On the accuracy and interpretation of Dynasonde virtual height measurements

Accurate group height estimates can be performed using two independent methods in the Dynasonde. The conventional time of arrival (TOA) of the echo envelope is measured directly in 0.2‐km units, while echo phase values, measured to 4° over small (8 kHz) frequency intervals, permit application of the stationary phase principle. Both methods receive corrections in real time for echo amplitude variations. Comparisons of TOA and stationary‐phase measurements by several Dynasonde display formats suggest that dispersive effects can cause considerable group height errors by the TOA method, especially near penetration frequencies. This is confirmed by a computer simulation which yields the pulse envelope and gives information concerning the effect of dispersion on the echo phase.