Rendezvous with moving target

[orangeherald]

Hi there,
I was wondering if you could please point me in the right direction.

I'm hoping to find out what the best way is to get OpenCPN to calculate the the course I need to steer in order to rendezvous with a moving AIS target?

Thank you!

[skipmac]

Does OpenCPN AIS calculate a CPA? If so a quick and dirty method would be to steer towards an estimated rendezvous point, look at the CPA and adjust your course to reduce the distance of the CPA.

[rgleason]

Yes Opencpn does calculate a CPA.

Originally Posted by skipmac

Does OpenCPN AIS calculate a CPA? If so a quick and dirty method would be to steer towards an estimated rendezvous point, look at the CPA and adjust your course to reduce the distance of the CPA.

[requiem]

A crude method, if you have course vectors displayed, is to simply adjust course until the Nth minute tick on your own course touches the same Nth minute tick on the other vessel's course.

If you are more interested in the actual end course, rather than specifically having OpenCPN do it, there is another way:

One thing I took from the "This Is Why People Get It Wrong" thread is that people might not be familiar with relative motion diagrams. I tried to put together some slides to help explain the basics, because if you understand them you can use them to quickly construct an intercept course. (Instead of finding a course with a safe CPA, you simply find one with a very unsafe CPA.)

Here's a link: https://docs.google.com/presentation...it?usp=sharing

(It should still be considered a draft, but since I was thinking of posting it for feedback soon I'll put it here anyway.)

[rgleason]

requiem, this is good. Can we link to it in the Opencpn Wiki, when you have it the way you want it?

[S/V Illusion]

We learned how to use a plotting chart in the CG.

[Canne]

See also: The Radar Navigation and Maneuvering Board Manual (Pub. 1310) Chapter 3 Collision Avoidance https://msi.nga.mil/Publications/RNMB

[rgleason]

This slideshow has some useful concepts:
https://docs.google.com/presentation...56039d35_0_194


CPA - Closest Point of Approach
TCPA - Time to Closest Point of Approach
BCR - Bow Crossing Range <--Just how far in front of you the ship will pass.

Two additional AIS features that would be very useful in the Target Query menu:

BCR -Bow Crossing Range Value added to Target Query menu and Rollover.
Vector Time Ticks (adjustable, 12 minutes) - Add adjustable time tickmarks option to AIS Toolbar Tab



See slide 32, Electronic Example shows

The course vectors are set to 12 minutes long. Each tick represents 1 minute of travel distance. Course vectors cross all the time. What to watch out for is when the crossing is at similar time, eg if tow cross at the 7 minute tick for each..

[rgleason]

Added to AIS wiki Resources: Rendezvous with moving target