[TMO] nav maps distance/speed charts

Frederf · 08-20-09, 01:26 AM

I think it's too easy to overestimate the complexity of the nomometer and treat it like it's some black voodoo magic. All it does is calculate time, speed, or distance if you know the other two things.

"How much time does it take to go a distance at this speed?"
Time = Distance / Speed

"How much distance is traveled by going speed for time?"
Distance = Speed x Time

"How fast does something have to go some distance within this much time?"
Speed = Distance / Time

These are the only three questions that the nomometer knows how to answer. If you want to know the course or angle or when the moon will rise, you need to look somewhere else. You ask by drawing a straight line through the two values you do know and the answer is discovered by finding where the line crosses the scale of the value you want to find out.

A practical example is (for me) commonly that I have plotted the target's location and I know its course and speed through previous calculations. I've decided that I want to shoot at the target when it gets to some specific future position since that makes for a good shot with short range and good angles. So I measure the distance from the target's current position to the desired future position and maybe it's 4600yd. Also say for example that the target is going at 8 kts. What I want to know is "How much time is it going to take that 8 kt ship to travel 4600yd?" This is important to me because I want to know how long I have to get into shooting position.

I pull out the ruler tool on the navigation map and I start a line from the 8 kt mark on the speed scale. I pull this line through the 4600yd mark on the distance scale until I cross the last scale, time. I notice that this line that passes through "8kt" and "4600yd" also passes through about 17 minutes. This tells me that something takes 17 minutes to go 4600yd at 8 kt.

Just for fun the problem can be extended. Using the previous result of 17 minutes until the target gets where I want him to be for shooting I discover that my submarine is too far away to make a shot. Oh no! Now I pick where I want to be to shoot which I measure to be 1200yd away from my current position. OK, I have 17 minutes to go 1200yd. How fast do I have to go? Leaving the right end of the line I made in the paragraph above at 17minutes, I drag the left end of the line around until the line crosses through 1200yd mark on the range scale. Then I look to the speed scale to figure out my unknown. The line crosses the mark at just over 2 kts. "I must go 2 kt to travel 1200yd in 17 minutes."

17 minutes later the 2 kt submarine has traveled its 1200yd and the 8 kt target has traveled its 4600yd. The nomometer has allowed me to arrive just in time.

magic452 · 08-20-09, 02:43 AM

Frederf's little tutorial is also useful when a convoy is changing course every 20NM. or so. Can I get a good position before they change or should I take a different track and attack after the course change?

Having time to set up for a good shot is the best way to get a good result.

Magic

Frederf · 08-20-09, 08:41 AM

It's also nice to get the timing right to slip in the escort screen gaps or if you ascribe to the "can't sit at perfect periscope depth at 0 knots for days on end" realism.

Rockin Robbins · 08-20-09, 08:44 AM

Actually it's a nomograph, not a nomometer. A meter is a mechanical device.

DigitalAura · 08-20-09, 10:01 AM

Again, my hats off to you all. Wonderful application, Frederf! Thanks.

Pisces · 08-20-09, 11:49 AM

Quote:

Originally Posted by Rockin Robbins

Actually it's a nomograph, not a nomometer. A meter is a mechanical device.

To be even more precise. It's a measurement device.

Frederf · 08-21-09, 12:26 AM

Yeah, something seemed weird writing "nomometer." It's not really a measurement device (which is what the meter suffix would suggest) but a picture or graphic thus "graph."

tomoose · 08-22-09, 10:21 PM

Frederf's explanation is spot on. I had forgotten to mention that the nomograph can help you figure out your own speed/time in order to get to the right spot.

As Frederf says the nomograph gives 3 pieces of information (speed, time, distance), if you have two pieces of that info the nomo will quickly and easily give you the third.

For what it's worth; you'll get to instinctively know what "slow", "medium", "fast" means which will help you pick a speed. I always use 5 knots or less when I get a "slow" report. Having said that I always add a couple of knots to my speed 'guess' so that I have more chance of being ahead of an intended target (i.e. calculate he's moving faster than he actually is and you'll theoretically get there well ahead of him) and then I'll head back down the enemy's plotted course and hopefully intercept. It generally works well but not always as the target could change course, even slightly, and that'll throw things off, but you have to take that chance. No guts, no glory, LOL.

08-20-09, 02:43 AM	#2
magic452 Sea Lord Join Date: Sep 2007 Location: Reno Nevada USA Posts: 1,860 Downloads: 85 Uploads: 0	Frederf's little tutorial is also useful when a convoy is changing course every 20NM. or so. Can I get a good position before they change or should I take a different track and attack after the course change? Having time to set up for a good shot is the best way to get a good result. Magic __________________ Reported lost 11 Feb. 1942 Signature by depthtok33l

08-20-09, 08:44 AM	#4
Rockin Robbins Navy Seal Join Date: Mar 2007 Location: DeLand, FL Posts: 8,900 Downloads: 135 Uploads: 52	Actually it's a nomograph, not a nomometer. A meter is a mechanical device. __________________ Sub Skipper's Bag of Tricks, Slightly Subnuclear Mk 14 & Cutie, Slightly Subnuclear Deck Gun, EZPlot 2.0, TMOPlot, TMOKeys, SH4CMS

08-20-09, 10:01 AM	#5
DigitalAura Straight and True Join Date: Jul 2009 Location: CANADA Posts: 276 Downloads: 8 Uploads: 0	Again, my hats off to you all. Wonderful application, Frederf! Thanks. __________________ ... ALL YOUR BEACH ARE BELONG TO US! ...

08-22-09, 10:21 PM	#8
tomoose Grey Wolf Join Date: Aug 2005 Posts: 930 Downloads: 23 Uploads: 0	Nomograph Frederf's explanation is spot on. I had forgotten to mention that the nomograph can help you figure out your own speed/time in order to get to the right spot. As Frederf says the nomograph gives 3 pieces of information (speed, time, distance), if you have two pieces of that info the nomo will quickly and easily give you the third. For what it's worth; you'll get to instinctively know what "slow", "medium", "fast" means which will help you pick a speed. I always use 5 knots or less when I get a "slow" report. Having said that I always add a couple of knots to my speed 'guess' so that I have more chance of being ahead of an intended target (i.e. calculate he's moving faster than he actually is and you'll theoretically get there well ahead of him) and then I'll head back down the enemy's plotted course and hopefully intercept. It generally works well but not always as the target could change course, even slightly, and that'll throw things off, but you have to take that chance. No guts, no glory, LOL.

08-20-09, 01:26 AM	#1
Frederf Seasoned Skipper Join Date: Apr 2005 Posts: 665 Downloads: 79 Uploads: 1	I think it's too easy to overestimate the complexity of the nomometer and treat it like it's some black voodoo magic. All it does is calculate time, speed, or distance if you know the other two things. "How much time does it take to go a distance at this speed?" Time = Distance / Speed "How much distance is traveled by going speed for time?" Distance = Speed x Time "How fast does something have to go some distance within this much time?" Speed = Distance / Time These are the only three questions that the nomometer knows how to answer. If you want to know the course or angle or when the moon will rise, you need to look somewhere else. You ask by drawing a straight line through the two values you do know and the answer is discovered by finding where the line crosses the scale of the value you want to find out. A practical example is (for me) commonly that I have plotted the target's location and I know its course and speed through previous calculations. I've decided that I want to shoot at the target when it gets to some specific future position since that makes for a good shot with short range and good angles. So I measure the distance from the target's current position to the desired future position and maybe it's 4600yd. Also say for example that the target is going at 8 kts. What I want to know is "How much time is it going to take that 8 kt ship to travel 4600yd?" This is important to me because I want to know how long I have to get into shooting position. I pull out the ruler tool on the navigation map and I start a line from the 8 kt mark on the speed scale. I pull this line through the 4600yd mark on the distance scale until I cross the last scale, time. I notice that this line that passes through "8kt" and "4600yd" also passes through about 17 minutes. This tells me that something takes 17 minutes to go 4600yd at 8 kt. Just for fun the problem can be extended. Using the previous result of 17 minutes until the target gets where I want him to be for shooting I discover that my submarine is too far away to make a shot. Oh no! Now I pick where I want to be to shoot which I measure to be 1200yd away from my current position. OK, I have 17 minutes to go 1200yd. How fast do I have to go? Leaving the right end of the line I made in the paragraph above at 17minutes, I drag the left end of the line around until the line crosses through 1200yd mark on the range scale. Then I look to the speed scale to figure out my unknown. The line crosses the mark at just over 2 kts. "I must go 2 kt to travel 1200yd in 17 minutes." 17 minutes later the 2 kt submarine has traveled its 1200yd and the 8 kt target has traveled its 4600yd. The nomometer has allowed me to arrive just in time.

08-20-09, 08:41 AM	#3
Frederf Seasoned Skipper Join Date: Apr 2005 Posts: 665 Downloads: 79 Uploads: 1	It's also nice to get the timing right to slip in the escort screen gaps or if you ascribe to the "can't sit at perfect periscope depth at 0 knots for days on end" realism.

08-21-09, 12:26 AM	#7
Frederf Seasoned Skipper Join Date: Apr 2005 Posts: 665 Downloads: 79 Uploads: 1	Yeah, something seemed weird writing "nomometer." It's not really a measurement device (which is what the meter suffix would suggest) but a picture or graphic thus "graph."