Does anyone have an equation to calulate travel time?

As an example I need help with my intercepts. I see a convoy moving at X speed at Y bearing. How can I calculate how long it will take to travel a certain distance so I can plot an intercept better? I need to be able to figure out how long it takes to travel a certain distance at certain speeds so I know if I will be fast enough or whatever to get at the target, ahead or behind. Whatever the case may be.

[LeeVanSpliff]

Originally Posted by Flamingboat

As an example I need help with my intercepts. I see a convoy moving at X speed at Y bearing. How can I calculate how long it will take to travel a certain distance so I can plot an intercept better? I need to be able to figure out how long it takes to travel a certain distance at certain speeds so I know if I will be fast enough or whatever to get at the target, ahead or behind. Whatever the case may be.

I'll have a go at it ... please you guys let me know if I get something wrong.

The speed is in knots, nautical miles per hour. Let's call that S. The distance travelled we'll call D - if that's in nautical miles it will be a lot easier.

Time in hours is T.

Speed is the distance covered divided by the time it took to cover it, i.e. S = D / T

If I read you right you want the time it takes.

That'd be T = D / S.

So to find the time it takes to travel some distance you take the distance in nautical miles and divide it by the speed in knots.

If you're using kilometers you can convert to nautical miles by dividing with 1.85 (1 nautical mile = 1.85 km if I'm not mistaken).

[Orion2012]

You mean like a nomograph??

Or do you want something that calculates speed??
If you time the contact for 3 minutes, then measure the distance moved and divide by 100, you'll get there speed in knots.

With a nomograph you could do the following.

Let's say the contact has been measured for 2 mins, and moved 1200yrds. Draw a line on the nomo connnecting the distancc and the time point, and they will cross, the speed line, at the targets appox. speed. You can use a nomo to figure. Either Speed, distance, or time to move X distance, as long as you have the other variables.

A nomo is included in TMO...not sure what else might include one.

[Frederf]

Originally Posted by Flamingboat

As an example I need help with my intercepts. I see a convoy moving at X speed at Y bearing. How can I calculate how long it will take to travel a certain distance so I can plot an intercept better? I need to be able to figure out how long it takes to travel a certain distance at certain speeds so I know if I will be fast enough or whatever to get at the target, ahead or behind. Whatever the case may be.

Having a Nomograph on your nav map helps a lot with these calculations. It should be very easy to add on to yours even if you don't want to install a huge mod package.

Bearing and Speed is not enough information to plot an exact intercept. You're going to need his position, course, and speed to predict his motion. The first thing I do is mark his current position and a line representing his future motion. Then I make a mark at where I want him to be when I arrive. This is the distance he's going to move; divide that by his speed (using nomograph or a pocket calculator). This shows you how much time you have to get in position.

Armed with how much time you have, mark where you want to be when the target arrives at his mark. Measure the distance between you and that mark. This is the distance you have to cover in the time we already know. Now you calculate a required speed to do that. Speed = Distance / Time.

One trick to know if it's working is that the relative bearing of the target will remain constant for collision courses. If you want to arrive slightly ahead of the target, the bearing better be moving more toward the size. If you want to arrive slightly later to the target, the bearing should start to drift toward your bow.

Usually we draw an intercept at right angles to the target's course although attacks done 45 degrees into the target reduce your chances of detection and a few degrees away can stretch an intercept that you wouldn't have been able to reach otherwise.

I can get their speed and course no problem. It's the intercept. Right now I have a convoy near the Philipines. They are 16 NM away and heading SW. I don't want to just point at them and hit the gas. I want to head SW as well closing the gap. If I can figure out how long it will take them to reach a certain point I can compare it with mine. That way I know if my speed and coarse is the best way to catch up to them. I have to be spart since they have a decent lead so that is where the math comes in.

So knots is nautical miles per hour?

[joegrundman]

Originally Posted by Flamingboat

I can get their speed and course no problem. It's the intercept. Right now I have a convoy near the Philipines. They are 16 NM away and heading SW. I don't want to just point at them and hit the gas. I want to head SW as well closing the gap. If I can figure out how long it will take them to reach a certain point I can compare it with mine. That way I know if my speed and coarse is the best way to catch up to them. I have to be spart since they have a decent lead so that is where the math comes in.

So knots is nautical miles per hour?

yes

mathematically precise intercepts

http://www.subsim.com/radioroom/showthread.php?t=88961

[Monica Lewinsky]

Originally Posted by Flamingboat

As an example I need help with my intercepts. I see a convoy moving at X speed at Y bearing. How can I calculate how long it will take to travel a certain distance so I can plot an intercept better?

I use pen/pencil, paper, protractor, and brain - the thing above the shoulders and ears and the sides - I think you have one, too.

I, occasionally, cheat by using a calculator to save on the paper.

Using the games mapping tools is where I do my thinking/plotting minus calculations works for me.

[Mush Martin]

How about using a ruler on the mapscreen to measure
out the necessary eight or twelve nautical miles, then
use your waypoint to angle into the intercept set
your speed to arrive at the end of the Hour Line
in 45 mins ask your navigator how long to get there
at current speed.
presto.

(times and distance may very some limtations apply void where prohibited
by maritime law)

Originally Posted by Monica Lewinsky

brain - the thing above the shoulders and ears and the sides - I think you have one, too.

Ohhhhh, we wanna hit people with gaaaaarbage cans.....

[XLjedi]

If interested, I have a tool that I use to plot intercepts and other attack stationing problems. There's a link to it in my signature...

If you really want to know the raw math, I also layed that out in a spreadsheet on the MoBo forum; but most people don't really want the equations.

My answer is one word. Nomograph! I only used it to determine speed. I just noticed you can drag time down on the right to get the distance in NM. I'm retarded!

So 5 knots = 5 nm in 60 minutes. Got it. Back to sailing! I didn't even notice the nomograph because I only used to use it for 3 minute speed plotting.

[LeeVanSpliff]

Originally Posted by Monica Lewinsky

I, occasionally, cheat by using a calculator to save on the paper.

Sure! Blame your lazy behaviour on the environmentalists! :p

[Pisces]

Originally Posted by joegrundman

yes

mathematically precise intercepts

http://www.subsim.com/radioroom/showthread.php?t=88961

(excitedly points to that link)

To make sure I do not miss him or have to sprint ahead of him after making visual contact I first project his current position along his course based on the time since the contact report appeared, and estimated speed. Then I extend this with 16km (=max visual range in sh3, use whatever feels good in SH4) by using a circle to build-in my advance position. And only then do I start drawing the sub-contact leg against that circle to make dantenoc's intercept triangle. All the while I assume he's going by the highest speed of that speed-range. And i adjust/recalculate my intercept if the weather slows me down enroute.

Once you make visual or hydrophone (most likely) contact with it, draw that direction the map (10-20 NM, I don't know the limits of SH4 visual/sonar range). Then measure the distance from the old contactreport (old by now.. you did mark it, did you?) upto that visual/hydro bearing line and divide by the time since the old contact report was issued. Measure this with a circle tool so you can see where it touches the line. That would indicate the minimum (average) speed of the contact but also measure upto the furthest end of the bearingline and upto your sub. This can get you a pretty accurate estimate on the speed of the contact.

[seafarer]

Originally Posted by Flamingboat

As an example I need help with my intercepts. I see a convoy moving at X speed at Y bearing. How can I calculate how long it will take to travel a certain distance so I can plot an intercept better? I need to be able to figure out how long it takes to travel a certain distance at certain speeds so I know if I will be fast enough or whatever to get at the target, ahead or behind. Whatever the case may be.

Just download and use MoBo - whole forum dedicated to it at the bottom of the main forum listings.

[Rockin Robbins]

Originally Posted by aaronblood

If interested, I have a tool that I use to plot intercepts and other attack stationing problems. There's a link to it in my signature...

If you really want to know the raw math, I also layed that out in a spreadsheet on the MoBo forum; but most people don't really want the equations.

Beat me to it. Aaronblood's MoBo—electronic maneuvering board and pizza maker!