YOU CANNOT BE LOST WITH SMART PHONE

We know we can find our location with GPS in the smart phone. Let us see how the Geo-positioning system (GPS) works in simple language.

There are circular paths around the earth, and they are called orbits. In GPS system, there are six orbits in different planes across the earth. (see figure). In each orbit, six satellites are going around the earth. Totally, 30 satellites revolve around the earth. At least four satellites will be visible to you wherever you are on this planet.

The satellites continuously send signals. Your GPS phone receive them and calculates the time of travel. Then, using the formula,
satellite's distance = speed of light(signal) * time of travel.
the phone calculates the distance of the satellite.

On receiving signal from one satellite, the GPS in your phone construct sphere of which the satellite is the center. The 'distance' is the radius of the sphere. You are somewhere on the sphere.This information is not enough to find you. If you get another reading from another satellite, you get a second sphere. Both spheres intersect and intersecting area form a circle. (see figure). Now you are somewhere on this circle. Your location info. greatly improved. If you get a third reading from a satellite, three sphere intersects and form a smaller circle and the accuracy of your location further improves. Four satellites give enough accuracy. The GPS software in the phone calculates all this. That is why, we are able to use the google map efficiently. Readings from 10 satellites give location accuracy close to an inch.

Foot note: Satellites send signals with their time stamp.
Einstein theory of relativity is taken into account here.
a. Clocks in the satellite run slowly (milliseconds).
b. clocks in the space are affected.
Hence, due corrections are made by GPS software.

Nobody can hide with working smart phone.

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