Explanation of Latitude
and Longitude
Globally all places can be located by a combination of two
numbers, the Latitude and Longitude. The numbers measure the angles from the
centre of the earth to a point on its surface. Latitude and Longitude values
are expressed in Degrees(°) which for greater accuracy are in
turn divided into Minutes(‘) and Seconds(“). Each degree is divided to 60
minutes, each minute to 60 seconds; seconds are divided decimally to 1/10s,
1/100s. Latitude and Longitude values are expressed either:
|
Alphanumerically as Degrees Minutes & Seconds |
50°21’34.301”N 004°44’34.195”W |
|
Numerically as Decimal Degrees |
50.359528 -4.742832 |
Lines of Latitude and Longitude are theoretic lines on the
Earth's surface; Latitude lines are horizontal, Longitude lines are vertical.
Consider the spherical shape of the Earth, the North & South Poles and
Equator.
Explanation of Latitude (Lat): The Equator is the Latitude Line of
0 degrees. Latitude values define the angular distance from the Equator to
points North and South of it. From the Equator, there are 90 degrees of
Latitude north to the North Pole and 90 degrees south to the South Pole.
Latitude values north of the equator (Northern hemisphere) are assigned “N” and
are positive values, those south of the equator (Southern hemisphere) are
assigned “S” and are negative values. Lines of Latitude run parallel to the
Equator (hence termed "parallels") and are "equally" spaced (the
earth is not perfectly spherical so variation occurs) in that 1 degree of Latitude is
approximately 69 miles.
Explanation of Longitude (Long): The Prime/Greenwich Meridian is the
Longitude Line of 0 degrees. Longitude values define the angular distance from
the Prime meridian to points East and West of it. There are 180 degrees of
Longitude east and west of the Prime Meridian. Longitude values west of
the Prime Meridian (Western hemisphere) are assigned “W” and are negative
values, those east of the Prime Meridian (Eastern hemisphere) are assigned “E”
and are positive values. Lines of Longitude ("meridians") pass
through and converge at both Poles; every line of longitude crosses the
equator. The 180 degree meridian on the opposite side of the world to the Prime
Meridian, is not “E” or “W”; it is where the east and west hemispheres meet,
the International Date Line. At the equator 1 degree of Longitude is approx 69
miles, but decreases progressively to 0 at the poles where the
meridians converge. Accordingly 1 degree of Longitude varies in size;
this is shown below for the land mass of
|
At Latitude 50 degrees: |
1 degree of Lat = 69.1 miles |
1 degree of Long = 44.5 miles |
|
at Latitude 60 degrees: |
1 degree of Lat = 69.2 miles |
1 degree of Long = 34.7 miles |
The
Shortest Distance using Latitude and Longitude
To calculate the shortest distance between 2 places using
the Latitude and Longitude values of the places, use the "Great Circle Distance
Formula". The formula can be “simplified” by adjusting it to convert
degrees to radians. If you require the distance between the 2 places expressed
in miles, define the radius of the Earth (“R”) as 3963.1, use 6378.7 if you
want the answer in kilometres.
Use data table below to validate your formula and syntax.
The table shows 4 pairs of locations, the Lat/Long values for each “Location 1”
(“From”) and “Location 2” (“To”). The examples use Lat/Long values of locations
in the
|
Location 1 (“From”) |
Location 2 (“To”) |
Distance |
||
|
Lat1 |
Long1 |
Lat2 |
Long2 |
in Miles |
|
52.0 |
1.0 |
55.0 |
-3.0 |
264.7576 |
|
51.0 |
-4.0 |
54.0 |
-1.0 |
242.8831 |
|
56.0 |
-4.0 |
51.3 |
1 |
384.1036 |
|
54.35 |
-5.71 |
55.0 |
-7.32 |
78.5311 |
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