Subtract Unit
 

Could we please get a subtract vector unit in the next update?

It should function similar to the add vector unit, except it subtracts two velocity vectors. This will be useful to get relative motion from true motion.

Actually, I've been meaning to update the 1.1 beta to allow for that other type of vector addition.

At the moment, all we have is relative to true which is end-to-end vector addition. What we need is a toggle on the Add unit that adds two vectors with the same orgin so we can go from true to relative.

That would be a useful feature for determining (for instance) CPA on a dead reckoning plot.

Lemme take a look and see how easy that one would be to implement. :hmm:
Probably a simple one...

You do realize since you wrote that now it will be the most horribly complex thing ever.... :lol:

Might be able to have this done tomorrow if someone wants to test it. :yep:

The updated version of vb.net uses the newer 3.5 framework. Should be fine for most people...

Alright so my idea was to just add a new tool to the "Add" unit menu called "Subtract".

http://www.xl-logic.com/mobo/tutoria...act_Tool_1.png
...so the menu for the Add unit now includes this "Subtract" toggle. As you can see above, if the Subtract toggle isn't turned on, the add unit performs its normal end-to-end vector addition for unit vectors 1 & 2 (in this case vector 1 is Ownship and vector 2 is the Contact).

http://www.xl-logic.com/mobo/tutoria...act_Tool_2.png
If you change the Subtract toggle to on you'll see the vector addition now shows vectors 1 & 2 starting at the Add unit origin and the resulting vector is shown to start from the endpoint of vector 1 and terminating at the endpoint of vector 2 (again, vector 1 is OwnShip and vector 2 is the contact). Notice the heading of the Add unit is now reported as the heading of the vector 307°.

Previously, if you had to convert true to relative (as in Prob 3 from Chapter 11 - Maneuvering Board" of the US Navy Operations Specialist NRTC) you would've needed to manually do the vector calcs...
http://www.xl-logic.com/mobo/tutoria...H11_Prob3a.PNG
Here we see how you'd calculate DRM when the Add unit didn't have the "Subtract" feature.

Now with the new feature enabled we can do it like this:
http://www.xl-logic.com/mobo/tutoria...H11_Prob3b.PNG
So now we have the ability to convert from true to relative, in the example above you'll notice we're approaching the contact at a relative speed of 25kts and the contact DRM (direction of relative motion) is 307°.

Is this the sort of thing you were looking for?

Perfect! Absolutely perfect! That's exactly what I was looking for. Can't wait to try it out.