Dead Reckoning Plugin for OCPN

[sinbad7]

In the meantime I am using the OCPN ´Create Route´facility to draw the two cross bearings
I have taken with my hand-held bearing compass I always have on board.
Remember to use the ´Reverse Route´facility when you click on each bearing line.
You can now use the two attached calculation utilities for course,distance and speed as well as for the calculation of the lat/lon of your next waypoint.

You can of course also take a running bearing 45° of an object and measure the distance sailed on the log when you have the object 90° abeam. This will be the distance you are clearing the object.

If you also keep an eye on the soundings near your´triangle of error´ it might give further reassurance.

The old salts know this already but there will be some who do not!

Tore

[Dutcho]

Hi Zoef,

Of course when the power supplie or computer is broken you go to your next plan. The paper chart. But as long as I can prevent that and use the ease of a computer I will. If needs be for a big ocean passage you create your own "washing chart" for the DR plotting and celestial observations.

Regards, Martijn

[sinbad7]

In addition to the facilities for DR set out in my #31 you will of course also use
OpenCPN´s Route Properties where you can enter the start time and speed in order
to view all the listed WP predictions. Inserting new WP´s en route automatically
calculates ETA as well as lat/lon.

All the ingredients are there but we need a way to automate it.

Tore

[sinbad7]

As a safety backup to our electronic nav system, GPS Essentials also have an additional bearing compass smartly built into the camera viewer with a central target finder,quite ingenious really. You can even take a photo of the bearings.

Would be a good supplement to the planned DR plugin for OpenCPN.

Tore

[sinbad7]

Keith..

In case you have shelved your planned DR program/module,have a read at this thread which looks very interesting.

http://www.cruisersforum.com/forums/...tml#post987954

Tore

[rgleason]

Thanks for your efforts in this direction. I think DR backup utilities would be useful.

[sinbad7]

The requirement and the wish-list is there,what we lack is someone with programing skills who feels it´s worth his efforts.

Tore

[RobertLeask]

Hope I'm not posting this in the wrong thread, but I haven't found one that covers the topic I'm interested in, this seems like the closest to it. If it doesn't belong here, maybe I should start a new one.

What I'm looking for is an electronic charting/navigation system that will let me display my dr vector on the chart, using heading and speed through the water, as well as the course made good from gps. From those two vectors the set and drift is simply the third vector from the dr to the fix. Traditionally the dr line was indicated by a single arrowhead, the cmg with a double, and set/drift with a triple. The only one I've found so far that can do it is Transas NaviSailor, but the price is in the thousands, a wee bit out of my budget.
All I want is to be able to see that on my chart, to be able to switch the dr vector on or off. It would be great to display the set/drift vector if I want, and I'm not sure if even the high end NaviSailor will do that. It seems to me a rather modest thing to ask for, but talking with a great many electronics salesmen I have come to the conclusion that electronic navaids have caused the near total extinction of the art of navigation. Forgive me if I'm wrong, but it looks that way.
In NaviSailor you can switch on both vectors and they are displayed just the way an old fashioned navigator would have drawn them on his chart, the set and drift is the bearing and distance between the two, and can be read out from an information window. I don't know if it can be graphically displayed on the chart. What I think is really brilliant about NaviSailor is that if you hit Man Overboard, it will predict where the person will be using the real time drift rate at the point it was triggered. And best of all, it doesn't have the silly boat icon that points in the direction of your cmg. That is something I can't get used to and I would very much like to never see again.
My first question is: can it be done in Open Cpn, by loading the dr plugin? Second: does this belong in another thread, or a new one?

[rgleason]

DR Wish List - requested
----------------------------
1. Display DR vector on the chart, (HDG and STW), as well as CMG vector, the Fix (course made good from gps).
2. Display Set & Drift Vector derived from the two vectors above, simply the third vector from the DR to the Fix.
3. Traditionally
-DR line was indicated by a single arrowhead,
-CMG with a double arrowhead
- Set/drift with a triple arrowhead.
4. Information -bearing and distance of the vectors
5. Control
-DR vector on and off
-CMG vector on and off
-Set/drift vector on and off
6. Vectors should be shown with tick marks for each knot, with user adjustments for length and units.
7. NaviSailor - if you hit Man Overboard, it will predict where the person will be using the real time drift rate at the point it was triggered.

-------------

There are two new Plugins that might be useful. It might be good to determine which plugin could be enhanced for the above wishlist, so that a feature request could be entered into Tracker.

ODraw Look under EBL

DR Route

Also there is work being done in TackandLay and Dashboard that may be applicable.

[jongough]

Rick,
How do you want to obtain the HDG & STW? HDG is available if an auto pilot is connected or a heading sensor and STW may be available if a speed transducer is connected, but if either or both of these are not available what should be done? The OD DR function only uses the GPS information to pre fill the DR create information. It would not be too difficult to add the other vectors and then create some based on calculations.

Is this a requirement for vector lines connected to the boat and showing real time changes, i.e. if the heading changes do the lines need to be recalculated? What is going to happen with this information?

All plugins can get all NMEA messages, but as has been discussed else where the current messaging process is rather heavy handed and is synchronous in nature, so this will add to the load. If the requirement is to have the display updated once a second or less, then this could be done via a timer whilst the information is gathered from the JSON messages.

If this is to be done in OD I think it may have to be for OD 1.4 rather than the up coming OD 1.2. What do you think?

Regards
Jon

[rgleason]

Dear Jon,
I had some preconceived ideas from before you started ODraw for a dynamic plugin that would show the vectors for forces acting on a sailboat, say every 5-10 seconds. Such that it would show these Vector Forces.
-Heading & STW
-COG & SOG
-Leeway Speed & Direction
-Current Speed & Direction
-True Wind Speed & Direction
-Apparent Wind Speed & Direction
- What have I forgotten in this list?

As ODraw developed I saw an opportunity to implement this and made some tracker entries accordingly and also transferred some earlier tracker entries to ODraw just as a placeholder.

Some of these functions/features are partially present in Dashboard, ODraw and Tactics_pi. In fact, tactics_pi has lead the charge in the direction of providing much of this information digitally, however it is not in a more visual vector format. Although Thomas has done an admirable and difficult job filtering and working out all the calculations, linked to recorded performance data in the form of Polar files, Target Boat Speed, Target %, VMG etc. I would still like to see a visual, dynamic vector based representation of the nmea data available, perhaps an averaged one, that takes in 5 minutes of data and then displays it, with options for turning on and off the various vectors. Somehow I think this might be helpful for sailing optimally,(whiich is the goal of tactics_pi) but having not seen it working ever, it is hard to know.

Interestingly, this vector concept is also at the basis of Dead Reconing, which is a hands on vector based method for figuring out where to head when there are other forces at work. I think expanding on these kinds of DR Tools would be the next step for ODraw.

I would love to see an ODraw object for planning that would allow user DR input for each of these vectors with the graphical vectors changing accordingly. I think it would be a useful planning tool that is at the heart of a question powerboaters and sailboats need to answer.

The diagram is direct from Thomas Rauch's Tactics_pi pdf. Creating this ODraw Object is in a direct line from the ODraw EBL Object that has developed so nicely. I guess the first step would be to turn the EBL into a Vector (direction & speed), then use that to create this more complicated object. At some point after this is working, it could be connected to available nmea data averaged over some user set 2-10 minutes. Of course the diagram below could first be simplified by just doing Drift (current+leeway) and the
HDT+STW vector
COG+SOG vector,
Drift vector (current + leeway)




PS: I would like to encourage RobertLeask to review and advise about the graphical standards for DR representations and notation, so that the DR functions are close to or equivalent to standard procedures, if that is possible Jon?

[rgleason]

I think I need to give Thomas a huge thank you here, and to say that Tactics_pi has all the elements of the earlier idea for Vector representation of forces, except it is currently not showing as a graphical Vector representation (direction + speed) centered around the boat position. Additionally, I need to add that I am not an authority on how to properly present complex data and of course Tactics_pi is new and will change and improve, based on user input and Thomas's interest.

In fact, tactics_pi has lead the charge in the direction of providing much of this information digitally, however it is not in a more visual vector format. Although Thomas has done an admirable and difficult job filtering and working out all the calculations, linked to recorded performance data in the form of Polar files, Target Boat Speed, Target %, VMG etc. I would still like to see a visual, dynamic vector based representation of the nmea data available, perhaps an averaged one, that takes in 5 minutes of data and then displays it, with options for turning on and off the various vectors. Somehow I think this might be helpful for sailing optimally,(whiich is the goal of tactics_pi) but having not seen it working ever, it is hard to know.

===
To answer:

How do you want to obtain the HDG & STW? HDG is available if an auto pilot is connected or a heading sensor and STW may be available if a speed transducer is connected, but if either or both of these are not available what should be done?

-It's would be entered by hand under properties, or graphically by drawing, no connection to nmea data for now. If this info is not available, just the COG+SOG vector is drawn and the other two are not. If you know or want to assume the Drift vector, you can enter that and the 3 vectors will resolve. Etc

[rgleason]

If this Fix/CMG - Drift - HDG/STW Vector object gets working (what could we call it?), then it would be relatively easy to adapt it for other triangulation problems too, I think

[jongough]

Hi,
I've been thinking about this. Should there be a separation of work? i.e. OD does the drawing on the screen based on information that the Tacticks plugin can provide. This would mean that the calculations and handling of NMEA messages would be in one place and not duplicated. Then, as you say, the OD EBL (or a class based on the EBL) could then be used as the basis for drawing the on-screen vectors.

For the drawing side how do we want to handle scale? Should the vectors be to actual scale, should they be a user defined multiplier, should they always be a certain 'pixel' size. Do we want a new OD Toolbar icon or do we want it just 'right click' on chart selectable?

I will have to have a look at the Tacticks plugin to see how the interaction might work.

Jon

[RobertLeask]

Originally Posted by rgleason

Dear Jon,


PS: I would like to encourage RobertLeask to review and advise about the graphical standards for DR representations and notation, so that the DR functions are close to or equivalent to standard procedures, if that is possible Jon?

Hello again. I'm very pleased to see that there is some interest in this problem, but I'm again away from my boat in a landlocked place and have no access to any marine instruments. I recently launched my boat in Florida and now have a working heading sensor, speed log and gps, so when I get back to Florida this fall I'll be able to try things out.

I'm not sure if there is a global standard for the terminology of set and drift, I believe that in the UK they say "set and rate", drift meaning wind drift. In North America "set and drift" is the commonly used term for direction and speed of current. Wind drift is generally disregarded.

As far as I know they use the same notation on the chart everywhere, here's a link to a site with set/drift vectors. RULE OF THE ROAD WITH DETAIL FIGURES AND QUESTIONS WITH ANSWER: September 2012
The reason drift due to tide and wind are generally lumped together is that the wind drift of any given vessel will differ according to wind thrength, course relative to the wind, vessel speed, sea state and other factors, and can only be estimated by extensive testing. It would be nice to know but it complicates things too much.

A Google search turned up lots of online navigation courses, useful for reference.

I would like to participate in developing this plugin, but I'm not a programmer and have no idea how to code. Is it possible an old sailor suffering from too many birthdays could learn enough to help out?