PPI -- Plan Position Indicator. The sweep is a radius on the tube face (from the center to the rim of the tube), and the sweep moves around through 360 degrees. This type of presentation gives the azimuth of the target by the direction of the radial line, and range by the distance of the target's signal from the center point of the tube. Image of PPI Scope showing land and signals made by ships. Image of PPI Scope showing land and signals made by ships.