Questions

[pabrides]

This post has several parts so bare with me please.  If these subjects came up before I have not seen them.

1.    I just learned that the 2017 PRACTICAL NAVIGATOR (Bowditch) is available.  I downloaded it here and looked over a few chapters - it's really a wonderful piece of work..  If a young person was only interested in the sea this pub would give him everything he needs to function as a well rounded sailor in several disciplines.  There is so much information the format now includes a second volume.

2.    I know this forum is about CN, but forum members might also be interested in the other arts of navigation as well - I am, anyway.  However, I'm having trouble finding good examples on how to use the Haversin tables.  I know what a haversin is and the actual formula to find distance between two points, but an example of table use has not come to my attention... Has anyone a clue??

3.    I dont know how well I can explain this, but the calculator in my cell phone (CP), which includes trig functions, does not arrive at the same answer as my electronic calculator or trig function tables.  I have been learning, for the first time, how to use these tables as well as log tables with great satisfaction and fun, but my CP calculator really threw me for a loop when the Sin, Cos, and Tan functions spit out different numbers than what the purpose-built electronic calculator or tables say. 

For example:  Sin 40

Scientific Calculator - .64279  (rounded up)
Trig function Table -  .64279
Cell Phone calculator - .74511

I can find no options in the Cell Phone calculator which might give me a clue as to why the numbers are not the same...  Any Thoughts???

4.    I would appreciate if anyone could give me a few plain examples on how to use the traverse tables.  Meridional parts and conversion, Log of trig, and Amplitude tables also give me trouble...  I have no idea as to their use.

I may not be much of a navigator or mathematician, but its not for want of trying... :) My goal is to acquire the same skills as those navigators who plied their trade before the advent of batteries and electronics. Dont get me wrong - I appreciate the modern convenience of GPS and all the other cool navigation stuff, but give me a Gunter scale and some tables to occupy my free time and Im as happy as a sailor with a beer in one hand a cute girl in the other.

Thanks in advance
joe

[LouisC]

Joe,

Thanks for telling us about the updated Bowditch.

As to Haversins, can't help you much about that for finding the distance between two points. I use this formula for that;

Distance = 90 – Sin -1 (sin(Destination latitude) x sin(Your present latitude) + cos(Destination latitude) x cos(Your
present latitude) x cos(Difference in longitude between Your Location and Destination Location)

Multiply answer by 60 to get Nautical miles.

The "Sin-1" means arc-sin.

A Casio calculator is the only calculator I use- cellular phone one isn't convenient or easy.

Are you trying to find a Great Circle route and waypoints? Pub. No. 229 presents a way to do that.

As to electronics. Ugh, yesterday I was trying to tighten a bolt on the boat trailer hitch and needed the ol' trusty flashlight. Would the batteries work?! Of course not! I was "on the hard" but was a' cussin' like a sailor.

Lou

[pabrides]

Thanks for telling us about the updated Bowditch.  

 Distance = 90 – Sin -1 (sin(Destination latitude) x sin(Your present latitude) + cos(Destination latitude) x cos(Your
present latitude) x cos(Difference in longitude between Your Location and Destination Location)
 
 As to electronics.  Ugh, yesterday I was trying to tighten a bolt on the boat trailer hitch and needed the ol' trusty flashlight.  Would the batteries work?!  Of course not!  I was "on the hard" but was a' cussin' like a sailor.

Lou

I thought perhaps 2017 Bowditch might be old news.... your welcome

Your formula seems similar to the one for finding Hc.  Ill try it for fun, but I still want to learn the haversin table as well as all the nav tables no longer popular.

As a side note; last week one of my English students volunteered to work long (5 significant digit) math problems by hand while I used the log tables.  I consistently worked the problems in half the time with fewer errors.  The log tables work well.

I read that with distances of <600 miles the difference between the great circle and mercator is insignificant, and even at the longest distances the difference is still only about 4 percent; which might be significant in aviation terms, but to ships at sea very little. 

I laughed at your loose bolt experience; "...cussin like a sailor." 

While in the Navy, especially at sea, I always carried a flashlight on my hip in a Velcro loop holster for emergencies - and I made triple sure it was working (the idea of being caught below decks in a darkened ship scared the bejeezes out of me).  Nevertheless, I went to use the flashlight in my tool box a month ago and it was flat dead... I still haven't replaced the batteries..  Its funny how our priorities change.

joe