The geometric distortions attendant to spin-scan imaging were extraordinarily manifest in the Pioneer encounter with Saturn. By overlapping graphical predictions of these distortions with raster scans of the raw intensity data, both displayed to the same scale on a Versatec printer-plotter, we are able to determine the precise geometry of a data-taking sequence. The predictions are quite sensitive to the assumed dimensions of Saturn and its rings. We accordingly conclude that the ratio of polar to equatorial radius is 0.91 and that the Encke gap is 133,500 km from Saturn's center.