Blast Movement Monitoring (BMM) places electromagnetic markers inside an ore block before blasting, then relocates them afterward to measure how far the rock actually moved — the raw material for shifting the dig-boundary polygon so the excavator digs ore, not waste.
Holes fire column-by-column, retreating from the free face at the left edge. Each block's true displacement is a simplified empirical model:
base = k · (energy/100) · (spacing_ref / spacing)
relief(c) = 1 − 0.55 · c / (cols − 1)
scatter = 0.15 + |delay − 25ms| / 100 · 1.1 (rad)
Δx = −base · relief(c) · cos(θ), θ ~ U(−scatter, scatter)
Δy = base · relief(c) · sin(θ)
Only marker blocks report an exact displacement; every other block's estimate is reconstructed by inverse-distance-weighted interpolation from the nearest markers. Boundary accuracy compares that reconstruction against the true field — with too few markers the estimate drifts, which is the entire reason BMM programs tune marker density against cost.