control survey- gyrotheodolite by d.m siddique
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ADVANCE ENGINEERING SURVEYING(3+1)
LECTURE 15: CONTROL SURVEY- Gyrotheodolite
IN TR T RIN TR T R
Date: 06/11/2012
DR. MOHSIN SIDDIQUE
ASSIST. PROFESSOR
DEPARTMENT OF CIVIL ENGINEERING
FAST-NUCES, LAHORE
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Control Surveys: Geodesy, Universal Transverse
Mercator (UTM) and other Map Projections,
Coordinate Systems and Datum, Horizontal controltechniques, Survey markers, Observations on Polaris,
Computation technique for azimuth determination
Overview of Control surveyOverview of Control survey
and Gyro-theodolite.
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Geodesy also named geodetics, a branch of earth sciences, is the
scientific discipline that deals with the measurement and representation
of the Earth, including its gravitational field, in a three-dimensional
time-varying space
Map Projection - the transformation of a curved earth to a flat map
Geodesy, Map Projections and Coordinate systemGeodesy, Map Projections and Coordinate system
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Coordinate systems - Any set of numbers, usually in sets of two or
three, used to determine location relative to other locations in two or
three dimensions
-(x,y,z) coordinate systems for map data
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Earth, datum, Projections, Maps and Coordinate systemsEarth, datum, Projections, Maps and Coordinate systems
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The reference ellipsoid surface (a map of averagesea level).
The reference geoid surface(a mean sea level surface).
Earth Surface: Ellipsoid, Geoid and Topograhic surfaceEarth Surface: Ellipsoid, Geoid and Topograhic surface
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The real surface of the Earth(the ground) also called thetopographic surface.
Models of ellipsoid datum
1. The Clark ellipsoid of 1866 (Clark, 1866)
2. Geodetic reference system of 1980 (GRS80)
3. Word geodetic system of 1984 (WGS84)
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11.. FlatFlat earthearth modelsmodels
22.. SphericalSpherical earthearth modelsmodels
33.. EllipsoidalEllipsoidal earthearth modelsmodels
Earth Shape ModelsEarth Shape Models
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Flat earth Flat earth
Spherical Earth Spherical Earth Ellipsoidal Earth Ellipsoidal Earth
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Types of coordinate systems
(1) Geographic coordinates (φ, λ, z)
(2) Global Cartesian coordinates (x, y, z): A system for the whole earth (3) Projected coordinates (x, y, z) on a local area of the earth’s surface
Coordinate SystemsCoordinate Systems
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Earth Centered X/Y/Z Geodetic Lat/Lon/Height Global Cartesian Global Cartesian Geographical coordinate Geographical coordinate
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A map projection is the systematic transformation of locations on the earth(latitude/longitude) to planar coordinates
The basis for this transformation is the geographic coordinate system (whichreferences a datum)
Map projections are designed for specific purposes
Projected Coordinate SystemsProjected Coordinate Systems
Curved Earth
Geographic coordinates: φ , λ
(Latitude & Longitude)
Flat Map
Cartesian coordinates: x,y
(Easting & Northing)
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A map projection is a mathematical model for conversion of locations from a
three-dimensional earth surface to a two-dimensional map representation. This
conversion necessarily distorts some aspect of the earth's surface, such as
area, shape, distance, or direction.
Earth to globe mapEarth to globe map
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Representative Fraction
Globe distance
Earth distance
=
Map Scale: Map Projection:
Scale Factor
Map distance
Globe distance
=
(e.g. 1:24,000) (e.g. 0.9996)
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Basics of Map ProjectionsBasics of Map Projections11
http://earth.rice.edu/mtpe/geo/geosphere/topics/mapprojections.html
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Traditional methods in horizontal control surveys require observations
of horizontal distances, angles and observations of astronomic
azimuths.
1. Triangulation
Horizontal Control TechniquesHorizontal Control Techniques12
2. Precise Traversing
3. Trilateration
4. Combined networks
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Survey markers, also called survey
marks, and sometimes geodetic
marks, are objects placed to mark
key survey points on the Earth'ssurface. They are used in geodetic
and land surveying.
Survey markersSurvey markers13
Informally, such marks are referredto as benchmarks, although strictly
speaking the term "benchmark" is
reserved for marks that indicate
elevation.
Horizontal position markers used for
triangulation are also known as trig
points ortriangulation stations
.
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Polaris also called north star
has been used for centuries by
sailors navigating in the northern
hemisphere of our globe
PolarisPolaris14
Its very useful because itsapparent path of rotation keeps
the star very close to the
extension of the earth’s pole axis
through north pole
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A gyroscope is a device for
measuring or maintaining
orientation, based on the principlesof angular momentum.
GyroscopeGyroscope16
,
spinning wheel or disk in which theaxle is free to assume any
orientation.
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Although this orientation does not
remain fixed, it changes in response
to an external torque much less and
in a different direction than it wouldwithout the large angular momentum
associated with the disk's high rate
of spin and moment of inertia.
GyroscopeGyroscope17
Since external torque is minimized
by mounting the device in gimbals,
its orientation remains nearly fixed,
regardless of any motion of the
platform on which it is mounted.
A gyroscope in operation with freedom in all three axes. The
rotor will maintain its spin axis direction regardless of the
orientation of the outer frame.
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The gyro spin axis can be made
meridian seeking (maintaining the
spin axis parallel to the earth’s spin
axis) by the use of a pendulumacting under the influence of earth
gravity.
The pendulum causes a force to act
North seeking gyroNorth seeking gyro
upon the gyro assembly that willprecess under its influence.
Precession enables the instrument to
become north seeking.Precession on a gyroscope
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The gravity controlled gyro obtained by pendulum
North seeking gyroNorth seeking gyro
Fig. Behaviour of the gravity-controlled gyro (undamped).
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North seeking gyroNorth seeking gyro
Fig. Behaviour of the gravity-controlled gyro (damped).
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Applications of gyroscopes include
inertial navigation systems where
magnetic compasses would not work
or would not be precise enough, or for the stabilization of flying
vehicles like radio-controlled
helicopters or unmanned aerial
Applications of GyroscopeApplications of Gyroscope
Examples of Gyroscope in consumer
electronics include HTC Titan,Nexus
S,iPhone 4, Nokia 808 PureView,
PlayStation 3 controller, Wii Remote,
etc. Futuristic electronic gyroscopes, or
Control Moment Gyroscope to
ensure Lit Motors C-1 remains
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vehicles. Due to their precision, gyroscopes
are also used to maintain direction
in tunnel mining
In addition to being used incompasses, aircraft, computer
pointing devices, etc., gyroscopes
have been introduced into consumer
electronics.
upright
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A gyro-theodolite is a surveying
instrument composed of a
gyroscope mounted to a theodolite.
It is used to determine the
orientation of true north by locating
the meridian direction.
GyroGyro--theodolitetheodolite22
It is the main instrument for
orientation in mine surveying and in
tunnel engineering, where
astronomical star sights are notvisible.
Gyro-theodolite
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A gyrocompass is a type of non-magnetic
compass which is based on a fast-spinning
disc and rotation of the Earth to
automatically find geographical direction.
Although one important component of a
rocom ass is a rosco e these are not
GyroGyro--compasscompass23
the same devices; a gyrocompass is built touse the effect of gyroscopic precession
Gyrocompass
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Gyrocompasses are widely used for navigation on ships, because they have
two significant advantages over magnetic compasses
they find true north as determined by Earth's rotation, which is different from,and navigationally more useful than, magnetic north, and
GyroGyro--compasscompass24
they are unaffected by ferromagnetic materials, such as ship's steel hull, which
change the magnetic field.
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Questions….Questions….
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Thank you !Thank you !
I am greatly thankful to all the information sources oninternet that I accessed and utilized for the
preparation of present lecture.