ABSTRACTThis is the first (Paper I) of three companion papers focused respectively, on the estimates of the errors in ice thickness retrieved from pulsed ground-penetrating radar (GPR) data, on how to estimate the errors at the grid points of an ice-thickness DEM, and on how the latter errors, plus the boundary delineation errors, affect the ice-volume estimates. We here present a comprehensive analysis of the various errors involved in the computation of ice thickness from pulsed GPR data, assuming they have been properly migrated. We split the ice-thickness error into independent components that can be estimated separately. We consider, among others, the effects of the errors in radio-wave velocity and timing. A novel aspect is the estimate of the error in thickness due to the uncertainty in horizontal positioning of the GPR measurements, based on the local thickness gradient. Another novel contribution is the estimate of the horizontal positioning error of the GPR measurements due to the velocity of the GPR system while profiling, and the periods of GPS refreshing and GPR triggering. Their effects are particularly important for airborne profiling. We illustrate our methodology through a case study of Werenskioldbreen, Svalbard.