Hi there,
Leonardo, who is our ST-Sim expert, is out of office until Tuesday next week.
According to our ST-Sim documentation, the spread distance is accumulated over timesteps with the origin point at the center of a cell. Here’s the corresponding excerpt from the documentation:
“Each timestep the model samples from the Spread Distribution for each neighbor of each cell that is contagious and tracks the accumulated spread distance in that direction. Once the accumulated spread distance exceeds the center to center distance between neighbors, the model will apply a transition from the contagious transition group to the target neighbor.”
Here’s a link to the Transition Spread Distribution documentation: https://docs.stsim.net/reference/prop_transition_spread_dist.html
I will confirm with Leonardo when he is back in office next week if I missed any details,
Sarah