Re: Programming the 49g+ - radar plotting

In article <Y8WdnZvKTI-2hGve4p2dnA@xxxxxxxxxxx>,
Dagfinn Kristiansen <dakrist@xxxxxxxxx> wrote:

Im new to programming on the hp49g+ - reading sysrpl manuals, trying to
figure out what to do...

Can anyone help me in right direction. Here is my challenge;

Im studing for deck officer, and one of my task is to plot objects
(ships) on the radar screen. Lets say i got one plotting at a point and
6 minutes later i got another plot for same object.

(p1) 8nm 50deg
(p2) 5nm 30deg

The radar operate in degrees (360).

I know there is several ways to find CPA (closest point of approach) and
TCPA (time to...) but im not able to figure out where to begin making a
program for this task.

In a real situation we use a plott ***, drawing lines beween the
points, reading the numbers right off the ***.

Since i own a hp49g+ i want that to be my backup for faster result.

I know this "Radar plotting" program exist on several platforms (TI,
Casio), but i cant find anyone for HP.

Help for a start anyone??

Regards
Dagfinn Kristiansen
(broken email, reply here)

Assuming that you are stationary and that the taget is moving at
constant speed in a straight line:

Given (p1) at range a on bearing A
And (p2) at range b on bearing B
Then (p3) at range c on bearing C will be the CPA
provided that a*cos(A-C) = b*cos(B-C) = c

Also, the distance covered by the target between (p1) and (p3)
will be a*sin(A-C), and the distance between (p1) and (p3) will be
b*sin(B-C), with times between points being proportional to those
distances.

With list of equations
{'a*cos(A-C) = b*cos(B-C)' 'a*cos(A-C) = c'} stored in 'EQ'
you can use 30 MENU to start the equation solver.

If you want your angles in degrees, be sure to have the degree mode set.

Hope this gives you your start.
.

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