In conjunction with the standard RYA Radar training Allabroad go one stage further with full Marpa training with simulators. Marpa is a great tool but in order to fully understand Marpa we teach manual old school Radar plotting first and then apply that knowledge to our Marpa training sesions. Marpa can be a great tool in thick fog and at night in busy areas where there is more than one target in view at any one time. The Allabroad simulation suite allows you to practice without the risk!
MARPA in more detail...
User selected Targets are initially highlighted on the display with a small box whilst MARPA resolves the relative motion by comparing the relative motion of the target on the screen with the true, actual motion (speed and heading) of the tracking vessel. Once resolved the acquiring box will become either a Circle for safe targets or a triangle for dangerous targets. MARPA can indicate further information with 2 very different but similar looking vectors: True Vectors and Relative Vectors.
True heading and speed of a target can be ascertained with a True Vector, the length of the line indicates the distance the target will actually cover per duration of vector, usually 6 or 3 minutes (this is user selectable) although, range permitting, the 6 minute vectors provide quicker mental calculation of speed. Eg True 6min vector (TV6) of 0.75 NM indicates the target's true speed is 7.5 Knots, the direction of this vector indicates the vessels heading relative to the tracking vessel or its electronically fed heading if one exists.
The relative motion of a target can be seen with Relative vectors, these just show the future position of the target on the Radar screen as per Vector Duration, again usually 6 or 3 minutes depending on range in use. A relative vector of 6 minutes (RV6) would be a line representing the movement of the target for the next 6 minutes. Most colour Radar displays can show both TV and RV simultaneously. It is essential that users of MARPA do not confuse RV and TV, especially on Radars that can not display both. True vectors allow users to, at a glance, determine the aspect of a target, something that is virtually impossible to do without manually plotting, Relative vectors provide users with, at a glance, information about which vessels pose a collision risk, a RV pointing at the centre of the Radar screen indicates there is a risk of collision.
All the information pertaining to a target is also available numerically however when tracking multiple targets this information distracts the user from the image, and with proper training, viewing vectors is much safer.
Allabroad Sailing Academy
MCA STCW95 Yachtmaster Training Facility
7 The Square
for course Advice
Tel: 00350 200 50202
Tel UK: 0044 7872 223325