## 2 Materials and Methods
### Remote Sensing and Spatial Data  
Based on the review of available databases (Section 1.2), the seven periods have been chosen for the study of the fluctuation of glacial retreat rates. Due to the limited availability of the data, it was not possible in each case to determine equal or approximate intervals. **Year 1956. ** Aerial photographs taken in 1956 by the Falkland Island and Dependencies Aerial Survey Expedition were the earliest available sources of spatial information for ASPA-128. These  
Figure 3: The detection accuracy of the marginal zone of the Tower glacier. (**A**) the Landsat image with a resolution of 30 m; (**B**) the image of Normalised Difference Snow Index (NDSI) with a resolution of 30 m; (**C**) the image of pan-Normalised Difference Snow Index (panNDSI) with a resolution of 15 m; (**D**) the Planet satellite image with a resolution of 3 m; (**E**) the margin zone buffer with a width of 30 m; (**F**) the accuracy of ice border detection. photos were scanned at a 600 DPI resolution and calibrated using ground control points (GCP) with a calibration accuracy of 0.5 m. Due to the presence of snow cover, only fragments of the Baranowski and Ecology glacier fronts were mapped (Figure 4). **Year 1979. ** In the subsequent years, a number of cartographic product extents were published. Aerial photographs taken during the summer of 1978/79 were used to create the detailed 'Orthophotomap of ASPA-128 scale 1:10,000', which illustrates the glacier positions during the Antarctic summer of 1978/1979 [26]. The map was made based on the selection of fifteen aerial photos taken on 6 February 1979 with an AFA/BAF camera (210 mm focal lens) and subsequently scanned at a 600 DPI resolution. The photos were rectified according to the ground control points, which were obtained by the GPS survey conducted in 2007. For the complete orthorectification process, the digital elevation model was used. The DEM was interpolated based on set elevation points  
2007. After interpolation, the DEM was corrected to the elevation state in 1979 by the analysis-significant differences, which are visible by comparing the ice elevation in 1979 and 2007. As a result, the raster resolution is 0.3 m and the accuracy is 2 m.  
**Year 1989. ** The next map of ASPA-128 used in this study was the 'Map of Admiralty Bay scale 1:50,000' [33]. The map illustrates glacier fronts in 1989. Archival sketches and remarks on more detailed scales created by [PERSON] using theodolite measurements were used to improve the overall accuracy. These materials allow for the recognition of glacier fronts with a 5-10 m accuracy. **Year 2001. ** In 2001, the first differential GPS surveys of the ASPA-128 recorded glacier front positions; the measurements were repeated in 2007 [26; 34]. The field surveys (in 2001) were carried out using dual-frequency Ashtech Z-12 GPS receivers. Direct mapping included two stages: a dynamic mapping of glacier fronts and static measurements for the GCP points that were used for the ortho-rectification of archival aerial photographs. **Year 2007. ** In 2007, DGPS measurements were carried out using MLR SP 24 XC GPS receivers. The determination of glacier margins from the 2001 and 2007 field-based GPS surveys had an instrument accuracy of 1-2 m and an accuracy of field measurements of 1-2 m. Track logs along the glacier terminus were recorded at the end of the austral summer when no snow cover was present. **Year 2011. ** Glacier front positions in 2011 were mapped on Google Earth(tm) (GeoEye-1, DigitalGlobe(tm)) satellite image from 2 February 2011), which were rectified and calibrated to our previous maps using the DGPS points. The accuracy of the glacier extents in 2011 was 2 m.  
**Year 2018. ** The most current satellite data used in this work comes from 2018. Two PlanetScope(tm) images were obtained with a ground resolution of 3 m. The first picture with very good quality (visible sharp separation between snow-covered glacier-ice and ground) comes from 13 February. The second one was taken on 10 March.