writing down gps co-ords in log book. how do you do it?

[sailfish 0]

Do you do lat first? or long? Our chartplotter reads off lat then long and thus we write it down that way. I have a program that expects it the other way and it annoys me reading from the log book the other way every single time. Are we writing it down against the norm or is this program expecting it aginst the norm?

[Guest]

I have always done lat/long, don't know why, just have. Anyone else?

[TimB 7]

Latitude first then longitude, never had it questioned.

However do you say/write S41degrees xxx or 41degrees xxxxS? (S=south in-case...) Does it matter?

 

TB

[John B 106]

Its always lat long surely.

 

long lat sounds like something you buy in ponsonby.

[PaulR 3]

Latitude is ALWAYS written FIRST.

 

Once upon a time, seafearers could easily determine their Latitude very accurately. So this was always written FIRST as it was the most important and correct piece of information.

 

The ancient tribes, phonecians, egyptians, polynesians etc all used latitudes, one of the simplest ways being 3 holes in an object (coconut). View the horizion though two holes and if the third hole has the named star you want, then you are upon that latitude of that star and only have to sail east or west to get home . . . eventually.

Having a "named" set of coconuts on board with 3 holes made when at that island previously, made it easy to get there again.

 

Longitude was always a guess and for some still is. This is one of the reasons Capt. James Cook on the bark Endeavour was sent to observe the transit of Venus (against the Sun) so he could measure how long it took to determine the size of the Sun and the distance from earth to the sun with greater accuracy.

 

So Latitude was accurate and written first but Longitude was a lot of guess work and unreliable and so was written second, as the next best guess.

 

Charts used to be based upon the capital of the country of origin. There is an early chart of Auckland and its volcabnoes which has longitude of Greenwhich across the top and Longitude east of Paris on the bottom, so either set of tables could use the same chart. I only have a B&W framed one, but the Waipua Lodge in Mt Wellington had a wall sized coloured version.

 

Longitude was only able to be determined if, and it was a very big IF, you new the accurate time to determine how far around the earth the sun had relatively travelled to where it was when you took an observation, to solve the spherical equation to determine your distance and direction from the suns geographical position at that instance of time.

 

The Lords of the Admiralty put up a major financial prize to encourage an accurate time piece to be developed, one that could cope with heat and cold, humidity and dryness, vibration and rough handling when at sea etc.

 

Harrison was eventually rewarded and (I think) his 2nd & 3rd clocks (but not his first) are on display at the Naval Museum at Greenwich, at the bottom of the hill from the observatory.

 

They are fairly large in today's terms. Think of a metal triangle about the size and depth/thickness of a small desk bureau of drawers / bath / large shower base, full of pinions, gears etc. I was very impressed when I saw them but it would take a couple of men to lift one.

 

Later models became smaller, just like wireless radios to transistors to ear pieces.

 

For a really good read, try "The Illustrated LONGITUDE by Dava Sobel and William J.H. Andrewes", published by The Forth Estate Ltd, London ISBN 1-84115-233-1

 

Thus getting accurate time by firing cannons at NOON from flagships of the fleet, harbour forts, dropping the time ball in port e.g. Lyttleton but recently damaged, was then superceded by the "time pips" on the radio. The most important in NZ was the 1100 time pips which is why there is 3 sets so that you can more accurately observe note and adjust for any errors in your clocks used for navigation. Therefore a sun sight taken mid-morning say 1000 can have the time error checked at 1100 and before the noon sight at say 1214. Thus your position will have a higher degree of accuracy as you can work the calculations with a better deck watch error adjustment, than relying upon yesterdays error adjustment.

 

Even today, GPS accuracy whist greater that previous methods, still has errors "HDOP" being the one most discussed.

 

HDOP = Horizontal Dilution Of Precision

It is a parameter indicating the precision of the positioning system (GPS).

The smaller HDOP value indicates higher position accurately.

 

The GPS fix accuracy is due to the locations of 3 satellites in the sky. High accuracy is obtainable when the satellites are widely scattered in the sky; on the contrary, accuracy is reduced when the satellites have gathered in a narrow space.

 

What program do you have ??

[Guest]

Second that book - excellent reading!!!!!!!

[Guest]

Probably not that important unless someone is out looking for you!!?? But the chart/ GPS Geodetic reference should be used when giving coordinates. Most are set to WGS84, but then there's.... 72, 60, 66??? I think a heap of others too that could put a location many nm out!!!??

[Guest]

Lat then Long, even though have always done it that way I still insist on N/S and E/W prefix, probably a throwback to the "sungun" days

[rigger 47]

36deg 57'.5 S

174deg 15'.2 E

 

When studying Nav early on I was taught that the minute symbol goes after the whole minutes.

Have never bothered with noting the Datum in the log book (if they look at the chart they can get it there), but on position reports I do include it. When recording positions in my records for future plnning I also note the datum originally used and include a range and bearing to a near object.