5 3 coordinate system

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.. Demons

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.

2 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.

4 Describe what is meant by “ellipse of uncertainty” and “travelling cylinder”.

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, 0 deg – 180 deg to the east is (+) & 0 deg – 180 deg to the west is (-)

 Latitude – Equally spaced circles

around the earth running east & west Each line is a degree with 0 deg

being the equator & 90 deg at each north & south pole

 References – The starting point for

Longitude is the Prime Meridian &

Universal Transverse Mercator (UTM) System

Rectangular Grid System –

UTM (Universal Transverse

Mercator)

Sector Origins for UTM

System

Azimuth Reference

Systems

True North – is meridian North Magnetic North - is compass North Grid North – is UTM North

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

TRUE NORTH

MAGNETIC NORTH

X

X

Grid convergence

 Grid convergence is the amount of distortion for

each mapping area.

GN TN

LONGITUDINAL

UTM ZONE

Convergence correction

 The convergence is the angle between True North

and Lambert or UTM North (Grid North) as

measured from True North

– Easterly Convergence (clockwise) is positive

– Westerly Convergence (anti-clockwise) is negative

 Convergence is SUBTRACTED from Corrected

Azimuth

TN

GN

EAST

Total Azimuth Correction

∠ 2 = True Azimuth = Magnetic Azimuth + Magnetic Declination

∠ 3 = Grid Azimuth = True Azimuth - Grid Convergence

∠ 3 = Grid Azimuth = Mag Azimuth + Magn Declination - Grid Convergence

TN = True North

MN = Magnetic North

GN = Grid North

C = Grid Convergence

D= Magnetic Declination correction

∠1 = Magnetic Azimuth

Total Azimuth Correction

EXAMPLE:

• Magnetic Declination = - 4°

• Grid Convergence = -10°

• Tot Correction.=(- 4°) - (-10°) = 6°

• Add 6° Total Correction to each

magnetic survey

GN

MN

-10°

-4°

+6°

TN

MA

Relative Coordinates

Surface Location

Target Location

Surface Location

Target Location

Y Northings 6354300 6355500 0 -1200

Absolute coordinates Relative coordinates

Surface Location X-262744 ; Y-6354300

Target Location

N

Surface Location X-0 ; Y-0

Target Location

Anti-collision plots

Traveling cylinder

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

Coordinate Systems and

Definitions Now , YOU should be able to;

1.Name the most common map projection model and state the main error

introduced by the model.

2 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.

4 Describe what is meant by “ellipse of uncertainty” and “travelling cylinder”.

5 Convert positions between Absolute and relative coordinates.

Any questions before

the test?

away your notes and handouts now.