Okay, lots of people either don't know how latitude is calculated or have misconceptions about it. Here is the truth:

The Latitude, like any modern geodetic parameter, is defined in relation to a reference model of the earth's surface. The standard reference surface accepted in the US and most other countries is an ellipsoid of revolution having an equatorial radius (semi-major axis) of exactly 6,378,137 meters and an eccentricity of approximately 0.081819191. Yes, if you didn't know it until now, the earth is not a perfect sphere, it's slightly oblong because it spins.

The Latitude of a point on the reference ellipsoid is defined as the acute angle between the surface-normal at the point in question and the projection of this normal upon the equatorial plane (normal=perpendicular). What this means is, imagine a line pointing from the surface of the earth directly up (with reference to that spot). The angle that the line makes with a line going straight out from the equator is the degree latitude.

Longitude is a lot easier since the earth does look like a perfect sphere when viewed from the north or south pole. It's done exactly how you would imagine: divide the earth into 360 wedges and each one represents one degree of longitude.

Now you know...go impress your friends.

**Physicists Note: The earth isn't really elliptical either. Because the south pole has the land mass of Antarctica and the north pole is pretty much just water, the earth is really pear-shaped. This is a very slight difference though, and because of how much harder the math would be using a pear-shaped model instead of an ellipsoid, pretty much everyone uses the rotating ellipsoid model.

Latitude does affect climate, but only in conjunction with ocean currents and topography. To give you an idea of what places have the same latitude:

90 N: North Pole
80 N: Ellesmere Island, Svalbard Islands
70 N: Murmansk; Barrow, Alaska
60 N: Stockholm; Anchorage, Alaska; St. Petersburg
55 N: Moscow, Edmonton, Copenhagen
50 N: London, Vancouver, Frankfurt, Astana, Khabarovsk, Winnipeg
45 N: Montreal; Belgrade; Vladivostok; Seattle, Washington
40 N: New York City, Madrid, Beijing, Ankara, Samarkand
35 N: Tokyo; Los Angeles, California; Jerusalem; Kabul; Atlanta, Georgia
30 N: Shanghai; Cairo; Houston, Texas; Delhi
25 N: Taipei; Miami, Florida; Dubai
20 N: Hong Kong, Mexico City, Mumbai, Honolulu
15 N: Bangkok, Manila, Dakar, Guatemala City
10 N: Addis Ababa, Caracas, San Jose
5 N: Kuala Lumpur, Bogota, Lagos
Equator: Singapore, Nairobi, Quito
5 S: Natal, Dar es Salaam
10 S: Luanda, Port Moresby
15 S: Brasilia, Lusaka, La Paz
20 S: Townsville, Fiji
25 S: Rio de Janeiro
30 S: Durban, Brisbane
35 S: Buenos Aires, Cape Town, Sydney
40 S: Wellington
50 S: Falkland Islands
60 S: South Shetland Islands
70 S: Antarctic Peninsula
80 S: Vostok Base
90 S: South Pole

Of course, London and Winnipeg have very different climates, as do Miami and Dubai, and Singapore and Nairobi. In the first two cases, this is due to the water: in the last case, it's due to the land.

The moral of this story is: Don't try to predict a location's climate based solely on where it appears on a political map.

Lat"i*tude (?), n. [F. latitude, L. latitudo, fr. latus broad, wide, for older stlatus; perh. akin to E. strew.]

1.

Extent from side to side, or distance sidewise from a given point or line; breadth; width.

Provided the length do not exceed the latitude above one third part. Sir H. Wotton.

2.

Room; space; freedom from confinement or restraint; hence, looseness; laxity; independence.

In human actions there are no degrees and precise natural limits described, but a latitude is indulged. Jer. Taylor.

3.

Extent or breadth of signification, application, etc.; extent of deviation from a standard, as truth, style, etc.

No discreet man will believe Augustine's miracles, in the latitude of monkish relations. Fuller.

4.

Extent; size; amplitude; scope.

I pretend not to treat of them in their full latitude. Locke.

5. Geog.

Distance north or south of the equator, measured on a meridian.

6. Astron.

The angular distance of a heavenly body from the ecliptic.

Ascending latitude, Circle of latitude, Geographical latitude, etc. See under Ascending. Circle, etc. -- High latitude, that part of the earth's surface near either pole, esp. that part within either the arctic or the antarctic circle. -- Low latitude, that part of the earth's surface which is near the equator.

© Webster 1913.

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