Navico radar plugin v2.0 released

[Hakan]

jimthom..
For your info is the beta version as of Douwe's link including code for ARPA targets. It's very good. I've tested the last beta today. Guard alarms works fine for me also here.
The guard and ARPA areas are handled by the same menu. You've have to select what option to use, or both.
You need to use OCPN version 4.5 or later.
My attached picture is in Swedish but i think you'll get it.
Håkan

[jimthom]

Thanks; I've downloaded 2.3 and this is what a possible guard zone could look like. It triggered an alarm. First success.

[jimthom]

yeah!

[Douwe Fokkema]

But when you use such a narrow band as guard zone a target might pass through between two radar sweeps and remain unnoticed.

[jimthom]

My math's must wrong. At 20 knots he would pass through the 1/4 NM zone in 45 seconds. If the radar is rotating at 24 RPM (once ever 2.5 seconds), he would be in the zone for 14 passes.

[JeroenAdam]

Thanks for the good work on this radar plugin. I'll be doing the strait of Gibraltar in two weeks (Rabat-Tanger-Smir) and make some screen captures. All set with v2.3 beta and OpenCPN 4.6.1


I saw some fixed code on Github 5 days ago, should I compile from Github (never done before, seems not that hard, I'm on W10) instead of using the dropbox download?

[Hakan]

JeroenAdam....
For once time just now there will be no difference.
To test future changes it's a good idea if you would like to try compiling and won't rely on others binaries services.
I suppose you've read the developer's wiki how to set it up.
Håkan

[Douwe Fokkema]

Regarding the ARPA and MARPA functionality in the new beta release of the Navico / Lowrance radar plugin some further explanation may be useful.
ARPA stands for Automatic Radar Plotting Aid, MARPA for Mini (or Manual) Automatic Radar Plotting Aid. These functions turn returns on the radar screen (blobs) into objects with a position, heading and speed. These objects are in our case passed to OpenCPN that handles them as AIS targets.
Let's first look at MARPA, the manual function. When you click the right mouse button close to a radar target (blob) that you want to follow, and then click “Set ARPA target” the blob will get a white contour around it as a sign that the acquisition has started. After that a dot (a small colored circle) will appear on the target. Initially this dot is yellow, meaning that the target is in the acquisition stage. When it turns green, the target is locked, the software has acquired the necessary parameters and will hold on to the target. Here we actually use similar algorithms as are used in defense systems to track incoming missiles. The target data is passed to OpenCPN that will further handle it as an AIS target. If the radar misses the target during a sweep, it will change color to yellow. If it is missed during three consecutive sweeps, it is considered lost and will be removed from the display.
In OpenCPN, tools menu, under Ships, AIS targets you can set the conditions for the target to raise an alarm. So you can set the minimum CPA (Closest Point of Approach) and the time to reach the CPA. And you can let a sound play when the alarm conditions are satisfied. When a target is considered “dangerous” (satisfying the alarm conditions), it is colored red on the display.


To delete an ARPA target, click the right mouse button close to (but not on) the target and press “Delete ARPA target”. To delete all ARPA targets, click “Delete all ARPA targets”.


ARPA, the automatic function, works from the guard menu. So when you have defined a guard zone, click ARPA on for that zone. Now every target that appears inside this zone will be turned into an ARPA target. But only if it can be followed individually. Waves that generate radar returns will normally not be detected (unless they are there all the time). When a ship enters the zone, it will be turned into an AIS like target, with a speed and a heading. OpenCPN will then generate an alarm if the ship is considered dangerous. But you have to set the conditions for the alarm first in OpenCPN as described above. So you will no longer get an alarm for every blob in the guard zone, but only an alarm for dangerous objects. And you don't see blobs around you, but vessels with speed and heading. Avoid land masses inside the zone, due to the random returns, they might generate many random targets. The system is designed to handle over 100 targets reliably.

[bcn]

Douwe,

what happens when a target is already an AIS target, using an AIS transponder?

Hubert

[Douwe Fokkema]

When an ARPA target is at the same lacation as an AIS target (within certain limits) we suppress the ARPA target and don't pass it to OpenCPN.

[jimthom]

Hello Douwe;
I've been planning my radar installation for the last six months with the wish that you would reach this stage of development with your plug-in in a timely manner to catch the trade winds through S.E Asia. I'm a 75 year old singlehanded sailor who's started building his boat 17 years ago and has been sailing for 2 years, with the hope of sailing back to US from Australia to see my family.
Without your plug-in, please believe me, I would not even contemplate such a journey.
So congratulations on what you have achieved and all the best.
Cheers, Jim

[Douwe Fokkema]

For further explanation of the use of ARPA, I attach a screen image that I took today.
You see a guard zone that protects my forward view. In the guard dialog I have checked "ARPA" and not "Alarm". I you would use "Alarm", the guard zone would be useless, giving a continues alarm because there are many returns inside the zone. On my port bow you see two AIS targets, that did not cause ARPA targets. The other targets are ARPA targets automatically created by by the guard system as they were detected inside the zone. ARPA83 has left the zone but continues to be tracked. If you would put the mouse pointer on it in OpenCPN, you get it's heading and speed. ARPA106 is a buoy, a stationary target. In this zone no alarms are raised as none of the targets has a CPA (Closest Point of Approach) of less than 0.2 mile, the limit I have set in OpenCPN. The tracks you see behind the targets are done by OpenCPN, switched on on the tools/ships/AIS page.
In the picture there is also a landmass entering the guard zone. Normally you should avoid this, the landmass give rise to targets that make little sense. But in this case they don't really harm.

Good sailing!
Douwe Fokkema

[petter5]

Just curious, I see from the screen shoot that you use a very old version of opencpn. Any specific reason for that ??

Originally Posted by Douwe Fokkema

For further explanation of the use of ARPA, I attach a screen image that I took today.
You see a guard zone that protects my forward view. In the guard dialog I have checked "ARPA" and not "Alarm". I you would use "Alarm", the guard zone would be useless, giving a continues alarm because there are many returns inside the zone. On my port bow you see two AIS targets, that did not cause ARPA targets. The other targets are ARPA targets automatically created by by the guard system as they were detected inside the zone. ARPA83 has left the zone but continues to be tracked. If you would put the mouse pointer on it in OpenCPN, you get it's heading and speed. ARPA106 is a buoy, a stationary target. In this zone no alarms are raised as none of the targets has a CPA (Closest Point of Approach) of less than 0.2 mile, the limit I have set in OpenCPN. The tracks you see behind the targets are done by OpenCPN, switched on on the tools/ships/AIS page.
In the picture there is also a landmass entering the guard zone. Normally you should avoid this, the landmass give rise to targets that make little sense. But in this case they don't really harm.

Good sailing!
Douwe Fokkema

[Douwe Fokkema]

Originally Posted by petter5

Just curious, I see from the screen shoot that you use a very old version of opencpn. Any specific reason for that ??

No it is a very recent beta version in which the version number has not been set. I compiled it myself to try out some updates.
The br24radar_pi requires version 4.6 of OpenCPN or later.

[rgleason]

Douwe and Hakan,

Are there any updates/edits needed to keep your great documentation current in the Marpa/Arpa and perhaps other areas?

https://opencpn.org/wiki/dokuwiki/do...ais:br24_radar