Navigation Position Format

[viva]

I have always used the form dd.mm.ss eg N47⁰,30.00 . I recently bought some charting software and the position information is given in degrees and decimal fractions – so above is represented as N47.50000 (this appears to be fixed and not a configuration/settings option) Is this the current standard? Would the coastguard be familiar with a position given in this format?

 

[prv]

Are you sure your first example is degrees, minutes, seconds? Looks like degrees, minutes, and decimal minutes to me.

Degrees, minutes, decimals seem to be the norm at sea. Degrees, minutes, seconds would have been traditional (if they'd gone to that level of accuracy). Degrees and decimal degrees seems to be more common in general software (google maps type stuff, though I don't know if it's what Google specifically use). Assuming your charting program is a marine one, I suspect whoever wrote it was either lazy or didn't really know much about real navigation at sea.

Pete

 

[[70521]]

This new fangled GPS changed everything! 56.000100 -3.004322 is what you might see on some, but they do some division and give you degrees, minute and decimals of a minute. I quite like the format.

 

[nigelmercier]

I recently bought some charting software and the position information is given in degrees and decimal fractions...

If you can't change it, return it as not fit for purpose.

 

[Elessar]

I have always used the form dd.mm.ss eg N47⁰,30.00 . I recently bought some charting software and the position information is given in degrees and decimal fractions – so above is represented as N47.50000 (this appears to be fixed and not a configuration/settings option) Is this the current standard? Would the coastguard be familiar with a position given in this format?

it look like you have degrees, minutes and decimal minutes.

this has become standard.

if it's degrees and decimal degrees, and can't be changed, take it back.

all the above has been said, I just agree and summarise.

So to add 2ps worth,

try going to 49 degrees 9999N
then try going to 49 degrees 5999N

if the latter works and the former fails you are ok )

 

[AntarcticPilot]

There is a standard; ISO 6709 (and equivalent national standards). See http://en.wikipedia.org/wiki/ISO_6709. However, it allows degrees and decimals; degrees, minutes and decimals of minutes and degrees, minutes, seconds and decimals of seconds. The number of digits before the decimal place indicates which is in force - for Latitude, 2 digits means degrees and decimal degrees, 4 means degrees (the first two digits), minutes (the second two digits) and decimal minutes after the decimal point, and finally 6 means degrees, minutes and seconds with decimal seconds.

I will admit that it is probably not widely used outside the internal representations in Geographic formats like GML. I wasn't part of the team that put the 2008 revision together, but I did contribute some comments during the process.

 

[oldbilbo]

"Man is Not Lost"... He is merely hyper-confused by well-intentioned young geeks with their heads up their........

 

[guernseyman]

I have always used the form dd.mm.ss eg N47⁰,30.00 . I recently bought some charting software and the position information is given in degrees and decimal fractions – so above is represented as N47.50000 (this appears to be fixed and not a configuration/settings option) Is this the current standard? Would the coastguard be familiar with a position given in this format?

Looking at your example I would drop that comma. It ain't needed and, one day, could be mistaken for something else.

 

[AntarcticPilot]

"Man is Not Lost"... He is merely hyper-confused by well-intentioned young geeks with their heads up their........

Assuming that means me, thanks for the compliment! Sadly "young" no longer applies, except at heart, and I suspect a fair proportion of the standards community is older then either of us

 

[oldbilbo]

There is a standard; ISO 6709 ..... The number of digits before the decimal place indicates which is in force - for Latitude, 2 digits means degrees and decimal degrees, 4 means degrees (the first two digits), minutes (the second two digits).....

I will admit that it is probably not widely used......

My mini-grump above was not aimed at your goodself, O Glasshoppah! Nevertheless, I find myself thinking that many of those involved in the endless debates re International Standards seem to enjoy a great deal of self-regard - and not all that much for the poor peons who might have to use their prognostications. On occasion they seem to lose sight of reality....

Take the tale above regarding the 'number of digits before the decimal place' used..... "2 digits means degrees and decimal degrees. 4 digits means degrees ( the first two digits )....."

Perhaps I missed something along the way, but in all this 'dumbing down' that's been going on, it appears I've missed the change from 'Three numeral notation' to indicate the relevant number of degrees, as in 'Three two five' and 'Zero eight zero' to something lesser with only TWO numerals to describe degrees i.e up to 99....

Gimme back my lost 261....!

 

[nigelmercier]

Perhaps I missed something along the way...

I didn't follow it either.

 

[Seatrout]

Even in sobriety, my brain has just melted, resolved itself into engine oil and is pouring out my ears and nostrils.

 

[AntarcticPilot]

My mini-grump above was not aimed at your goodself, O Glasshoppah! Nevertheless, I find myself thinking that many of those involved in the endless debates re International Standards seem to enjoy a great deal of self-regard - and not all that much for the poor peons who might have to use their prognostications. On occasion they seem to lose sight of reality....

Take the tale above regarding the 'number of digits before the decimal place' used..... "2 digits means degrees and decimal degrees. 4 digits means degrees ( the first two digits )....."

Perhaps I missed something along the way, but in all this 'dumbing down' that's been going on, it appears I've missed the change from 'Three numeral notation' to indicate the relevant number of degrees, as in 'Three two five' and 'Zero eight zero' to something lesser with only TWO numerals to describe degrees i.e up to 99....

Gimme back my lost 261....!

The standard is SPECIFICALLY for latitude and longitude; not for general measurements in degrees. You only need two digits for latitude; the examples I gave were for latitude. For longitude you need 3, so it does 3,5,7 digits to indicate the nature of the number. Latitudes extend from +90 to -90; longitudes from +180 to -180.

There was widespread consultation before it was adopted; the authors tried to seek out representatives of as many communities as possible (they approached me before I was involved in the standards process). The present standard replaces an even more arcane version, which was extremely prescriptive about the format. The only application I knew of was some forms of data telex.

However, ISO 6709 is really meant for machine readable data rather than for written representations; I would be very surprised to see it in use outside data transmission or data storage systems. If you want clarity in written representations, then the forms

ddd.dddd (degrees and decimal degrees)
ddd mm.mmmm (degrees and decimal minutes)
ddd mm ss.ssss (degrees, minutes, seconds and decimal seconds)

are completely unambiguous and in widespread use.

Of course, the addition of the degrees, minutes and seconds symbols as appropriate will make it clearer.

Although as navigators we are used to using the suffixes N and S or E and W to indicate the hemisphere concerned, it is more usual to indicate it by giving the number a sign; positive for N and E, negative for S and W. Naturally, most of my work involved both being negative! The sign convention is chosen to simplify navigational and geographic calculations.