Evaluation of Repeat Image Feature Tracking (RIFT) Software in Estimating Surface Ice Velocity Over Southwest Greenland

Abstract:

Observations of ice motion on the Greenland ice sheet are critical for understanding ice sheet mass balance and contribution to sea level rise, as well as predicting future changes. The development of interferometric synthetic aperture radar (InSAR) and optical-image-tracking methods has allowed us to remotely estimate surface ice velocities over large areas. In this study, we report results concerning the assessment and comparison of the outputs of two repeat image feature tracking (RIFT) software programs, namely, multiple-image/multiple-chip (MIMC 2.0) and Image GeoRectification and Feature Tracking (ImGRAFT). For our purpose, we focus on a southwestern portion of the Greenland ice sheet within the ablation zone. The RIFT algorithms use cross-correlation of variations in image intensity, such as surface texture, to match the images. The cross-correlation method produces a pixel displacement field, and finally a velocity field. Feature tracking is performed using pairs of the recently launched Landsat 8 as well as WorldView 2 (WV2) commercial imagery in monthly and yearly combinations. The outputs of the two RIFT tools are compared to annual ice-sheet-wide velocity maps obtained from Interferometric Synthetic Aperture Radar (InSAR) data from the RADARSAT-1 satellite.