Extended Data Fig. 7: Odour velocity and concentration gradients provide complementary directional information in complex plumes.

a, Vector field of the negative gradient of odour concentration \(-\nabla c\), averaged over the full simulation (compare to Fig. 6c in the main text). Gradients contain strong lateral components near the odour source. b, Time course of an estimate of the direction of odour motion \({\theta }_{{\rm{odor}}}={\tan }^{-1}({{\bf{v}}}_{y,{\rm{odor}}},{{\bf{v}}}_{x,{\rm{odor}}})\) at the centre of the boxed regions in Fig. 6a, determined by averaging all detectable \(\theta \) in the past t seconds. Error bars are found by repeating this for 16 different 10 s time windows throughout the simulation, and taking the average and standard deviation over these 16 samples – these correspond to the mean and standard error of the mean. Dots indicate the time needed to distinguish the direction of odour motion from \({0}^{\text{o}}\) (downwind) with a 68% confidence level for the 3 regions. c, Heatmap of time taken to distinguish the direction of odour motion from \({0}^{\text{o}}\) to within 68% confidence for fixed locations throughout plume. Black values include the possibility that the odour motion direction is not distinguishable from downwind no matter how long one samples.