Do we need/want an AIS filter?

[Hakan]

Dirk
Thanks, I pulled your Git and now it builds fine also in W.
I've to read back to see what the filter is about. Sorry I haven't followed this but so far I saw "Non important" targets are smaller and without target names.
Håkan

[rgleason]

Hakan aren't you good. I decided today I needex to build it and you beat me. More later. Thanks.

[Hakan]

Dirk or anyone..
This works very good and if understand it correct the filter scale targets size and some properties, like ships name, according to weighted rules.
Would you mind describe the filter logic and the impact of the different scale values given in the config file so I better understand how it works. I could of course read the code but I'm booth a little lazy and not so skilled I easily can get a good logic picture.
IOW - A logic description or a diagram would be very appreciated.

Many thanks/
Håkan

Rick.. Hope you don't mind I unintentionally run over you. (I also hope this was English and not to much Swinglish?)

[rooiedirk]

Håkan
I'll give it a try.
The "importance" of a target is depending on:

• The Speed of the target, faster targets are more important. The max speed acknowledged is hard coded at 12 knots.
• The CPA the closer a target will come the more important it is.
• The TCPA if the time to 'collision' is small the target is more important.
• The Distance to the target, far a way is less important.
• The class of target. Class B targets are (little) less important.

For each point above a factor is calculated. The highest value of this factor is depending of the value in the config file. All these values are then added, wich gives each target a 'weight'.

From all targets the top [number] weights are displayed as important. Only a certain [number] of important targets are displayed, depending of the value in the options dialog.
The value off the added points needed to be 'important' is depending on the other targets (floating). As long as it in the top [number] it will be displayed.


The size of the scaled down target can be adjusted with the [AISScaledSizeMinimal=50] in the config file, where 50 stays for 50%


Scaled down targets don't have names , no nav status symbols, and no heading line.


Glad you like it, and hope this does help to understand it.
Dirk

[Hakan]

Dirk
Many thanks, most clarifying but some notes to check if I understood.

1] re: As long as it in the top [number] it will be displayed.
I assume you mean "...... it will be displayed in full scale" You never hide any targets, just scale down if of low importance?

2] re: ................ symbols, and no heading line.
But the SOG line is (fortunately) still there, what I can see?, see pic. (Is there ever a heading (HDT/HDM) line on a AIS target?)

3] Q - Scale down: The scale down or not scale down is a tripping point, on/off, and not a importance dependent stepped value down to the 50% - right?

Håkan

[rooiedirk]

Håkan
1. Yes correct I only scale down and never hide.
2. Strange, I thought the SOG vector was also hidden, Please let me now what you prefere.
3. Correct There are only two outcomes, normal or small. However the rolling over is going slowly. (goming up is going faster then going down.)
I did try with scaling depending on weighing factor but then the display was very unquiet, a bit like looking at a fireplace.
Dirk

[Hakan]

Dirk

2 - SOG line. Whatever happened I'm not sure of my own preferences. I do think I'd like to see the line but now it's very prominent over the tiny ship symbol. The SOG line ought to be scaled as well but of course we can't scale the length and not the thickness! What about making it transparent? Would that be a heavy coding exercise?

3 - OK, very nice - that's why I saw it in difference sizes.

Thanks
Håkan

[rgleason]

Dirk's First description:
http://www.cruisersforum.com/forums/...ml#post1973497

Second description when implemented:
http://www.cruisersforum.com/forums/...ml#post1977415

Final description to Hakan
http://www.cruisersforum.com/forums/...ml#post1979806

=====
Just a few edits / clarifications / consolidation:

TARGET SCALING
-------------------------
Description:

AIS Display Filter to reduce the size of unimportant targets, to be used in crowded areas where the screen can be too clogged to be useful. The filtered targets remain visible but are smaller and without AISname.

The "importance" of a target depends on:

• The Speed of the target, faster targets are more important. The max speed acknowledged is hard coded at 12 knots.
• The CPA the closer a target will come the more important it is.
• The TCPA if the time to 'collision' is small the target is more important.
• The Distance to the target, far a way is less important.
• The class of target. Class B targets are (little) less important.

For each point above a factor is calculated. The highest value of this factor depends on the value in the config file. All these values are then added, which gives each target a 'weight'.

From all targets the top [number] weights are displayed as important. Only a certain [number] of important targets are displayed, depending of the value in the options dialog.

The value of the added points needed to be 'important' depends on the other targets (floating). As long as it in the top [number] it will be displayed in full scale. All other targets are scaled down if of low importance.

The size of the scaled down target can be adjusted with the [AISScaledSizeMinimal=50] in the config file, where 50 stays for 50%
Scaling is on or off depending on the number of important targets set, scaling down is a set amount, with no gradation. There are only two outcomes, normal or small.

Under Options > Ship > AIS Tab > Display

[Checkbox] "If more than ...[#] targets, scale down the less important ones. [ 5 ]

Scaled down targets don't have names , no nav status symbols, and no heading line.

Hakan writes: But the SOG line is (fortunately) still there, what I can see?, see pic. (Is there ever a heading (HDT/HDM) line on a AIS target?)

Configuration File opencpn.ini
In the config file the weighing of each used value can be changed, although I believe the default values are not to bad.

AISScaledNumber=5
AISScaledNumberWeightSOG=150
AISScaledNumberWeightCPA=100
AISScaledNumberWeightTCPA=100
AISScaledNumberWeightRange=100
AISScaledNumberWeightClassB=-20
AISScaledSizeMinimal=50

[LeaseOnLife]

Hi Dirk

good work.

I would prefer to give SOG less weight, I guess it would depend on the surroundings.

Below is a screenshot how it would look in Singapore. See the small target, with a small SOG, crossing my virtual bow. This is probably a smaller ship, like a bunker barge, visually hidden behind a bigger ship. In congested waters like this, I would set the SOG weight smaller. I don't want to hide the anchored/not moving targets, but want to be alerted once one of them moves. Maybe a threshold for SOG to minimize non moving targets is needed?

For open water the default settings look OK.

LeaseOnLife (another Dirk)

[rgleason]

To correct earlier post:

USCG Rule change issued in January 2015.
US Coast Guard AIS Transponder Rules | Vesper Marine

Types of Vessel Requiring AISAIS Class Required

Commercial fishing vessels >= 65 feet Class B

Commercial self-propelled vessels >= 65 feet certified to carry < 150 passengers Class B *

Dredges operating outside shipping fairways Class B

Towing vessels >= 26 feet and > 600 hp Class A

Vessels moving certain dangerous cargo Class A

Other commercial self-propelled vessels of >= 65 feet not described above Class A

[rgleason]

Vesper 850
------------------

Target Prioritization - See the most important data! Set up so targets are prioritized by CPA and TCPA. See the first target on the list is the most dangerous.
Alarm / Filter Profiles - The 5 alarm and 4 filter settings are organized into four profiles: anchored, harbor, coastal and offshore. Easily customize each profile to your preferred settings.
Alarm settings - Optional mute for triggered alarms. Alarms for all other targets are stay active. Mute can be turned off and alarm for this target can be reactivated.

Panbo: The Marine Electronics Hub: Vesper Marine WatchMate, still the leader in AIS collision avoidance?

Profiles (4)
User can create profile settings for different conditions.
- Anchored
- Harbor
- Coastal
- Offshore

SETTINGS

Display orientation - north or head up

Filter -4 ways, but not ignore
- Target speed filter - Targets which have a speed > 10 knots will be shown
- Target range filter - Targets which have a range < 2nm will be shown
- Target CPA filter - Targets which have a CPA < 2nm will be shown
- Target TCPA filter - Targets which have a TCPA < 10 min will be shown
NOTE - Reduces screen clutter by dropping the visibility of targets. Ocpn does not do this. RooieDirk's Target Display Filter changes icon scale.

Alarms - 4 cpa alarm parameters
- Guard alarm range - circular guard range alarm
- CPA alarm - CPA alarm triggered if distance < 2 nm
- CPA alarm TCPA - CPA alarm triggered if time < 30 min
- CPA alarm Target Speed - CPA alarm triggered if moving => .2 knots.
- CPA alarm Your speed - CPA alarm trigger if your speed => X knots

[rgleason]

I think a separate revolving toolbar icon for AIS Profiles settings with
- Anchored
- Harbor
- Coastal
- Ocean
- AIS OFF
would work. It is another icon on the toolbar.

Dirk's Target Scaling would be set from within the profiles.

[rooiedirk]

@LeaseOnLife
Hoi Dirk,
Nice example of a busy area. Do you have a VDR file available for testing??
Dirk

[LeaseOnLife]

Originally Posted by rooiedirk

@LeaseOnLife
Hoi Dirk,
Nice example of a busy area. Do you have a VDR file available for testing??
Dirk

I do, but it is worldwide, with >20000 targets, and causes other issues, see
http://www.cruisersforum.com/forums/...ml#post1980056

https://drive.google.com/file/d/0B1c...ew?usp=sharing


(the other) Dirk

[rgleason]

Dirk's repository is https://github.com/RooieDirk/OpenCPN
The new Target Display Filter is under branch "AIS-filter"
so go to your git directory
git clone git://github.com/RooieDirk/OpenCPN OpenCPN-Target_Display_Filter
puts Dirk's Opencpn code in OpenCPN-Target_Display_Filter

Then
git checkout -b Target_Display_Filter --track origin/AIS-filter

makes and new local branch which tracks Dirk's origin/AIS-filter
Then you must add some necessary files and create the build directory.
from the build directory
cmake -T v120_xp ..
cmake --build . --config release
cpack

-------------------------------------------------------
This has been uploaded to
OpenCPN Beta File Thingie rguser rgpass
as
Opencpn 4.1.1108-Target-Scaling

You will need to install it to the Opencpn 4.1.1108 directory.

Try it out. It seems to be working well.