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Old 12-04-2021, 18:58   #1
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Degrees, Minutes, Seconds vs Decimal Degrees

When I was learning to plot a position on a nautical chart, I used degrees, minutes and seconds. So if by chance, I was hailed on the VHF to state my current position would I need to report it in degrees, minutes, and seconds or convert it to decimal degrees and report it that way? What is the standard protocol?
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Old 12-04-2021, 19:04   #2
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

It will be obvious by the way you state it. (ie X degrees, Y minutes, Z seconds vs X degrees, Y decimal Z minutes)

Decimal minutes are so much easier on a chart, who was torturing you by teaching seconds??
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Old 12-04-2021, 19:14   #3
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

The modern way is just easier ... and I learned the old-fashioned way too.
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Old 12-04-2021, 19:21   #4
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

by far the easiest way is to read yr position off yr chart plotter. these generally (certainly mine anyway) are set up to give position in degrees minutes and decimals of minutes

however really anything is ok if you just state clearly what format you are giving position in

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Old 12-04-2021, 19:39   #5
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

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Originally Posted by Time Theory View Post
When I was learning to plot a position on a nautical chart, I used degrees, minutes and seconds. So if by chance, I was hailed on the VHF to state my current position would I need to report it in degrees, minutes, and seconds or convert it to decimal degrees and report it that way? What is the standard protocol?
Golly.... how old are you?
Degrees and minutes - decimal minutes to the first decimal place in calculations - place have been the norm in the British sphere of influence for well over 60 years.

In calculations use this form S 45º 34.2' ( some may say that should be written thus S 45º 34'.2 )

Deep sea just use the whole minute eg S 45º 34'

Coastal you are better giving bearing and distance **from** a wellknown landmark.

Whatever you do don't use more than the first decimal place... eg '34.234 minutes'
The first decimal place is about 170 metres, the second decimal place is about 17 metres. The third place - 1.7 metres. At which end of the boat did you say you were standing?

That is in latitude - in longitude it will be even less the further you are from the equator.
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Old 12-04-2021, 19:47   #6
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

OK... so are you asking about DMS vs DM.xx or are you asking for straight D.xxxxx?

Most modern Mercator charts, and marine GPSs , use DM.xx, but there are still plenty of DMS charts out there, and my GPS can be set to DMS. Pure digital degrees (D.xxxxx) has come into being due to mapping tools like Google Maps. It's not something I've seen used in practice in the nautical world.
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Old 12-04-2021, 20:21   #7
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

Virtually NOBODY uses decimal degrees in routine navigation... although it is handy for some esoteric calculations because it is easy to convert to radians.

I am pretty sure the original poster is confusing decimal degrees with the use of degrees,/minutes,/decimal minutes. That has become the "routine" usage. It is unlikely that decimal degrees will ever win out, because the fact that on minute of latitude ~= one nautical mile is just too convenient to give up. Nobody really cares any more that one second of latitude ~= 100 yards.

Of course ANY chart plotter can be programmed to display ANY of these formats. If yours does one or the other is not because it is "standard" but you just don't know how to change it...
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Old 12-04-2021, 20:43   #8
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

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Virtually NOBODY uses decimal degrees in routine navigation... although it is handy for some esoteric calculations because it is easy to convert to radians.

I am pretty sure the original poster is confusing decimal degrees with the use of degrees,/minutes,/decimal minutes. That has become the "routine" usage. It is unlikely that decimal degrees will ever win out, because the fact that on minute of latitude ~= one nautical mile is just too convenient to give up. Nobody really cares any more that one second of latitude ~= 100 yards.

Of course ANY chart plotter can be programmed to display ANY of these formats. If yours does one or the other is not because it is "standard" but you just don't know how to change it...

You mean approx 100 ft!
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Old 12-04-2021, 21:47   #9
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

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Originally Posted by BillKny View Post
Virtually NOBODY uses decimal degrees in routine navigation... although it is handy for some esoteric calculations because it is easy to convert to radians.

I am pretty sure the original poster is confusing decimal degrees with the use of degrees,/minutes,/decimal minutes. That has become the "routine" usage. It is unlikely that decimal degrees will ever win out, because the fact that on minute of latitude ~= one nautical mile is just too convenient to give up. Nobody really cares any more that one second of latitude ~= 100 yards.

Of course ANY chart plotter can be programmed to display ANY of these formats. If yours does one or the other is not because it is "standard" but you just don't know how to change it...
Nobody cares that we had a perfectly well thought out system that had survived thousands of years of refinement when they suggested that we divide a longitudinal line up into 2 million pieces and call one a meter just to make everything base 10... cuz heck whoever came up with this base 6,12,24,60 system.... whatever it is

Traditional mariners and GPS programmers will be the last people on earth who know what a foot is.

Not to be foul to land lubbers, but do you have any idea how many people I know who don’t even know what tides are or how the moon, sun, and other planets affect them?

Regardless of being right or easy, I think decimal degrees are probably already more common because of the whole Google and land based GPS. I am willing to bet geocaching is more common than celestial navigation.

I don’t want to sound bent out of shape, but I’ve endured countless peers saying “why do we use these old systems anyway, dividing by 100 is so much easier” as they proceed to do just that on a calculator.... Most of the people I meet are disconnected from reality. Subject for a different time tho.
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Old 12-04-2021, 23:25   #10
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

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Originally Posted by El Pinguino View Post
Whatever you do don't use more than the first decimal place... eg '34.234 minutes'
The first decimal place is about 170 metres, the second decimal place is about 17 metres. The third place - 1.7 metres. At which end of the boat did you say you were standing?
I minute of latitude is 1852 metres so 0.1' is 185, not 170.

A location to 0.1' covers an area of over 34,000 sq m.
(That's 8.5 acres / 3.45 hectares /6.5 US football fields)
That's a lot of bottom if looking for a bommie or small wreck.

Around here we generally plot reef dive locations to at least two decimal minutes (a bit under 350 sq m).
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Old 13-04-2021, 00:38   #11
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

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I minute of latitude is 1852 metres so 0.1' is 185, not 170.

A location to 0.1' covers an area of over 34,000 sq m.
(That's 8.5 acres / 3.45 hectares /6.5 US football fields)
That's a lot of bottom if looking for a bommie or small wreck.

Around here we generally plot reef dive locations to at least two decimal minutes (a bit under 350 sq m).
That may be why I said 'about'.

And a CDF navigator's requirements are entirely different to those of a diver.
3.45 hectares = twice the size of my garden ie not very big... everything is relative.
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Old 13-04-2021, 01:03   #12
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

Standard now appears to be degrees minutes.decimal. This is the way most GPSs seem to be set as standard and to 1 decimal place is really enough for most purposes except perhaps trying to refind a wreck or enter a very narrow channel.
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Old 13-04-2021, 05:12   #13
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

I like to use the units that my chartplotter likes
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Old 13-04-2021, 05:53   #14
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

I've always found base 10 harder to work with.

Things are easier on computers. Base 2, base 8, base 16. All make sense. Just keep doubling or halving.

The whole 360-degree circle thing is a bit of a relic, but it does make the math pretty easy. Lots of ways to divide that up into nice integers. It's sort of almost like base 6.

Base 10 really doesn't have a lot going for it, except for the number of fingers we humans have. I'd like to think we've developed past needing to use those. Sure, it works on paper, or on a calculator. But any base would. For actually grasping quantities, our minds are wired to process groups of 1, 2 and 3. Anything we can double, or divide in half, triple or divide in three makes intuitive sense. We can even process the concept of 1/4 pretty easily. This is why clocks show 12 or 24 hours, and why circles have 360 degrees. It's just easier to divide up into half, quarter or third.
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Old 13-04-2021, 07:05   #15
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Re: Degrees, Minutes, Seconds vs Decimal Degrees

I just call out whatever my Raymarine screen reports.

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