3.3 Active Headwall Properties

Using the SfM-MVS point clouds for 2016, 2017 and 2018, active headwalls were digitized and categorized based on the ice thickness (IT), overburden thickness (OT) and proportion of ice (PI) visible from their exposures. This resulted in three sperate headwall lines in each year, amounting to nine in total. An example of the headwall positions in each year and extra detail of the measurements from a small section is provided in (Figure 4). Transects were added at 5 m intervals, perpendicular to the direction of HWR, where headwall property measurements and retreat rates were measured. Transects that contained no clear exposures of ice in any of the three years were excluded from the numerical analysis and correlations. This reduced the number of usable transects from 163 to 128.