Coordinate System

[patprice]

I need some help in understanding the coordinate system that Rod Heikell uses in his many excellent publications. I cannot find an explanation in his books.

An example would be 39(deg symbol) 09'.07 N 20(deg symbol) 34'.01 E. No problem with the degrees bit, but what is the minutes bit?

The system I am used to is simply degrees and minutes with minutes shown as whole numbers and decimals of degrees. As here...43(deg symbol) 12.12'S 143(deg symbol) 26.76'E. Shown here is two decimal places of minutes.

Can some explanation be given please.

[Omatako]

Is this a trick question?

Rod Heikel says 39.09.07N. Meaning 39 degrees, 9 minutes and .07 of a minute

You say 43.12.12S. Meaning 43 degrees, 12 minutes and .12 of a minute.

What part of that is confusing?

I'm clearly missing something. Maybe it's because he has the ' after the minutes/fractions and you have it after the minutes but before the fraction?

[El Pinguino]

Ah.....

I have always written minutes and decimal minutes thus 39* 54.2' S

However, if you read books like the Admiralty Manual of Navigation they shift the ' to the left so it reads 39* 54'.2 S.

I have never seen it used at sea and think it is pukka sahib Royal Navy stuff ....

At the end of the day .. same thing but different....

Real sailors do it my way.....

( I use * for the degree sign cos its quick and easy )

[TurninTurtle]

Standard global coordinates.... You can type them into google maps and find the spot.

https://www.google.com/maps/place/39...4!4d20.5669444

[El Pinguino]

Originally Posted by TurninTurtle

Standard global coordinates.... You can type them into google maps and find the spot.

https://www.google.com/maps/place/39...4!4d20.5669444

39°09'07.0"N 20°34'01.0"E

I think the google people should stick to 'street view' .. the above makes no sense at all ... decimals of a minute followed by the seconds of arc symbol....????

Its different, I'll grant them that..

[StuM]

For those who don't know - you can enter the degree symbol ° on a Windows PC by holding down the Alt key and entering 0176 on the numeric keypad.

[El Pinguino]

And on a Mac?

[StuM]

Originally Posted by El Pinguino

39°09'07.0"N 20°34'01.0"E

I think the google people should stick to 'street view' .. the above makes no sense at all ... decimals of a minute followed by the seconds of arc symbol....????

Its different, I'll grant them that..

It makes perfect sense. If you want to work in DMS.

It is not decimals of a minute, it is decimals of a second.

39 degrees, 9 minutes and 7.0 second North
20 degree 34 minutes and 1.0 seconds East

How else would you show the location down to 3 meters if you want to use degrees, minutes and seconds?

But that's actually not an accurate representation of that location.

Maps works with locations as decimal degrees to 6 decimal places. If you follow that link and look at the marker, you will see that the location is shown as: 39.151957, 20.566944 which is roughly to the nearest 11cm !

(When someone gives me a Maps location like that, I generally ask them which side of the front door they are referring to )

[StuM]

Originally Posted by Omatako

Is this a trick question?

Rod Heikel says 39.09.07N. Meaning 39 degrees, 9 minutes and .07 of a minute

You say 43.12.12S. Meaning 43 degrees, 12 minutes and .12 of a minute.

What part of that is confusing?

I'm clearly missing something. Maybe it's because he has the ' after the minutes/fractions and you have it after the minutes but before the fraction?

The confusing part is that your interpretation is incorrect.

When a reference is shown with two "dots" and no unit indicators, it is conventionally interpreted as dd.mm.ss so
43.12.12 means 43° 12' 12" not 43° 12.12'

[patprice]

Thanks for the replies..

Am I picking up some confusion? Does the system that Heikell uses really us seconds not just degrees and minutes.

My nav program does not like that. It likes degrees and minutes with decimals of minutes shown. Easy.

[StuM]

Originally Posted by El Pinguino

And on a Mac?

Hissing and making the sign of a cross with my forefingers!


(I believe that Ctrl-Command-Space or Option-K or Option-Shift-8 may work)

[El Pinguino]

Originally Posted by patprice

Thanks for the replies..

Am I picking up some confusion? Does the system that Heikell uses really us seconds not just degrees and minutes.

My nav program does not like that. It likes degrees and minutes with decimals of minutes shown. Easy.

No seconds involved.... both of your examples are using decimal minutes.... Heikall just uses the 'text book' form .... is all

[StuM]

Originally Posted by patprice

Thanks for the replies..

Am I picking up some confusion? Does the system that Heikell uses really us seconds not just degrees and minutes.

My nav program does not like that. It likes degrees and minutes with decimals of minutes shown. Easy.

Most nav programs have an options setting which allows you to choose between decimal degrees, degrees and decimal minutes or degrees,minutes,seconds.

These days it seems to be that astronomers and die-hards are the only ones still using seconds.

[Alan Mighty]

Originally Posted by StuM

Maps works with locations as decimal degrees to 6 decimal places. If you follow that link and look at the marker, you will see that the location is shown as: 39.151957, 20.566944 which is roughly to the nearest 11cm !

(When someone gives me a Maps location like that, I generally ask them which side of the front door they are referring to )

Given that the Australian continent (and likely New Guinea too) is moving at 7 cm a year - about twice as fast as the average growth of fingernails (which supposedly average 3.6 cm a year) - that sort of precision is a tragicomedy like most things in life.


The Australian datum was last updated in 1999. According to today's media release, we're 1.5 metres away from where we were then: Australia's latitude and longitude coordinates out by more than 1.5 metres, scientists say - ABC News (Australian Broadcasting Corporation)

[geoffkimblin]

Extract from Rod's Greek Pilot:-

"All waypoints are given in the notation:

degrees minutes decimal place of a minute

It is important not to confuse the decimal place of a minute with the older 60 second notation."