Using Vertical Aerial Photography to Estimate Mass Balance at a Point

摘要: The mass balance distribution over a 0.5 km2 area of the lower part South Cascade Glacier is obtained from remotely sensed measurements its geometry and velocity field two periods, 1992–93 1993–94. Vertical aerial photography late summer 1992, 1993, 1994 analyzed photogrammetrically to get surface topography on 100-meter square grid. known bed subtracted ice thickness, topographies are each other thickness change. Annual displacement vectors, determined at points where natural features could be tracked one year next, contoured by hand interpolated Assuming that follows Glen's flow law with exponent n = 3, 10% due sliding bed, scaled 0.82 average in vertical column. velocities combined thicknesses calculate flux divergence 46 gridpoints 100-m grid, it change balance. Use same control makes any systematic error photogrammetric coordinates temporally constant, so such has no effect estimate. Random assumed uncorrelated coordinate coordinate, point point, year; standard estimated 1 m, resulting differences about 1.5 m. A m nearly twice horizontal more than ten times has. Compared stake, balances too negative.