Byrd Glacier Historical Air Photo DEM 10m v1

This dataset is comprised of two DEMs (10 m spatial resolution) that were generated from aerial images collected in December 1978 and January 1979 over Byrd Glacier, East Antarctica. The air photos were initially manually processed in 1980 (Brecher, 1982) and then mislaid for 36 years until eventually found in the basement of the USGS Reston Branch Library in 2016. The images were digitized by the USGS EROS Center at 1,000 dpi and are available from https://earthexplorer.usgs.gov/. The exact images used in the processing may be found in the Supplemental Information from Child et al., (submitted). The elevations were estimated using opensource structure-from-motion (SfM) photogrammetry software called MicMac (https://github.com/micmacIGN) with ground control manually extracted from the Regional Elevation Model of Antarctica (http://data.pgc.umn.edu/elev/dem/setsm/REMA/geocell/v1.0/2m/). The DEMs are projected horizontally to WGS84 Polar Stereographic and vertically to the WGS84 ellipsoid. Both DEMs have been registered to in situ GPS (https://www.usap-dc.org/view/project/p0000319) from exposed bedrock, but only three GPS site data are available. The vertical error of the GPS data is ~2-5 cm. It is recommended that a more spatially expansive registration should be carried out first before any analysis be conducted. The root mean square error of the December 1978 DEM after registration is 0.50 m and 2.30 m for the January 1979.

Brecher, H.H., 1982. Photographic determination of surface velocities and elevations on Byrd Glacier. Antarctic Journal 17, 79–81.

本数据集包含两景空间分辨率为10米的数字高程模型（DEM, Digital Elevation Model），其数据由1978年12月及1979年1月采集的航拍影像生成，覆盖区域为南极东部的伯德冰川（Byrd Glacier）。该航空照片最初于1980年由人工处理（Brecher, 1982），之后被错放并遗失长达36年，直至2016年才在美国地质调查局（USGS, United States Geological Survey）雷斯顿分馆图书馆的地下室中被重新发现。

这些影像由美国地质调查局地球资源观测与科学中心（USGS EROS Center）以1000dpi的分辨率完成数字化，可通过https://earthexplorer.usgs.gov/获取。本次处理所用的具体影像可参考Child等人（已投稿）的补充材料。

高程数据通过开源的运动恢复结构（SfM, Structure from Motion）摄影测量软件MicMac（https://github.com/micmacIGN）估算得到，地面控制点则从南极区域高程模型（REMA, Regional Elevation Model of Antarctica，http://data.pgc.umn.edu/elev/dem/setsm/REMA/geocell/v1.0/2m/）中手动提取。

两景DEM均采用WGS84极地方向横轴墨卡托投影（WGS84 Polar Stereographic）进行水平基准投影，垂直基准采用WGS84椭球体。二者均已通过暴露基岩的原位全球定位系统（GPS, Global Positioning System，https://www.usap-dc.org/view/project/p0000319）完成配准，但仅可获取3个GPS站点的数据，该GPS数据的垂直误差约为2至5厘米。建议在开展任何分析前，先进行空间覆盖范围更广的配准操作。配准完成后，1978年12月生成的DEM均方根误差为0.50米，1979年1月生成的DEM均方根误差为2.30米。

Brecher, H.H., 1982. 伯德冰川表面流速与高程的摄影测量测定. 《南极学报》17卷，79–81页。