An Improved Intersection Method for Positioning and Its Application to Dalk Glacier, East Antarctica

Abstract

Stake measurement is a significant ground-observation method used to monitor glacier dynamics in the cryosphere and validate the reliability of remotely sensed investigations. However, some stake observation records obtained by total stations have not been efficiently utilized via the classic forward intersection method. The forward intersection method requires a pair of cognominal observation records and cannot function if stakes are only observed from one control point at a stake measurement, which commonly occurs in measurements. Therefore, we propose an improved intersection method that combines stake trajectories and sightlines, the trajectory-sightline intersection method, which requires only a single observation record. In the processing of stake identification, location and elevation from the trajectory-sightline intersection method are constrained by the velocity and surface altitude of the glacier. Then, the trajectory-sightline intersection method is applied to the stake measurement of Dalk Glacier in East Antarctica. The results show that the trajectory-sightline intersection method extracted an additional 44 intersections, thus increasing the data utilization ratio by 20.35%. Moreover, leave-p-out cross-validation indicated that the trajectory-sightline intersection method, with an average offset of 0.88±0.54 m in the horizontal position and 0.26±0.12 m at the elevation, has similar accuracy to the differential global positioning system (DGPS) applied to Livingston Island. The ice flow velocities of Dalk Glacier calculated from trajectory-sightline intersections agree with those from forward intersections (the mean velocity difference is 0.47 m·year−1). Therefore, the trajectory-sightline intersection method is an effective method for improving data utilization and obtaining stake locations and glacier velocities.