Sherman S.C. Wu H. J. Moore 1973 Lunar slope-frequency distributions obtained by photogrammetric techniques are compared with results from the bistatic-radar investigations of the Apollo 14, 15, and 16 missions (refs. 33-16, 33-17, and 33-32) and of Explorer 35 (ref. 33-27). Algebraic standard deviations of slope-frequency distributions from photogrammetric data are equivalent to rms slopes of slope-frequency distributions from bistatic-radar data. Photogrammetrically derived algebraic standard deviations of the distributions are often larger than those obtained by the radar (ref. 33-25) when photogrammetric results at 25-, 200-, and 500-m slope lengths are compared with rms slope estimates from Apollo S-band (13-cm wavelength), Apollo VHF (1.16-m wavelength), and Explorer 35 (2.2-m wavelength) radar. application/pdf en National Aeronautics and Science Program Remote sensing and photogrammetric studies: Appendix to Part C: effect of photogrammetric reading error on slope-frequency distributions chapter