A system for proximity sensing on a marine vessel includes a main inertial measurement unit (IMU) positioned at a main installation attitude and a main location, a first proximity sensor configured to measure proximity of objects from a first sensor location, and a first sensor IMU positioned at the first sensor location and at a first installation attitude. A sensor processor is configured to receive main IMU data from the main IMU and first IMU data from the first sensor IMU, and then determine a relative orientation transform between the main installation attitude and the first installation attitude by comparing the main IMU data and the first IMU data, and then determine a relative position transform between the main location and the first sensor location based on the relative orientation transform, the main IMU data, and the first IMU data.