An apparatus measuring the temperature andor pressure of an exhaust gas plume from a supersonic military jet engine. The dummy metal fill formed above the gate electrode extends in the gate length direction with both ends thereof protruding from a region corresponding to the gate electrode. Using the reference sensor and the lead apparatus sensor, a distance parameter indicative of a distance between the reference and lead apparatus sensors is measured for each of the plurality of left heart locations. There is at least one water-collecting pocket along the side of the or each passage. The method is driven by a set of data preprocessing and model performance metrics subsystems that when applied to a raw data set, produce an optimal empirical model.