Description
The Fundamental Diagram (FD) is the empirical or analytical relationship between local pedestrian density and either walking speed or volumetric flow. Together, ρ–v and ρ–q curves summarise macroscopic crowd behaviour: free-flow at low density, congestion above a critical density, jamming and the "faster-is-slower" regime above that. In the thesis context, the FD is the bridge between BLE-derived ground-truth trajectories and CSI-derived density observations — it constrains the physics-informed model to obey conservation of pedestrians.
When it's used
- Calibrating
continuum-crowd-modelandsocial-force-modelparameters - Validating
crowd-flow-estimationoutputs against ground truth - Capacity analysis for indoor venues
- Regulariser inside physics-informed CSI inference
Limitations
- Strongly population-dependent (geography, age, culture)
- Anisotropy (uni- vs bi-directional flow) changes the curves
- Hard to fit at extreme densities without dedicated experiments