1. LATITUDE
Where am I?
On the open sea, there are no landmarks.
You could be anywhere.
To know your position you need to find your
longitude and latitude.
Latitude is your position north or south of the
equator.
Lines of latitude are all parallel to each other, so
they are often referred to as “parallels”.
You can find your latitude by measuring the
height of the Sun above the horizon at Noon.
The closer you are to the equator, the higher the
Sun appears in the sky at Noon.
The further you are from the equator, the lower
the Sun appears in the sky.
By measuring the angle between the horizon and
the Sun at Noon, you can calculate your latitude.
If you are north of the equator, you can find your
latitude at night by measuring the height of the
Pole Star, instead of the Sun.

2. LONGITUDE
Where am I?
On the open sea, there are no landmarks.
You could be anywhere.
To know your position you need to find your
longitude and latitude.
Longitude is your position east or west.
But east or west of what?
Unlike latitude, there is no natural “zero-line” to
measure from.
So, we choose a line of longitude – or “meridian”-
as our starting point.
Longitude 0° - the Zero Meridian of the World –
runs through the Royal Observatory Greenwich.
You can find your longitude if you know the
difference between the time where you are and
the time in Greenwich at that same moment.
Since the Earth spins, only part of it faces the
Sun at any time.
So different places around the world are on
different times of the day.
If it is Noon at Greenwich, it is midnight on the
other side of the world.
And one hour’s time difference between two
places is same as 15° of longitude.