Define true zenith distance n meridional zenith distance?

Answer 1

Defining true zenith distance is knowing the difference between Africa and south America.True zenith distance is associated with Greenwich line and meridional zenith distance is defined with the celestial equator which instructs the basin of south america. -AG

Answer 2

The true zenith distance is the angular distance between a celestial object and the observer's zenith, measured along the observer's vertical circle. The meridional zenith distance is the true zenith distance measured along the observer's meridian.