Monday, 30 October 2017

DIRECTIONAL DRILLING POSITIONING AND COORDINATES SYSTEMS

Geographic Coordinates (Latitude and Longitude)


Positioning and Coordinate Systems

Ellipsoid

is the name of the volume obtained when an ellipse is rotated about one of
its axes. Specifically, an oblate spheroid is an ellipse rotated about the shorter
(semi-minor) axis.
The Earth is not an exact ellipsoid, and deviations from this shape are continually
evaluated.
the curvature of the Earth's surface is not uniform due to irregularities in the gravity field

Geodetic Datum

is a definition of a model for the surface of the earth. They usually consist of the definition of an ellipsoid, a definition of how the ellipsoid is oriented to the earth's surface, a definition for the unit of length, an official name, and region(s) of the earth's surface for which the datum is intended to be used.

Map Projection

A map projection is a mathematical formula which has been designed to convert the latitude/longitude method of positioning on the surface of a sphere into another method of positioning which can be plotted onto a flat map with some degree of controlled error and known accuracy. ( X Y Cartesian) coordinates.
The most commonly used map projection is
1- the Transverse Mercator (TM) 
2- the Universal Transverse Mercator (UTM) 
3- The Lambert map projection 

Convergence

 is the difference between Grid North and True North (Figure 3-3). Clearly, at the central meridian, Grid North equals True North. Convergence will vary with distance away from the central meridian and with distance away from the equator. Convergence is negative to the East and positive to the West.

Grid north: Is a navigational term referring to the direction northwards along the grid lines of a map projection. It is contrasted with

True north: Is the direction of the North Pole. 

Magnetic north: Is the direction in which a compass needle points.

Lambert Projection:

In cartography, the Lambert cylindrical equal-area projection, or Lambert cylindrical projection, is a cylindrical equal-area projection. This projection is undistorted along the equator, which is its standard parallel, but distortion increases rapidly towards the poles. Like any cylindrical projection, it stretches parallels increasingly away from the equator. The poles accrue infinite distortion, becoming lines instead of points.


Positioning and Coordinate Systems

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