Detection probabilities. Left column shows all the transects, right column shows transects subset to distances downwind from 750–2000 m. The detection probability as a function of leak rate (a, b) shows general increase in skill with leak rate but the relation is not strong. The number of transects in each leak rate bin (c, d), is shown to qualify (a, b). Detection probability as a function of wind speed shows a peak in skill near 2–3 m s^–1(e, f). Detection probability as a function of distance shows a peak >800 m (g, h). Detection probability as a function of Gaussian plume model enhancement shows a more complex relation (i, j). Detection probability as a function of drone elevation shows little relation (above ground level, AGL) (k, l). Plots e-j show points representing an equal number of transects, where divisible evenly. Plots k, l are split evenly across the range of values. DOI: https://doi.org/10.1525/elementa.379.f7