Methodology:

**Contours:**

Using ArcGIS Pro v3.5.2, contours were extracted at 250 metre intervals from a Digital Elevation Model (DEM) created from two published datasets. The DEM is primarily created from the 32m mosaic version of REMA v2 (Howat, Ian, et al., 2022, 'The Reference Elevation Model of Antarctica - Mosaics, Version 2', https://doi.org/10.7910/DVN/EBW8UC, Harvard Dataverse, V1, accessed June 2025) with some holes and artefacts filled with the Copernicus GLO-30 DEM (https://doi.org/10.5270/ESA-c5d3d65).

Once the contours were extracted, the lines were smoothed using a 500 m smoothing tolerance and all lines <0.4 km in length were deleted. Finally, the lines were split dependant on whether they fall on ice or rock ground. These changes were to enhance cartographic presentation of the data when styled on the 1:250 000 scale map.

The shapefile contains 3 fields: the main field is called 'contour' and contains the height in metres of each contour line. The heights are in respect of the EGM2008 geoid. There is also a field called 'rock_ice' which states whether the contour falls on ice or rocky ground, and a field called 'interval' which states 'yes' or 'no' depending on whether the contour is an interval of 1000 or not. The coordinate reference system of the data is WGS84 Antarctic Polar Stereographic, EPSG 3031.

**Spot heights:**

This file contains 355 spot heights for the Adelaide Island region, each point identified as a local high point with the height extracted from the 2 metre mosaic tiles of REMA v2 (Howat, Ian, et al., 2022, ''The Reference Elevation Model of Antarctica - Mosaics, Version 2', https://doi.org/10.7910/DVN/EBW8UC , Harvard Dataverse, V1, accessed June 2025.).

The spot heights were primarily extracted using the 'Spot Height Extractor' Plugin in QGIS (version 1.1 - https://plugins.qgis.org/plugins/Spot-Height-Extractor-Plugin-main/ ), with extra heights extracted as deemed necessary to suit this region and scale of map. The 32 metre version tiles of REMA v2 were first used to identify the local high points, and the 2 metre tiles were then used to extract the exact high points.

Two files are available alongside the main REMA v2 elevation files, each indicating the accuracy of a local area: 'count' details the number of contributing DEMs, and 'mad' details the median absolute deviation of height values within the contributing DEMs. Details here: https://www.pgc.umn.edu/guides/stereo-derived-elevation-models/pgc-dem-products-arcticdem-rema-and-earthdem/. These figures are useful for assessing the confidence of individual heights that were extracted, with a lower mad value indicating potentially higher accuracy. Therefore the necessary mad and count .tif files were downloaded, and the values for each height were extracted.

Finally, a field for place name was added to the resultant shapefile, where the spot height appeared to be associated with a known place name in the British Antarctic Territory gazetteer, accessed September 2025 (https://apc.antarctica.ac.uk/ ). Where a height was not clearly identified with a place name, the field was left empty.

The spot heights dataset contains the following attributes:

* 'msl_egm08' - the height in meters of each point above mean sea level, calculated in respect of EGM08 geoid.

* 'hae_wgs84' - the height in meters of each point above ellipsoid, calculated in respect of WGS84 ellipsoid.

* 'qa_count' - the number of contributing DEMs to the REMA v2 tiles

* 'qa_mad' - the'median absolute deviation in meters of contributing DEMs to the REMA v2 tiles

* 'name' - the associated place name for each point, if a name is present

The coordinate reference system of the data is WGS84 Antarctic Polar Stereographic, EPSG 3031.

**Lakes:**

The lakes in this dataset have been digitised from Sentinel-2 satellite imagery (Copernicus Sentinel d...(10)

Data collection:

ArcGIS Pro (version 3.5.2)

QGIS (version 3.34.7)

QGIS Spot Height Extractor plugin version 1.1

Data quality:

All data is subject to error and known potential errors have been detailed in the lineage statements. Elevation data accuracy statements can be seen in the source data publications. The lakes have been interpreted from satellite imagery using the dataset creator's best knowledge of the region and available data.