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

[email protected]



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.



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

4

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



Earth, datum, Projections, Maps and Coordinate systemsEarth, datum, Projections, Maps and Coordinate systems

5



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

6

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)



11.. FlatFlat earthearth modelsmodels

22.. SphericalSpherical earthearth modelsmodels

33.. EllipsoidalEllipsoidal earthearth modelsmodels

Earth Shape ModelsEarth Shape Models

7

Flat earth Flat earth

Spherical Earth Spherical Earth Ellipsoidal Earth Ellipsoidal Earth



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

8

Earth Centered X/Y/Z Geodetic Lat/Lon/Height Global Cartesian Global Cartesian Geographical coordinate Geographical coordinate



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)



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)



Basics of Map ProjectionsBasics of Map Projections11

http://earth.rice.edu/mtpe/geo/geosphere/topics/mapprojections.html



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



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

.



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



15



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.



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.



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



The gravity controlled gyro obtained by pendulum


Fig. Behaviour of the gravity-controlled gyro (undamped).




Fig. Behaviour of the gravity-controlled gyro (damped).



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

21

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



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



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



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.



Questions….Questions….

25

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.

CONTROL SURVEY- Gyrotheodolite By D.M Siddique

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