This review is grounded entirely in the in-situ measurements compiled in Chapter 9 – Physical Properties of the Lunar Surface of the Lunar Sourcebook (Heiken et al., 1991), including Apollo and 
Lunokhod data. The proposed L1–L5 zoning framework does not imply uniformity; it explicitly 
incorporates the full documented variability of density, compressibility, and shear parameters across sites. The zoning is a structured translation of the measured range into conservative, design-ready strata for engineering applications under uncertainty, enabling contractors and mission planners to apply Apollo-era knowledge directly in modern design scenarios.
This work presents a forensic, data-driven re-examination of the Lunar Sourcebook, isolating and replotting each relevant dataset and interpreting them within a consistent geotechnical framework.