Coordinates

Ancient Mariners, using charts

Degrees Minutes and Seconds:
for instance: Lat 34°27'36" Long 138°5'26"
or Lat 34°27'36"S Long 138°5'26"E

More Recent Mariners, using GPS
(and charts)

Degrees Minutes and Seconds:
for instance: Lat 34°27'36" Long 138°5'26"
or Lat 34°27'36"S Long 138°5'26"E

or

Decimal Degrees:
for instance:Lat 34.152° Long 138.626°
or Lat 34.152°S Long 138.626°E

or

Degrees and Decimal Minutes
for instance:Lat 10°27.36" Long 138°6.26"
or Lat 10°27.36"S Long 138°6.26"E

or

Degrees Minutes and Decimal Seconds:
for instance: Lat 34°27'36.5" Long 138°5'26.3"
or Lat 34°27'36.5"S Long 138°5'26.3"E

NOT

Degrees Minutes Seconds and Decimal(? Seconds):
for instance: Lat 32°59'46".04 Long 137°46'07".27
What units are the decimal values?

GPS Data Transfers - WGS84
(and some chartwork)

Decimal Degrees:
for instance: 34.1523 138.6265

GPS UTM Format MGA94
(Used in South Australian Waters Atlas and some chartwork)
Australian Map Grid based on AGD66 (Obselete, used by UBD)

(Horizontally coincident with WGS84)
Decimal Degrees from a stated datum (Zone):
for instance:UTM 487100E 6237335N Zone 54
 or 275 E 6147 N
Note difference between AMG and MGA is about 200m N E

Notes

In chartwork, symbols follow decimal values
For data input, fields may require other formats

Positional accuracy

1 minute of Latitude = 1 nautical mile
1 second of Latitude = 30.86 metres or approx 100 feet
0.1 seconds = 3 metres
0.01 seconds = 30cms or approx 1 foot
0.001 seconds = 3cms or approx 1 inch
0.0001 seconds = 3mm or approx 1/8 inch

Some Equivalents

One Nautical Mile

6076.1 feet
1852 metres
1.150 miles

One Knot

1.688 ft/sec
30.87 metres/minute
1.1508 mph

One Fathom

6 feet
1.828 metres