Determination of a Hypsometer Performance Function from Airborne Data.
MASSACHUSETTS INST OF TECH CAMBRIDGE MEASUREMENT SYSTEMS LAB
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Integrated data from a vertical pendulous integrating gyro accelerometer were used to assess the altitude measuring performance of a hypsometer in an airborne gravimetric installation. Both gravity and Eotvos correction were assumed constant to simplify the integration process. The aircraft-autopilot short period about 0.044 Hz longitudinal mode dominates the altitude profile. The hypsometer recordings relative to the integrated accelerometer data showed lags between 2 and 3 seconds, and amplitude ratios between 0.4 and 0.9. A backlash nonlinearity of 3 feet amplitude would explain the varying amplitude ratio but only part of the lag 1 to 2 seconds. The auto-correlation and crosscorrelation functions were used in an attempt to examine the linear behavior of the hypsometer however, the spread of the data suggested that the nonlinearity was a very significant element in the instrument dynamics. Author