Positioning POSITIONING AND COORDINATE SYSTEM The by IbrahimMassaad

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									    POSITIONING AND
   COORDINATE SYSTEM
The earth is an oblate spheroid
(a squashed sphere) and maps
are flat, which makes it difficult
         to map the earth


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                Positioning

    The earth is
    divided into
    latitude and
    longitude
    The equator is 0
     degrees latitude
     and poles are 90
     degrees
    The length of a
     degree of latitude
     is always the
     same
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              Positioning
    Meridians or lines of longitude run
     from pole to pole
    The equator is divided up into 360
     degrees
    The distance between meridians
     changes depending upon the latitude
    The prime meridian runs thru the
     observatory at Greenwich, England
    Longitude 0 to 180 degrees east and
     west from that point
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              Positioning
    Calculating the longitude and
    latitude of a well on a map can
    be very complicated
    Rectangular grids have been
    developed for use in surveying
    A geodetic datum is a definition
    of a model for the surface of the
    earth

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               Positioning
    An ellipsoid consist of:
    A definition of an ellipsoid
    A definition of how the ellipsoid is
     oriented to the earth’s surface
    A definition of the units of length
    An official name
    Region(s) of the earth’s surface for
     which the datum is intended to be
     used

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             Positioning
    The NAD27 or North American
    Datum 1927 is the most
    commonly used datum for North
    America
    ED50 or European Datum 1950 is
    the most commonly used datum
    in the North Sea



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              Positioning
    A map projection is a
    mathematical formula which has
    been designed to convert the
    latitude/longitude method of
    positioning to a flat map
    With a flat map, wellbores can be
    spotted with an X Y coordinate
    system

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             Positioning
    The most commonly used map
    projection is the Universal
    Transverse Mercator (UTM)
    The Lambert map projection is
    also common throughout the
    world and is the most common
    in the USA



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             UTM System
    On most maps, the lines of
    latitude and longitude are curved
    The quadrangles formed by the
    intersections of these lines are
    of different sizes and shapes,
    which complicates the locations
    of points and the measurement
    of directions

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              UTM System
     The UTM system tries to solve
     this problem
     The world is divided up into 60
     equal zones, each 6 degrees
     wide
     The zones are from 84.5 degrees
     North to 80.5 degrees south
     Polar regions are covered by
     other, special projections
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     UTM System

                                       Each zone has
                                       its own origin at
                                       the intersection
                                       of its central
                                       meridian and the
                                       equator
                                       The zone is
                                       flattened and a
                                       square imposed
                                       on it

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                UTM System

     The outer edges
     for the grid are
     curved
     The convergence
     is the difference
     between grid north
     and true north
     At the central
     meridian, grid
     north = true north

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              UTM System
     Each of the 60 zones are
     numbered starting with one at
     the 180th meridian
     The areas east and west of the
     Greenwich Meridian are covered
     by zones 30 and 31, respectively




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              UTM System
     Points on the earth may be
     identified by its zone number, its
     distance in meters from the
     equator (northing) and its
     distance in meters from a north-
     south reference line (easting)




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              UTM System
     To avoid negative values of
     eastings, the central meridian in
     any zone is assigned the
     arbitrary eastings value of
     500,000 m
     Along the equator a zone is
     about 600,000 m wide, tapering
     towards the polar regions
     Eastings range in values from
     approximately 200,000 to 800,000
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     UTM System




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               UTM System
     For points north of the equator,
     northings are measured directly
     in meters, with a value of zero at
     the equator and increasing
     toward the north




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              UTM System
     To avoid negative numbers in
     the Southern Hemisphere, the
     equator is assigned a value of
     10,000,000 m and displacements
     in the south are measured with
     decreasing, but positive, values




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              UTM System
     The well proposal is usually
     derived from coordinates on a
     grid system and therefore
     directions will be referenced to
     grid north
     Directional surveys reference
     true north
     It may be necessary to convert
     from one to another
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     Lambert System

                                         The Lambert
                                         Conformal Conic
                                         Projection was
                                         introduced by
                                         Johann Lambert
                                         in 1772
                                         It is also called
                                         the Conical
                                         Orthomorphic
                                         projection
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            Lambert System
     Meridians are equally spaced
     straight lines converging at one
     of the poles
     Parallels are unequally spaced
     concentric circular arcs centered
     on the pole of convergence
     The cone is considered as
     penetrating the earth along one
     standard parallel and emerging
     along another
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             Lambert System

     The distance scale that applies to the
     whole map is exact only at the
     standard parallels




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            Lambert System
     When used for maps of the
     United States and individual
     states, the standard parallels are
        o        o
     33 and 45 North
     The Lambert Conformal Conic
     Projection was adopted as the
     official projection for the SPCS
     (State Plain Coordinate System)
     for states of predominantly east-
     west expanse
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             Lambert System
     A Transverse Mercator system was
     used for states predominantly north-
     south expanse
     The state plane coordinate system is
     the legal system used to survey on
     land SPCS 27 and SPCS 83
     The public land survey system is a
     grid system used on land to locate
     places on the earth


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             Public Land Survey
     The most common
     is the township
     and range system
     A principal meridian
      and base line was
      established
     Supplementary
      survey lines were
      spaced at 24 miles
     The 24 mile squares
      were subdivided into
      6 mile squares

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           Public Land Survey
     The 6 mile squares are townships
      going north and south and ranges
      going east and west (in some places
      a township is called a tier)
     The township and ranges are divided
      into sections
     There are 36 sections to a township
      and range
     Section can be further broken down
      into parts of a section
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     Public Land Survey

                                                       The public
                                                       land survey
                                                       system is not
                                                       extremely
                                                       accurate and
                                                       there are
                                                       differences
                                                       between true
                                                       north and
                                                       section lines
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           Public Land Survey
     The survey data may be less
     accurate than the land survey
     and is +/- 0.5o azimuth at best




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           Public Land Survey
     The original 13 states and some
     states in the southwest (Texas) do
     not use the township and range
     system
     They use the metes and bounds
     system
     In this method, lines are surveyed
     along the irregular edges of the
     property and the azimuth and lengths
     of the lines recorded
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           Public Land Survey

     There are no
     references to a
     national or
     international
     measurement
     system




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