A system for monitoring and determining plant output activity comprising: an imaging subsystem (100, 150, 200, 250, 300, 400, 500, 600) capable of imaging effluent plumes for thermal output with or without effluent compositional data from one or a plurality of stacks (114a-d, 164a-d, 214a-d), at an industrial facility and capturing image data associated therewith, said imaging subsystem comprising, one or a plurality of imaging units (110, 160a-d, 210, 260a-d) having one or a plurality of infrared detector cameras (404, 506a-d, 606a-d, 704) that are a thermal detector adapted to capture thermal data, with or without one or a plurality of effluent composition detectors adapted to capture data corresponding to the production of a given atomic species, molecular species, and/or class of molecular species from the effluent plumes and with a detector capable of converting incident light into an electronic signal for analysis; an analysis subsystem for processing (900, 1000, 1100) the thermal image data into plant output data comprising plant output activity and capacity utilisation with or without effluent compositional data of the industrial facility; characterised in that the one or plurality of imaging units are capable of imaging at a distance of between 25 metres to 10 kilometres within a clear line of sight to the one or plurality of stacks of the industrial facility, said system further comprising a data processing subsystem capable of performing the steps to i) extract pixels associated with an active region in the captured image, ii) determine which of the extracted pixels are on and have an intensity greater than a background or set threshold intensity and iii) apply correction factors for weather conditions to the active region on pixels after extraction, said correction factors determined from acquired effluent plume images accumulated over time or acquired under different weather conditions at constant plant output; wherein the corrected on pixels are processed into the plant output data prior to analysis. an imaging subsystem (100, 150, 200, 250, 300, 400, 500, 600) capable of imaging effluent plumes for thermal output with or without effluent compositional data from one or a plurality of stacks (114a-d, 164a-d, 214a-d), at an industrial facility and capturing image data associated therewith, said imaging subsystem comprising, one or a plurality of imaging units (110, 160a-d, 210, 260a-d) having one or a plurality of infrared detector cameras (404, 506a-d, 606a-d, 704) that are a thermal detector adapted to capture thermal data, with or without one or a plurality of effluent composition detectors adapted to capture data corresponding to the production of a given atomic species, molecular species, and/or class of molecular species from the effluent plumes and with a detector capable of converting incident light into an electronic signal for analysis; an analysis subsystem for processing (900, 1000, 1100) the thermal image data into plant output data comprising plant output activity and capacity utilisation with or without effluent compositional data of the industrial facility; characterised in that the one or plurality of imaging units are capable of imaging at a distance of between 25 metres to 10 kilometres within a clear line of sight to the one or plurality of stacks of the industrial facility, said system further comprising a data processing subsystem capable of performing the steps to i) extract pixels associated with an active region in the captured image, ii) determine which of the extracted pixels are on and have an intensity greater than a background or set threshold intensity and iii) apply correction factors for weather conditions to the active region on pixels after extraction, said correction factors determined from acquired effluent plume images accumulated over time or acquired under different weather conditions at constant plant output; wherein the corrected on pixels are processed into the plant output data prior to analysis.