In theory, Solution 2 captures emissions from all emitters upwind of the ux plane that were active within the transport time of the emissions. However, exceptions exist for ights that did not extend high enough to traverse exhaust plumes from compressor drivers (Facility C). Since the drone transects are fast, additional uncertainty exists for unsteady emission sources near the ux plane (e.g. intermittent gas pneumatics) or in cases where wind near a building may attenuate or recirculate emissions. Unfortunately, no data exist to quantify these uncertainties. Finally, as noted earlier, multiple ux planes within one facility require adjustments by Solution 2's analysts to avoid double-counting emissions. In this study we assume these corrections were perfect, and no emissions were transported through two ux planes without correction. (SI Section S-2.4)