0060303-001 CS-TABL-TEX1/2, CS-CONC-MAJR, CS-EXCV"
  },
  "approximations": [
    "walls vertical down to road; invert not modelled",
    "lining band thickness at walls is radial-consistent but not as-built",
    "centreline and grade linearly interpolated between nodes",
    "superelevation sign convention assumed (z += S/100 * x, x = left of tangent)"
  ],
  "layers": [
    "lining_outer_R7282",
    "lining_inner_R6982",
    "excavation_R7402",
    "road_surface_계획고",
    "ground_GL_지반고"
  ],
  "open": [
    "4+700~4+745 and 5+480~5+500 excluded ([미확정])",
    "pattern zones (03-003~008) pending Task 5",
    "lining details (04-004~009) pending Task 6"
  ]
}