Improved correction methods for measuring altitude by Radar and Barometer

Abstract

Geometric altitude of air targets may be found from radar or barometric measurement. However, radar rays are affected by changes in refractive index gradients which result in non-normal bending of rays. Similarly, precision of barometric altitude is affected by the atmospheric deviation away from barometer standard calibrated sea level temperature and pressure, and deviation away from standard temperature lapse rate. Together these effects may lead to hundreds of meters of difference in match between barometric geometric height and radar geometric height. In this report we are proposing two alternative altitude correction methods. Both methods are applied to pairs of ground radar and barometry altitude of civilian airplanes. The most promising of the methods relies on using the meteorological atmospheric forecasting model AROME Arctic. For several of our measurement series this procedure reduces averaged difference between barometric altitude and radar altitude from 400-700 meters down to about 100 meters.