Structural watch · tilt & creep detectors

Creep watch & crane guard

A spare phone on a tripod becomes a sub-millimetre creep monitor on a cracked column, a shoring strut or a slab edge: four patches of the picture are tracked against the moment you armed it, tripod bumps are rejected by the phone's own motion sensors, 1 mm warns the safety officer and 2 mm fires the scene-wide ALL STOP. The crane guard reads boom angle from a phone strapped to the boom (or typed), works the radius, slab mass with snag shock, sling-leg tension, wind derating and outrigger bearing into a load-moment percentage, and paints the swing cone on the map. Planning aids — the structures specialist and the crane's certified LMI govern.

Incident

Creep watch

Camera & calibration

Target Standoff m Zoom × Lens HFOV °

Interval s

Lock the phone on a tripod (or wedge it), frame the crack or joint across the middle, start, let the image settle, then ARM. Patches with no texture are ignored; if fewer than two lock, move closer or pick a busier target.

Readings

Not armed.

Crane guard

Lift parameters

Crane position lat, lng Boom bearing ° Slew ± °

Creep: normalised cross-correlation on four 48-px patches with parabolic sub-pixel refinement (≈ ±0.08 px ≈ ±0.4 mm at 5 m, 2× zoom on the 640-px analysis frame — halve the standoff or raise the zoom for finer); mm/px = standoff ÷ focal length (focal = width ÷ 2·tan(HFOV/2)); frames during device motion (> 0.35 m/s² or 1.5 °/s) are discarded. Crane: R = L·cos θ + offset; rated = 0.75 × counterweight moment ÷ (R − outrigger half-span) capped by the chart max (ASME B30.5 75 % rule); slab = L·W·t × 2.45 t/m³ × 1.25 snag; T_leg = W ÷ (n·sin α); wind derate from 20 kn to the crane's limit; LMI = gross ÷ rated. Not engineering advice.