GLORIA and Sea Beam data are processed together with a number of benefits. The Sea Beam data allow an improved slant- to ground-range projection of the imagery that results in less of the distortions, such as layover and foreshortening, that are produced when the seafloor is assumed to be flat. A calculation originally intended to quantify side scan sonar data has also been found to improve the images in an image enhancement sense. This calculation involves estimating the seafloor's backscatter strength from GLORIA side scan sonar data using a simple physical model and the characteristics of the GLORIA instrument. The backscatter strength is the ratio of backscattered to incident sonar intensity on the sea bottom, normalized to the surface area covered by the acoustic pulse. It is computed by correcting the GLORIA data for propagation losses, beam directivity pattern, time-varied amplifier gain and other factors. The calculation is improved by accounting for refraction in the water column and for some topographic effects using Sea Beam data. A GLORIA image from a mid-ocean ridge crest is shown to have a large 60-dB range that is due to the effect of the system response, such as the beam pattern, on the images. The corresponding image of the seafloor backscatter strength has an almost Gaussian distribution of picture element digital numbers with a narrow range, 20 dB, showing that most of the system effects have been removed. Cross sections through the backscatter strength image show flat trends superimposed with finer variations due to the seafloor geoloty. The conversion of GLORIA data into seafloor backscatter strength serves two purposes; it provides quantitative information that can be used to determine the likely causes of particular features in the images and it performs what is effective a deterministic ''shading correction.'' ¿ American Geophysical Union 1991