Comparison of geodetic and glaciological mass-balance techniques, Gulkana Glacier

Alaska, U.S.A., has been measured since 1966 by the glaciological method, in which seasonal balances are meas-ured at three index sites and extrapolated over large areas of the glacier. Systematic errors can accumulate linearly with time in this method. Therefore, the geodetic balance, in which errors are less time-dependent, was calculated for comparison with the glacio-logical method. Digital elevation models of the glacier in 1974, 1993 and 1999 were pre-pared using aerial photographs, and geodetic balances were computed, giving