Parallel Indexing (PI) for Course Alteration_Radar Navigational Tutorial. This video explains how parallel indexing is used during course alteration to monitor a vessel's position along the planned track. Using radar tools such as EBL and VRM, the Officer of the watch can quickly detect any deviation from the track and take immediate corrective actions. #parallelindexing #passageplanning #navigationalAid #arpa #marineradar #NauticalAcademy