a pair of observations

abundant observations

adjustment of indirect observations

aircraft（-based） observations

altitude observations of a celestial body

Borehole strainmeter observations

carrier observations

clinical observations

Conjugate observations

Constellation occultation observations

Curative effect observations

cytological observations

decoding observations

Doppler weather radar observations

Dynamic observations

earth rock dam observations

Equilibrium balloon observations

Error of angular observations

error removed using dual frequency observations

field observations