Marine logarithm tables

Marine logarithm tables of whole numbers and example of how to use them

Marine logarithm tables:

This page only explains the use of this table, but you need to go to the page ‘Sun’s altitude and logarithm tables at sea‘ to see the full context.

The best way to calculate your position at sea using a sextant and logarithm tables is to start with the exercise ‘La Rochelle.’

After the general first part, make your choice between the calculator or the logarithm method.

Table of Logarithms of whole numbers

These tables were developed by the author with the help of Google Sheets.

The five tables necessary to obtain the calculated height (Hc)

Table 1: log cosine

Table 2: log versine

Table 3: natural cosine

Table 4: logarithms of whole numbers

Table 5: natural sine

Winter Sea Big Waves And Frozen Breakwater. Author image: Michal Szu

Marine logarithm tables:

example table 4: (logarithms of whole numbers)

First part of the worksheet

The inputs obtained in the first part of the worksheet necessary to find the calculated height of the sun (Hc)

L = 16° 09′ N (D.R. latitude)

D = 19°21′,9 S (declination of the sun)

P = 42°15′,1 (NE) (polar angle)

logarithm tables part of the worksheet with solution

The 29,37182 is called log 2e term

TABLE IV

Marine logarithm tables:

Log 2e Term = 29,37182

Mantissa = 37182

Characteristic = 29

The mantissa

With the Mantissa ( 37182), we will search for the whole number in the table of logarithms and whole numbers (Table IV)

Table 4: page 2200 to 2600 PDF Download

Table 4 page 2200/2600

The use of the characteristic is to put the coma!

after finding the whole number, we have to put the comma!

Characteristic is 29 (see below for the coma)

You will find this small table with the characteristics as a reminder on the front page of Table 4.

Whole number = 2345

Characteristic = 29

natural second term = 0,2354

Conclusion: Here we see that we transform natural numbers into logarithmic numbers. Instead of multiplying, we add these logarithmic numbers to obtain a total logarithmic term.

Then, using Table IV (Logarithms of Whole Numbers), we convert this logarithmic term back into a natural number.

It’s like sending our numbers on a log trip and welcoming them back to the world of natural numbers!

L’Île Coco, Cargados Carajos in Mauritius. Author image: MauriceBer

Marine logarithm tables: recall

The purpose is to calculate the height of the sun (Hc) without a calculator.

The use of logarithm tables will replace multiplication with addition.

We will find an example and two exercises completed in the interactive worksheet (tables) page in the calculated Height section.

The idea is to continue with the concept of the DR position, and intercept but we no longer use the rule of signs (positive or negative)

It will be replaced by the notion same name or not same name.

method:

In principle, we adhere to the same Saint-Marc-Hilaire method.

These logarithm tables do not depend on time either.