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Old 07-03-2014, 06:27   #1
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CPA / TCPA calculation to any point on map

Hi everyone,

I've been using openCPN for a few weeks now and I'm delighted with all the possibilities we get for free.

However, there is one little option I'd like to use, but it seems like I can't get it to work.

What I'd like to achieve is to get a CPA/TCPA for an AIS target, but not relative to my boat position but relative to the port entry.

I'd like to know in wich order and at what time boats will enter the port.

I tried to deactivate my GPS and manually position my boat, but when I do so, CPA/TCPA aren't available anymore.

Does anyone here know if it's possible to do such calculations?

Thanks in advance for any help!

Cheers,
Erwin
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Old 07-03-2014, 10:44   #2
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Location: Orust Sweden
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Re: CPA / TCPA calculation to any point on map

Erwin..
I don't have a solution for your real request but I can share my way to solve a similar situation.
Normally I have the course arrows for the AIS target and my own boat set to 30 minutes. It use to be sufficient to be able to predict the future locations and where we will meet. But if you have one hour to the port you can change the arrows to that value instead.
The arrows are set in Tools-Ship-AIS_ship. (All commands directly translatadet from my Swedish version. Please try to transmit to your language.)
Håkan
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Old 07-03-2014, 11:25   #3
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Re: CPA / TCPA calculation to any point on map

Hi Hakan and thanks for your answer.

Your solution does work and I sometimes use this option to predict ETA of a particular ship.

However, the port entrance can sometime be filled with lots of ships and as a boatman association (responsible for ships mooring), I have to predict in which order boats will arrive so that I can send the right team to the right boat in the right order and at the right time.

Do you (or anyone else) know why CPA/TCPA is deactivated when you manually place your ship on the map? (If it wasn't disabled, I could simply place my virtual ship between both dikes.

Cheers,
Erwin

PS : Thanks again Hakan for trying to help me, and btw my main language is french.
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Old 07-03-2014, 12:48   #4
bcn
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Re: CPA / TCPA calculation to any point on map

The solution would be a (virtual) RMC sentence send with the fixed position you need as the reference. And not having any other GPS source connected.
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Old 07-03-2014, 15:24   #5
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Re: CPA / TCPA calculation to any point on map

Quote:
Originally Posted by bcn View Post
The solution would be a (virtual) RMC sentence send with the fixed position you need as the reference. And not having any other GPS source connected.
That's a nice idea. Do you know how I can do such a thing?

I guess that even with this nice workaround, I would be stuck with one virtual position, and won't be able to get TCPA for differents points ? (other dikes for other port entry and/or actual ship destination inside the port)
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Old 08-03-2014, 01:47   #6
bcn
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Re: CPA / TCPA calculation to any point on map

Quote:
Originally Posted by 3rw1n View Post
That's a nice idea. Do you know how I can do such a thing?

I guess that even with this nice workaround, I would be stuck with one virtual position, and won't be able to get TCPA for differents points ? (other dikes for other port entry and/or actual ship destination inside the port)
Might be programmed as an option in the contextual menu:
..
- Move Boat Here (which only exists if no GPS active)
- NEW Send Virtual Position From Here --> $VPRMC
.....

You can put this in Flyspray as a request if you like.
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Old 08-03-2014, 01:52   #7
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Re: CPA / TCPA calculation to any point on map

Quote:
Originally Posted by bcn View Post
Might be programmed as an option in the contextual menu:
..
- drop boat here (which only exists if no GPS active)
- NEW send Virtual Position from here --> $VPRMC
.....
That seems perfect!

But... how can I program such a function?
I know how to use javascript and/or php quite well, but how would this be programmed in openCPN ?

Quote:
Originally Posted by bcn View Post
You can put this in Flyspray as a request if you like.
I'll check what Flyspray is right now.

Thanks a lot for your time and knowledge! :-)
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Old 08-03-2014, 01:55   #8
bcn
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Re: CPA / TCPA calculation to any point on map

Flyspray is our bug tracker at OpenCPN.org.
You will have to register in order to enter request or bug reports.

So if a developer is interested to implement he will do so.
Or you learn C++
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