On the
radar target
tracking:
There are three ways you can track targets with the
OpenCPN radar plugin:
1. On the radar chart overlay click the right mouse button on or close to a stable radar return. The target will be selected by the MARPA system, possibly locked and tracked. Target information (position, speed and heading) will be send to
OpenCPN and handled there as if it were an
AIS target. In case there is a real
AIS target close to the same location, the radar target will not be displayed separately.
2. Set a guard zone and activate ARPA on that zone. The guard zone can be a circle limited by an inner and an outer range or a a segment of this circle, an
arc. Activate the ARPA function on the zone selected. All radar returns inside the zone will be processed by the ARPA system. That means that if the return is stable it will be locked and tracked. Further handling as under 1. Land masses often give unstable returns and these return may be above the size of a regular target. Such landmasses may confuse the ARPA system. Better is to configure the guard zone in such a way that land is not included.
Above two methods are available for all supported radar types. For the
Navico Halo Doppler radars the beta 3 release adds a new way of getting radar returns tracked.
3. For Halo Doppler radars only. Click the View menu. Try the Doppler button. When you set this on "approaching" all radar returns that are getting nearer to you will show in yellow. These are approaching Doppler targets. Now click the button below the Doppler button, the DopplerAutoTrack button. Put this "On". Now all yellow returns (approaching) will be tracked by the ARPA system and handled as described above. This third function can be used in combination with a guard zone. But if you want to get acquainted with it, or just want to test it, better switch the guard zones off, because you would not know how a target originates.
For the DopplerAutoTrack funcion it is not necessary to switch "Doppler approaching on" (mark targets yellow), as the system will recognize approaching targets anyway. But doing so, makes you image better readable. When a Doppler target is no longer approaching (it has passed), it will no longer be tracked and is marked as "lost target", it will soon disappear as a target but may still be visible as a radar return.
The essence of this new function is that you skip the "trouble" of setting a guard zone. And as only "yellow" (approaching) returns are considered, the discrimination is much better. You should only get targets you are interested in.
Douwe Fokkema