The landscape is the world the bug navigates — a 2D magnetic field environment that models the Earth’s geomagnetic field plus geological anomalies. The uniform geomagnetic field provides the compass signal; the anomalies test the compass’s robustness.
Geomagnetic Background
The background field is characterised by:
- Declination — the angle between geographic and magnetic north
- Inclination — the dip angle (how steeply field lines plunge into the Earth)
- Total intensity — ~50 μT at mid-latitudes
An inclination compass (like the radical-pair mechanism) measures the angle between the field and the local vertical, not the field direction. This means it cannot distinguish north from south — it detects the axis, not the polarity.
Anomaly Types
| Type | Model | Physical Origin |
|---|---|---|
| Gaussian | Localised intensity perturbation | Ore body, volcanic intrusion |
| Dipole | 1/r³ decay, full vector field | Magnetised rock, buried object |
| Fault | Step function in inclination | Geological contact, fault line |
| Gradient | Linear variation across domain | Regional tectonic structure |
Anomalies can reach hundreds of nanotesla — significant compared to the few-percent anisotropy that the compass relies on. The model reveals that same-frame bias cancellation (subtracting a reference channel) provides robust anomaly rejection up to ~500 nT.
Source: modules/mayajiva/experiment/landscape.py (248 lines), src/core/landscape.hpp (164 lines)