Degrees, Minutes, Seconds vs Decimal Degrees

[requiem]

Originally Posted by RaymondR

It was all very simple before the French decided to corrupt it with their metric system.

If you go to the moon or Mars or any other spherical body and apply the same graticular system wherein the base unit of measurement is a minute of latitude at the equator

I'm not sure why references to the equator keep showing up. From Gunter to Eratosthenes the common method was to calculate along a meridian for reasons that should be well-apparent to many sailors. The results of these produce a value that approximates that of the mid-latitudes.

It's a shame that this anglo-gallic peasant rivalry should have over-shouted the attempts by scientific minds on both sides to standardize on a system of measurement. To create a separate system of measures for each planet would be to re-institute the cacophany of units that predated the modern era, when a bushel of oats differed from a bushel of corn, and the length of a foot or yard differed from country to country.

If tradition is desired, what better way to honor the place of Old Earth as our origin than to cement her measures across the stars, so that in millenia hence people might say that their calendar marks the seconds since man first walked on the moon, and that the origin of the meter was relates to the size of humanity's ancient home?

[Shrew]

Originally Posted by Time Theory

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?

IMHO using Degrees, Minutes, Seconds is like someone asking you what time it is and replying "6 Hours, 23 minutes, 17 seconds"

It is both technically correct, and exactly how you were taught. However, is almost pedantic. when "6:20 or 6:25" would have been acceptable.

[ChrisJHC]

Knowing that a nm is about 1.8 km is useful when the weather bureau says the wind will be 20 km/h and you can quickly work out that is around 10-12 knots.

[chrisr]

Originally Posted by ChrisJHC

Knowing that a nm is about 1.8 km is useful when the weather bureau says the wind will be 20 km/h and you can quickly work out that is around 10-12 knots.

m/sec is the unit of wind measurement that annoys me most...although it's easy enough to convert to knots, why not use knots in the first place !

cheers,

[StuM]

Originally Posted by chrisr

m/sec is the unit of wind measurement that annoys me most...although it's easy enough to convert to knots, why not use knots in the first place !

cheers,

Because most wind reporting is on land, and other than for aviation, no one uses nautical miles or knots on land, they use m/s, km/h or MPH?

And it's easier to convert m/s to knots when required rather
tham converting from km/h or MPH

(x2 is close enough to x1.94 and is easier than x0.54 and much easier than x0.87 )

[SeanPatrick]

All of this disagreement is why I have now chosen to measure all of my distances in "sheppeys": 7⁄8 of a mile (1.4 km) or the closest distance at which sheep remain picturesque.

[kmacdonald]

Degrees, minutes, decimal minutes is the standard used today. That uses GPS accuracy to its full extent if using 3 decimal places. Its more precise than degrees, minutes, seconds.

[El Pinguino]

Originally Posted by Wotname

Crikey, if you guys are given an inch, you will take a mile - dunno how long that is though anymore...

I do hope the OP is still with us - so much to learn about how to tell people where you are on the radio.

Time for a true story.

On the drift outside Port Jackson waiting to go up to Gore Bay to discharge. A fine sunny saturday morning.
This was the early 1980s.. either the Amanda or Robert Miller.
VIS Sydney Radio was still on VHF.

Ch 16 'This is SeaWolf ( true name ) .. this SeaWolf..'
Repeated a number of times.
Then 'Seawolf this is Sydney Radio, can I help you?'
'Sydney Radio Seawolf permission to send a Mayday'
'Permission granted'
'Mayday Mayday this is Seawolf'
'Seawolf Sydney Radio what is the nature of your problem?'
'Sydney Radio Seawolf we have broken down and need a tow to Parramatta'
While all this is going on the person on Seawolf is speaking in a higher and higher pitch... in fact sounding a bit panicky.
Sydney Radio advises that they will see what they can do but it may not involve a tow to Parramatta from outside the Heads.
Asks Seawolf what their position is. Voice totally cracks at this stage as Seawolf sez....

'We are very close to the rocks!!!!!!!'

And that ladies and genlemen is how you tell people where you are on the radio.

Lots more where that came from , amazing what you used to hear on the VHF in port approaches.

[Wotname]

Originally Posted by El Pinguino

.........
'Seawolf Sydney Radio what is the nature of your problem?'
'Sydney Radio Seawolf we have broken down and need a tow to Parramatta'
While all this is going on the person on Seawolf is speaking in a higher and higher pitch... in fact sounding a bit panicky.
Sydney Radio advises that they will see what they can do but it may not involve a tow to Parramatta from outside the Heads.
Asks Seawolf what their position is. Voice totally cracks at this stage as Seawolf sez....

'We are very close to the rocks!!!!!!!'

And that ladies and genlemen is how you tell people where you are on the radio.

Lots more where that came from , amazing what you used to hear on the VHF in port approaches.

Well the 1980s were pre-internet so getting travel advice by VHF from the Rocks to Parramatta isn't so far fetched.

Way easier today though https://www.rome2rio.com/map/Parramatta/The-Rocks

More info on the rocks https://www.therocks.com

[El Pinguino]

Originally Posted by

Well the 1980s were pre-internet so getting travel advice by VHF from the Rocks to Parramatta isn't so far fetched.

Way easier today though https://www.rome2rio.com/map/Parramatta/The-Rocks

More info on the rocks https://www.therocks.com

It wasn't those rocks...

[El Pinguino]

Have you ever heard of a racing yacht called Trump Card?

[Wotname]

Originally Posted by El Pinguino

It wasn't those rocks...

[chrisr]

Originally Posted by El Pinguino

I do hope the OP is still with us - so much to learn about how to tell people where you are on the radio.

Time for a true story.

On the drift outside Port Jackson waiting to go up to Gore Bay to discharge. A fine sunny saturday morning.
This was the early 1980s.. either the Amanda or Robert Miller.

now there's a coincidence. i sailed on Amanda Miller around 1978 or so. also Express & Howard Smith. who knows...maybe paths have crossed

deck or engine room ?

cheers,

[RaymondR]

Originally Posted by requiem

I'm not sure why references to the equator keep showing up. From Gunter to Eratosthenes the common method was to calculate along a meridian for reasons that should be well-apparent to many sailors. The results of these produce a value that approximates that of the mid-latitudes.

It's a shame that this anglo-gallic peasant rivalry should have over-shouted the attempts by scientific minds on both sides to standardize on a system of measurement. To create a separate system of measures for each planet would be to re-institute the cacophany of units that predated the modern era, when a bushel of oats differed from a bushel of corn, and the length of a foot or yard differed from country to country.

If tradition is desired, what better way to honor the place of Old Earth as our origin than to cement her measures across the stars, so that in millenia hence people might say that their calendar marks the seconds since man first walked on the moon, and that the origin of the meter was relates to the size of humanity's ancient home?

If you were a navigator of the open oceans in pre satellite navigation days you navigated between geographical coordinates on the graticule and it was far simpler to define the displacement in arc terms and then make the simple calculation to arrive at the distance answer in nautical miles. It was the arc magnitude which defined the distance in nm and not the other way around.

My recollection of the origin of the metre is that it was originally a platinum iridium bar which represented 1/10,000,000 of the distance between the north pole and the equator through Paris which appears to be a sordid copy of the nm at the hands of that grubby little Corsican who ruled France through the barrel of a gun at the time. Whose to say that their measurement of the earths circumference was any better than the English effort at the time.

[El Pinguino]

Originally Posted by chrisr

now there's a coincidence. i sailed on Amanda Miller around 1978 or so. also Express & Howard Smith. who knows...maybe paths have crossed

deck or engine room ?

cheers,

Deck, in the 70's I was condemned to the dirt boats. Was on the Miller ships over about a 2 year period prior to them being sold.