Comparison between glacier ice velocities inferred from GPS and sequential satellite images

Abstract

ABSTRACT. Measurements derived from remote-sensing research and field surveys have provided new ice-velocity data for David Glacier--Drygalski Ice Tongue and Priestley and Reeves Glaciers, Antarctica. Average surface velocities were determined by tracking crevasses and other patterns moving with the ice in two sequential satellite images. Velocity measurements were made for different time intervals (1973-90, 1990-92, etc.) using images from various satellite sensors (Landsat 1 MSS, LandsatTM, SPOT XS ). In a study of the dynamics ofDavid Glacier-Drygalski Ice Tongue and Priestley and Reeves G laciers, global positioning system (GPS ) measurements were made between 1989 and 1994. A number of points were measured on each glacier: five points on David Glacier, three on Drygalski Ice Tongue, two on Reeves Glacier-Nansen Ice Sheet and two on Priestley Glacier. Comparison of the results from GPS data and feature-tracking in areas close to image tie-points shows that errors in measured average velocity from the featuretracking may be as little as ± 15-20 m a I. In areas far from tie-points, such as the outer part of Drygalski Ice Tonpue, comparison of the two types of measurements shows differences of about ± 70 m a -.

L-band scintillations and calibrated total electron content gradients over Brazil during the last solar maximum

“…Besides the ability to provide position with accuracy from few meters to few centimetres, or even millimetres, depending on the chosen technique, GNSS also allows one to study physical phenomena in different fields of Earth sciences (Shimada et al 1990;Bevis et al 1992;Frezzotti et al 1998;Blewitt et al 2006;Larson 2009).…”

Joint Geophysical Observations of Ice Stream Dynamics

“…GPS data collected during the 2005-06 austral summer reveal that the flow speed generally agrees with data collected between 1991 and 1994 by Frezzotti et al (1998): in particular, the horizontal velocity measured in 1991-1994 at point Da2 (1.51 m/day) located at S 75° 21' 45", E 162° 08' 58" is quite confirmed by the new GPS measurements carried out at point DRY1 eleven years later (Figure 9). …”

“…The UP-N and UP-S clusters count together 74 events occurring sparsely at the top of the icefall, in correspondence of the area where the ice flows fast (more than 500 m/y from Frezzotti et al 1998), the bedrock topography drops 300-400 m and the mean slope is around 60%-80% (Rignot 2002).…”

“…2) but, unfortunately, we don't have any direct GPS measurement available for the 2003-04 ice flow velocity. Frezzotti et al (1998) measured the mean ice speed between 1991 and 1994 some km downstream of ICF1 founding a slightly lower value of 1.39 m/day (their station Da4).…”

“…It has been shown that the use of GNSS instrumentations can be very useful for the measurement of glaciers movements (Hulbe and Whillans 1994;Frezzotti et al 1998;Doake et al 2002;Bindcshadler et al 2003;King and Aoki 2003;Legresy et al 2004) and it is one of the most reliable methods to monitor the position of selected points located on a glacier with high precision. Moving glaciers can also be monitored in a seismological perspective.…”