Also if your boat is moving backwards the unit (GPS) does not know this. It assumes that the boat is always moving/pointing forwards so anything marked in the right Si beam would be physically to the right of the boat and transducer. When you are moving backwards the unit believes that the boat is pointed in the opposite direction so anything marked in the right Si sonar is physically to the right of the boat/transducer but the unit will actually mark it to the left of the boat since it believes that the transducer is pointed in the direction the boat is moving.