FLAT MAP FROM SPHERICAL EARTH.

We know the importance of google map today. How to make a map? Earth is spherical, how to flatten it? When we look at a piece of land, it looks flat. Because the area is small. Hence making a map of a small town is easy. When we stand at the sea-shore and look at the ocean, we see horizon where the sky seems to meet the ocean. Horizon appears because of earth's curvature.
A map is should be fairly accurate. It should help long distance traveller (ship, airplanes). It should also meet eduction needs. We are going to use projection method for making a map.
Imagine a 'earth globe' made out of glass. And a transparent real map is drawn on it. We also put a powerful LED lamp at the centre of the glass globe. Put a cylindrical lampshade made out of white p[aper around it. The lampshade should be just touching the sides of the globe. Now switch on the LED lamp. A map is projected on the cylinder. But north and south pole cannot be projected. Since the cylinder is open at both the ends. Now cut the cylinder and unroll it. You get a fairly accurate flat map which is real good enough for all practical purposes. This techniques is called Mecator's projection. It is still used and popular one. If we want the map of north and south pole one can use conical shades.

There are many projection methods. Nothing is perfect. There is some distortion in Mercator's method also. The regions near the pole's appear larger and the regions near the equator appears smaller. There is always some error when spherical surface is flattened. (can you flaten the skin of an orange fruit).
Even measuring distance on a spherical surface pose some difficulty. The units of distance measurement like kilometer, mile, yards -all fail on curved surface. Hence we use'nautical mile'.

Globe or sphere is a rotated circle. A circle has angle of 360 degrees. A degree is split into 60 minutes. One minute angle suspend an arc or distance on the surface of the earth. The length of the arc is 1852 meters. That is one nautical mile.
Our world is mostly curved one.
-----------------------------------------------------------------------------------------------------------------------

Comments

THE EARTH, A SUPER ORGANISM

JOIN MY COURSE: "Become a programmer in a day with python" A man called 'love lock' (what a name) proposed a theory called Gaia theory, named after Greek Goddess. It says, "Earth is a self-regulating organism like a human being. The organic life in it interacts with in-organic matter and maintains atmosphere, temperature and environment". Hence the earth is still suitable for the life to thrive. Imagine, in a particular place, there are lot of flowers. Some flowers are white and some are darkly coloured. We know, white reflects light and heat while dark absorbs the same. White flowers can thrive in hot climate. But dark flowers requires cold climate. The absorption and reflection balances and the environment reaches average, warm temperature at which both the flowers can co-exist. This is the essence of "Gaia" theory. On our earth, ...

THE PARABOLA

A jet of water shooting from a hose pipe will follow a parabolic path. What is the so special about parabola. Y= x^2 Draw a graph for the above equation. It will result in a parabola. This parabola is also called unit parabola. Any equation involving square will yield a parabola. Example: Y = 2x^2 +3x+3 (also called quadratic equation) X= 2 and -2, both satisfies the equation 4 = X^2. Parabolic equations always have two solutions. Any motion taking place freely under gravity follows parabolic path. Examples: An object dropped from a moving train, A bomb dropped from flying plane, A ball kicked upwards. If a beam of light rays fall on the parabolic shaped mirror, they will be reflected and brought to focus on a point. This fact is made use of in Dish Antenna, Telescope mirrors, etc. ...

DISORDER IS THE "ORDER OF THE DAY"

Imagine a balloon full of air. The air molecules are moving randomly inside the balloon. Let us pierce the balloon with a pin. The air rushes out. Why should not the air molecules stay inside the balloon safely and ignore the little hole? That is not the way the world works. The molecules always "want to occupy as many states as possible". Hence the air goes out in the open to occupy more volume. The things always goes into disorder (entropy) and the disorder increases with time. The above statement is what we call "second law of thermodynamics". Consider a cup of coffee on the table. Suppose the heat from entire room flows to your cup of coffee, the coffee will boil and the rest of the room will freeze. Freezing means bringing things to order and arrangement. It violates the second law. Hence it will never happen. Hence heat must flow from high ...

sciencecapsules

Search This Blog