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.