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.
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.

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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 &
for Latitude is the Equator.
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Universal Transverse Mercator
(UTM) System

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Rectangular Grid System –
UTM (Universal Transverse

Mercator)

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Sector Origins for UTM
System

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Azimuth Reference
Systems

True North – is meridian North

Magnetic North - is compass North

Grid North – is UTM North

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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

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Grid convergence

 Grid convergence is the
amount of distortion for
each mapping area.
GN TN

LONGITUDINAL
UTM ZONE
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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

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EAST

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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
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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
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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
0
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
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Anti-collision plots

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Traveling cylinder

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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.
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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.
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.

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Any questions before
the test?
This is a closed book test. Please put
away your notes and handouts now.

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