Refraction influence analysis and investigations on automated elimination of refraction effects on geodetic measurements

Refraction effects are generally caused by an inhomogeneous propaga- tion medium for the optical beam and are recognized as today's major source of systematic errors in the precise optical determination of angles and distances. Be- cause meteorological point measurements do not deliver satisfactory correction val- ues, the investigation of alternative methods motivated the development of a disper- someter, a metrological solution with a very sophisticated instrumental set-up. Fur- thermore, the compensation of deterministic refraction effects basing on atmospheric scintillation is envisaged: Optical scintillation measurements with a scintillometer or with CCD-sensors yield line averaged turbulence parameters of the atmospheric surface layer, which can be used for determining the refractive index gradient. Be- cause CCD-sensors are implemented in today's high-end surveying instruments, automated on-board-solutions will be possible.