**Azimuth**: an angular measurement in a spherical coordinate system.

Example: An azimuth is the measurement of the position of a star in the sky. the star is the point of interest, the reference plane is the horizon of the surface of the sea.

The azimuth is the angle between the north point and the perpendicular projection of the star down onto the horizon.

**Euclid**: Euclid of Alexandria was a creek mathematician often reffered to as the father of geometry. he was active in alexandria during the reign of ptolemy 1 (322-283 BC)

**Euclidean Distance**: The distance between the pairs of points in euclidean spaces.

**Pythagorean Theory**: Pythagoras Theorem is a relation in Euclidean Geometry among the three sides of a right triangle. It states, in any right triangle, the area of the square whose side is the hypotonus (the side opposite the right angle) is equal to the sum of the areas of the squares whose sides are the two legs ( The two sides that meet at a right angle).

**Map Algebra**: A simple and elegent set based algebra for manuipulating geographic data, proposed by Dr. Dana Tomlin in the early 1980’s.

It is a set of primitive opperations in a GIS which allows two or more raster layers of similar dimensions to produce a new raster layer (map) using algabraic opperations such as addition, subtraction, etc.

**Spatial Analysts key functions**:

- Perform overlay analysis including Union, Intersect, and Erase.
- Perform proximity analysis including Buffer, Near, and Point Distance.
- Perform surface analysis including Aspect, Hillshade, and Slope.
- Perform raster processing and conversion.

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