Is my plot from the manual right?
 

I decided to try the challenge that appears at the end of the manual and I got the following results... which appear to be slightly different than Lurker's with the exception of the intercept which is way different for me assuming a 17kt intercept speed.

In fairness to Lurker, I think he provided those results with a beta version of MoBo that didn't allow for entering speed in tenths of knots.

Would you guys check my plot here and see if you agree with my results or tell me what I've screwed up...

http://www.xl-logic.com/mobo/tutoria...allenge_answer

How you can obtain the CPA, with the 90º tool over the DRM ? I able to plot the rest of the questions.

Once you have the DRM line...

1) Create a new contact
2) Connect contact to OwnShip
3) Set contact heading and speed based on DRM & SRM
4) On the connecting line display D-B-A
5) Position the contact on the DRM line such that the AoB display is 90°


...and there are at least 3 other ways to do it as well. The 90° bars are not used in this example. The only time you'd use the 90° bar tool is if you want to do some offset measurement.

LOL better late than never. Here are my results:

DRM = 45
MRM = 13030yd
SRM = 15.4 kts
CPA = 13445yd
True Course/Speed = 85/14.1 kts
Course/Speed to Intercept = 18/17kts

http://spidermine.com/misc/workedtutorial.JPG

Looks good to me... :up:

Challenge Plot
 

Looking at the first example, the distance plotted from own ship to M1 is 280T and 16500 yards. M2 shows 330T & 14000 yards. It would seem that this plot does not take into account the movement of Own ship for 25 minutes at 10K.

I did not figure that the sub stopped dead when it made the first observation.......

When I plotted it with movement of the own ship, the contact's course came out at 084T, but I can't seem to figure out how to calculate the intercept course and speed.