Passive positioning through bathymetric correlation - match measured depth profiles with seafloor maps for covert navigation
About This Demo
Terrain-Aided Navigation (TAN) provides passive positioning by correlating real-time depth measurements
with a priori bathymetric maps. Unlike acoustic beacons, TAN is completely passive (no transmissions),
making it ideal for covert operations. Performance depends critically on terrain variability - flat
seafloors provide poor observability while rugged terrain enables accurate positioning.
Terrain Configuration
20 m
200 m
0.5 m
50 m
500 m
Terrain Presets
--
Peak Correlation
--
Position Error
--
Match Confidence
--
Terrain Gradient
Bathymetric Map & Vehicle Track
Depth Profile Correlation
Correlation Function
Position Solution Over Time
TAN Theory
Correlation Principle
TAN matches measured depth to map depth over a trajectory window:
zTAN = dmeasured - dmap(pINS)
TERCOM Algorithm
Position offset that maximizes correlation between measured and map depths:
Δp = argmaxδp Σ wi · (dmeas,i - dmap(pi + δp))²
Observability Requirements
Map resolution: 5-50m grid spacing (finer than position uncertainty)
Map vertical accuracy: < 1m RMS
Terrain gradient: > 10m relief per km for unique matching