# 5 3 coordinate system

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Ngày đăng: 10/07/2018, 12:07

Coordinate Systems and Definitions At the end of this lecture, YOU will be able to; 1.Name the most common map projection model and state the main error introduced by the model Demonstrate the correct use of Latitude, Longitude and depth datum to define positions on Earth’s surface and within the crust 3.State the differences between the different North’s and correct magnetic readings to True North Describe what is meant by “ellipse of uncertainty” and “travelling cylinder” Convert positions between Absolute and relative coordinates COPYRIGHT © 2001, All Rights Reserved Geographic Coordinates  Cartography - Provides a map that gives a mathematical definition for a point on a curved surface and defines it by longitude and latitude  Longitude – Series of lines ALL intersection at the north & south poles From the Prime Meridian, deg – 180 deg to the east is (+) & deg – 180 deg to the west is (-)  Latitude – Equally spaced circles around the earth running east & west Each line is a degree with deg being the equator & 90 deg at each north & south pole  References – The starting point for Longitude is the Prime Meridian & for Latitude is the Equator COPYRIGHT © 2001, All Rights Reserved Universal Transverse Mercator (UTM) System COPYRIGHT © 2001, All Rights Reserved Rectangular Grid System – UTM (Universal Transverse Mercator) COPYRIGHT © 2001, All Rights Reserved Sector Origins for UTM System COPYRIGHT © 2001, All Rights Reserved Azimuth Reference Systems True North – is meridian North Magnetic North - is compass North Grid North – is UTM North COPYRIGHT © 2001, All Rights Reserved Magnetic Declination  The declination is the angle between True North and local magnetic North measured positively eastward – Easterly declination (clockwise) is positive – Westerly declination (anti-clockwise) is negative  TN MN EAST Declination is added to Magnetic Azimuth TRUE NORTH MAGNETIC NORTH X X COPYRIGHT © 2001, All Rights Reserved Grid convergence  Grid convergence is the amount of distortion for each mapping area GN TN LONGITUDINAL UTM ZONE COPYRIGHT © 2001, All Rights Reserved Convergence correction  The convergence is the angle between True North and Lambert or UTM North (Grid North) as measured from True North TN GN – Easterly Convergence (clockwise) is positive – Westerly Convergence (anti-clockwise) is negative  Convergence is SUBTRACTED from Corrected Azimuth COPYRIGHT © 2001, EAST All Rights Reserved Total Azimuth Correction TN = True North MN = Magnetic North GN = Grid North C = Grid Convergence D= Magnetic Declination correction ∠1 = Magnetic Azimuth ∠2 = True Azimuth = Magnetic Azimuth + Magnetic Declination ∠3 = Grid Azimuth = True Azimuth - Grid Convergence ∠3 = Grid Azimuth = Mag Azimuth + Magn Declination - Grid Convergence All azimuths and corrections are positive in a clockwise direction COPYRIGHT © 2001, All Rights Reserved Total Azimuth Correction TN MA MN -10° GN +6° EXAMPLE: • Magnetic Declination = - 4° • Grid Convergence = -10° -4° • Tot Correction.=(- 4°) - (-10°) = 6° • Add 6° Total Correction to each magnetic survey Total correction = Magnetic Declination - Grid Convergence Corrected (Grid) Azimuth = Magnetic Azimuth + Total Correction COPYRIGHT © 2001, All Rights Reserved Relative Coordinates Absolute coordinates Surface Location X Y Z Eastings Northings Depth Target Location 262744 6354300 120 Surface Location 262544 6355500 -2130 Target Location 0 200 -1200 2250 N Surface Location X-262744 ; Y-6354300 Relative coordinates W Surface Location E X-0 ; Y-0 Target Location Target Location X-262544 ; Y-6355500 X-200 ; Y 1200 S COPYRIGHT © 2001, All Rights Reserved Anti-collision plots COPYRIGHT © 2001, All Rights Reserved Traveling cylinder COPYRIGHT © 2001, All Rights Reserved Ellipse of Uncertainty  The systems for surveying directional wells have limited accuracy  The survey may also be subject to errors resulting from downhole changes in the magnetic field, or magnetic interference  The ellipse represents the various position of a given well survey point based on the error associated with the components of a survey measurement COPYRIGHT © 2001, All Rights Reserved Coordinate Systems and Now , YOU should be able to; Definitions 1.Name the most common map projection model and state the main error introduced by the model Demonstrate the correct use of Latitude, Longitude and depth datum to define positions on Earth’s surface and within the crust 3.State the differences between the different North’s and correct magnetic readings to True North Describe what is meant by “ellipse of uncertainty” and “travelling cylinder” Convert positions between Absolute and relative coordinates COPYRIGHT © 2001, All Rights Reserved Any questions before the test? This is a closed book test Please put away your notes and handouts now COPYRIGHT © 2001, All Rights Reserved ... Mercator (UTM) System COPYRIGHT © 2001, All Rights Reserved Rectangular Grid System – UTM (Universal Transverse Mercator) COPYRIGHT © 2001, All Rights Reserved Sector Origins for UTM System COPYRIGHT... = Magnetic Azimuth + Total Correction COPYRIGHT © 2001, All Rights Reserved Relative Coordinates Absolute coordinates Surface Location X Y Z Eastings Northings Depth Target Location 262744 6354300... associated with the components of a survey measurement COPYRIGHT © 2001, All Rights Reserved Coordinate Systems and Now , YOU should be able to; Definitions 1.Name the most common map projection
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