SAR Plugin

[rgleason]

I did a search for "Creeping Path Multi SRU" and came upon this US Coast Guard Appendix to the IAMSAR https://www.dco.uscg.mil/Portals/9/C...0M16130.2F.pdf
which is basically for aircraft searches.

Down on page H-37 page H12 there is a diagram showing a "Vector Plot of basic surface drift velocties" above that there is a section on that.
On page H38 there is a diagram for Sweep width and a bunch of selection tables dependent on positition of the sun, speed correction, object or target size correction, EPIRB sweeps, etc.

These are similar to the considerations for vessels I think.

[Ops.Navig8r]

Thanks Mike, I'll give that a go.
Happy Spudding.

[Ops.Navig8r]

Hi RG,
Thanks for the link, I'm sure I have that DOC somewhere, we here of course use the Aust. S&R Manual but things like search width are pretty much common, of course advice form the OSC or flotilla leader of sea conditions and vis are usually sort as many searches are done at night there is not much documented about that so often we are done to 50M or best spotlight range as you probably now spotlight range can by severely reduced by sea mist a well.
I think you would agree by looking at these search widths the surface vessels have fairly small spaces. I think you have worked this S&R stuff can be like a tin of worms.
cheers
Steve.

[rgleason]

Steve wrote:

These searches except the (PS) are generally for smaller targets and for you guys on vessel planning then the most likely use would be MOB. I that case the Oil Rig would be a good choice especially if following the calculated route. After all if you have a MOB drifting north why would you use a pattern that sends you South? As I said before these patterns usually Drift with W&T.

You make the point that the SAR Plugin would most likely be used for more timely MOB cases, by ships closest, with formal SAR occurring later and in that case, the Oil Rig search is most likely to be used, and the Parallel Search (PS) would probably not be used. A search pattern that responds to the drift (wind & tide) is most appropriate, so the oil rig search is appropriate.

Thank you for providing a link to a USCG automated search and rescue calculator and to your PDF worksheets to record smaller patterns using Distance/Speed/Time tables. May we include these in the manual?

These tables use a set speed and time to create the search pattern, rather than waypoints. The result is that set and drift characteristics of the search boat are used (which may be somewhat different that a MOB), which given the complexity of actually measuring/calculating set and drift and then creating a route and waypoints that respond, is a simple and practical approach.

Perhaps SAR_pi should have a new Speed/Time/Heading mode which would record the path taken as a track, and perhaps interactively provide directions and time for each leg, which would automatically include drift from Wind and Tide?

Steve, I can understand how the Oil Rig search would work in this way, but with the Sector Search aren't you always going back to the middle waypoint? ...or is it just done with the Speed/Time/Heading and if the actual track is looked at the sector search is distorted automatically by drift?

I recall a mayday with a lost diver last summer. There were 3 boats searching for him. He had been lost for 1/2 hour in an area where there were currents of 3-4 knots. The vicinity position was broadcast, I do not know what search pattern was used. Fortunately an hour later a motorboat found the diver on the beach. He and his buddy had gotten separated while down and he could not find the boat. My impression was that communications were difficult and the search was disorganized despite the 3 boats being active, due to training.

[Ops.Navig8r]

Hi RG,
I wrote in an earlier post that we create waypoints for VS, SS, and Oil Rig only to be able to plot them on an electronic chart. Son even the VS can be done "On the Drift" I said a marker with similar drift characteristics to the target ( ialso said that would be different for MOB as opposed to a boat and each type of boat) can be used to mark the center of the pattern and each time the SRU returns to where the marker was it corrects to the markers new position and then proceeds on the original heading there by correcting the "Datum" point for drift each time it passes the centre. As fa as trying to set up a calc for leeway ad set within the plugin, I think will be very difficult a you would need the time of the incident(which is often not known) the current speed and direction for the location on the day, the wind speed a direction and the drift characteristics of the target. The Police here have a professionally written program to predict a targets position after some hours once all the relevant info is entered, it was very expensive and at the end a calculated guess. We had a fishing boat lost overnight and the prediction area for the next day was over 300 Sq.Nm. the vessel was located right on the outer edge of the predicted area and you would think it would have been in the center somewhere. There is no way surface craft can search 300 Sq.Nm.
This is a link to look at the W&P leg calculator USCG use:
Course & Leg Identifier for Search & Rescue
You will see it too has distance/speed/time tables.
Before I seen the W&P device I made my own by plastic coating a printed document with adjustable disk, and some of our navigators carry those but I think those forms I set you are just as good.
When it come to finding your diver, you don't know if his on the bottom, drifting on the surface or a good swimmer with fins who can make some good ground well away from your search area, that can be tough and this is where you either need aerial help and or more than one surface search perhaps with different pattern types.
Cheers
Steve

[rgleason]

1. " I said a marker with similar drift characteristics to the target..." Yes you did.

2. "As far as trying to set up a calc for leeway ad set within the plugin,..." Agreed.


The link to Weems and Plath is very helpful, and David Burch's little utube demo explains the manual calc of of course and time, then he demo's use of OpenCPN to plot the search patterns and suggests use of the Route Manager to find the "time" for each leg. So to further refine this plugin, I think the "Time" and course for each leg should be made available somehow in an easy sequential way. (Perhaps I am over thinking this?)

[Ops.Navig8r]

Hi Rob, Maybe you is, I wrote to Mike in an email that at the end of the day mostly the people using OpenCPN for S&R are armature rescuers trying to do the right thing but eventually if a result is not forthcoming the pros will take over. I don't think it worth getting that complex average guy doesn't know what to do with it. I think you need you settle on a reasonable compromise, get the terminology right, I reckon your calcs are good enough after all if you had a space of 5 cables and the waypoint was even 20 metres out and it isn't it would not make any difference from a practical point of view, I would challenge the best to steer within 20 m of a route. even the best auto-helms have to correct and adjust for sea changes etc.etc. If you searching at 5 cables then you need to see at least 2.5 so at 463 m visual range 5-10m is nothing you could not tell if a boat was 470 or 450 m away.
The Weems & Plath is easy to use and you note in the PDF I sent you the tables are similar the main thing I think you will see the leg lengths are much shorter than 10nm and so I think they could be restricted on the plugin too.
Cheers
steve.

[rgleason]

Originally Posted by Ops.Navig8r

..so I think they could be restricted on the plugin too.

Steve, its Rick.

1. What do you think that restriction should be?
2. To set and calculate a search and then go to Route Manager and write down the times and course for each leg is sort of circuitous.

- I assume the route manager will use the speed set in the GPX? Have not checked this.

- I wonder if the display of the route will show course and time if the cursor is hovered over the leg?
- Then just let the drift occur as it does, and turn on tracking to record the actual track the boat is taking, and follow the time and course in the route.

I wonder if this would work?
I think we need some more detailed "beginning" instructions in the manual for this kind of MOB / Vessel search.

Variables to set:
Speed range: say 3-12 knots
Height above water: 3'-12'
Weather: clear, partial, fog 1nm, dense
Sea state: 1'- 5'
= Track width

[Rasbats]

Originally Posted by rgleason

Steve, its Rick.

- I assume the route manager will use the speed set in the GPX? Have not checked this.

Route manager does not use the GPX speed for import, only included in the GPX exported. I have raised a feature request for this.

Mike

[rgleason]

I suppose this just requires augmenting the GPX import to utilize the speed in the gpx.
Does Route Manager database need to be expanded to utilize unique speeds for each leg?
Is there any need for adding something in the API for speed? (I don't believe this is needed, but am unsure.)

[Gilletarom]

Rick,

Yes, I am sure, even without participating in the development of the API, that things must be added in the API so that OpenCPN is able to make the most of the speed registered in each segment of the route.

In version 5.0, this does not work.

I had the opportunity to write, several times, to Dave, and to Sean, that it was necessary to improve the route manager on this subject. And this is absolutely necessary to make another plugin, Weather-Routing, really usable.

Alas, this has always remained a "dead letter".

If the work on SAR could help us get Dave involved in route manager transformations ... that would be great.

[Rasbats]

Not each segment of the route, but the plugin can easily insert the plannd speed for each route in the GPX. No change is needed for the API, it is the main code base for route manager that needs a tweak.

Mike

[Gilletarom]

Originally Posted by Rasbats

Not each segment of the route, but the plugin can easily insert the plannd speed for each route in the GPX. No change is needed for the API, it is the main code base for route manager that needs a tweak.
Mike

It is true that, for a SAR-Route, the cruising speed is stable and identical on all legs.

[Moo]

Originally Posted by Ops.Navig8r

I would challenge the best to steer within 20 m of a route. even the best auto-helms have to correct and adjust for sea changes etc.etc.
steve.

I have driven hydrographic survey where we keep within 2m on our survey lines manually. An autopilot can't do that.

The secret to this a special display that is basically a highly amplified crosstrack that shows how far off the line you are and the present direction (away from or towards the line). As helmsman you keep an eye on this and steer to the instrument. It takes a few hours to master but once you have it is easy even with some sea running.

The biggest problem was maintaining the speed that the surveyor requested.

[Ops.Navig8r]

hello gentlemen,
I'm not sure which of these threads I should answer first. So Rick in an earlier response to Leg lengths I mentioned I have a drop down choice of only the distances used on my worksheets (Like the Weems & Plath Leg Identifier) so the speeds chosen align with the table on the W&P or my worksheet to get the time, this could easily be done in the plugin too and as it calculates the dis(VS) Sector search all legs are the same time, easy, the (PS) all parallel legs are the same but normally this is not done on the drift so time/speed calc is not so important but could still be done, the (SS) Expanding square would need more space to display the time and may then leg length with it as each is different, it this case you might stick to the rout/waypoint manager to get your info.
as surface craft the overall leg length for VS & SS are dependant on visibility Port/Starbord, the PS the length can be what ever but the "Space" between legs is determined by the vis. (Cheeky----I calculate all this in my software so the planners know now long to expect vessels do complete a task while planning the next, in this case I check Ocpn to see if its right LOL)

Moo, You are right about steering and I said similar, for all our Multi Vessel parallel creeping path searches (Not included the plugin) the yare always in a cardinal direction and the space between vessels (up to20) is given in Points of a minute Lat or long and each skipper steers to that minute so Xtrack is constantly corrected, as you said its not easily to say on course in some conditions and people don't go missing in millpond conditions. Our coxswains practice this continually. we conduct at least 4 exercises per year at nigh and 2 in daylight, the Police conduct one of their own planning with us once per year. I zoom in on the tracks and if vessels deviate more than 20m Big Brother is on the radio to see why, If we are searching at night for a person or body with a space of 50m then vessels can not deviate 20m each and risk collision or missing the target. Constant vigilance by cox and crew is required and to search at the same time.

cheers
Steve.