Abstractthe problem of defining the relative and geographic coordinates of an acoustic sea‐floor transponder array is examined. Effects of refraction to slant ranges of 10 km are shown to be compensated for by the use of a harmonic mean sound speed. Ranges measured with an acoustic transponder are compared to those measured by a tellurometer. Methods of Cloverleaf measurement of acoustic transponder depth, Baseline Crossing measurement of transponder spacings, and an iterative technique for determination of array coordinates are described. All three methods are used to determine the configuration of a transponder triad in deep water near Antigua. The most efficient method of establishing relative and geographic coordinates of an array of sea‐floor acoustic markers is identified and discus