scanned in laboratory was compared with intensities extracted from scans made on the actual beach (Fig. 12) when the surface sand was dry. After correcting the distance effect, the field and laboratory measurements agree quite well. In Fig. 12, these two are compared with the incidence angle function of a 30% reflecting tarp, a target with approximately similar brightness to that of Kivenlahti sand. The results are similar to those obtained for Spectralon in Section 3.3, which points out that laboratory-derived results could be used to correct field measured TLS after the distance effect has been corrected. The sand data appears more scattered than that measured for the Spectralon plate. This is often the case with ‘real-world’ data, but it might also indicate a minor effect from the surface macro topography or roughness, similar to that of the Assuan sand (Fig. 2).