Terrain classification and CE-3 benchmark region. (a) Spatial distribution of the classified mare (blue) and highland (orange) units on the lunar disk using the GF-4 observation on 2018 July 25. (b) Histogram of B4 Lommel–Seeliger reduced reflectance (﹩{r}_{\mathrm{LS}}﹩) for all pixels and for the classified mare and highland subsets. (c) Geologic context of the CE-3 ROI. The geologic base map is modified from the United States Geological Survey (USGS) Unified Geologic Map of the Moon (C. M. Fortezzo et al. 2020).