13.Theodolite
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Transcript of 13.Theodolite
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Contents• Introduction to Surveying
• Setting and Leveling of Theodolite and Tilting Levels and parts of these instruments
• Measurement of Vertical Angle using Theodolite
• Measurement of Elevation between two points using Tilting Level
• Measurement of distance
• Measurement of area using Chain Surveying
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Introduction to Surveying
Planning and DevelopmentBuilding Surveying
Quantity Surveying Mineral Surveying
Geodetic Surveying
Topographical Surveying
Hydrographic Surveying
Engineering Surveying
Land Surveying
Land Surveying
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Engineering Surveying is used to
at the concept and design stage
Production of maps or plans
at the construction stage
Setting out and measurement
at the post construction stage
Measurement and monitoring
Surveying for all three aspects involves the measurement of three parameters :
Horizontal Distances Vertical Distances Angles
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Horizontal Distances by:
Taping & Chaining Optical Methods Electronic Methods
Vertical Distances by
Taping Optical Methods Electronic Methods
Angles by:
Magnetic Compass Sextant Theodolite
A variety of methods and equipment can be used to measureeach of these parameters.
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A
P
B
HorizontalAngle
Vertical Angle
Vertical Angle
(Elevation +ve)
(Depression -ve)
Measurement of Angles
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A
P
B
HorizontalAngle Vertical Angle
Vertical Angle
I
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Vertical Angle
A
P
B
I
Vertical Angle
Horizontal anglesare the same
ButVertical anglesvary withelevation (height)of instrument
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THEODOLITE
(For Measuring Angles)
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Setting up a TheodoliteEnsure that :-
• the tripod head is approximately level
• the tripod feet are firmly fixed in the ground
This should be done BEFORE removing the theodolite from its box.
Tripod Feet
Tripod Head
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Tripod Height -middle toupperchest height
Tripod Head Horizontal
Feet - Duginto ground(if possible)
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Setting up a Theodolite Place the theodolite on top of the tripod, and tighten the centring screw to clamp the theodolite centrally on the tripod head.
Hold Theodoliteby handle
Attach to tripodhead
Do not let goof handleuntil theodoliteis attached totripod.
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TribrachLevellingScreworFoot Screw
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Pond Bubble
Plate Bubble
Forapproximatelevelling
Foraccuratelevelling
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Standing axis
Trunnionaxis
CollimationAxis
EyepieceFocus(For cross hairs)
InternalFocus(For sightingobject)
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Levelling up a Theodolite
Carry out an approximate levelling. Using the pond bubble and by adjusting the length of TWO tripod LEGS, bring the pond bubble into the centre of the pond bubble tube.
The theodolite is ROUGHLY LEVELLED AND CENTERED over the station.
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Setting up a Theodolite
Fine level the theodolite using the PLATE level bubble tube and foot SCREWS
Bubble follows LEFT THUMB
Position aPosition a
Position a) align the plate level bubble tube with two foot screws.
Centre the bubble by rotating the two foot screws in opposite directions. The bubble follows the LEFT thumb.
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Plate Level Bubble Tube
Foot Screws
Required to move the bubble to the right
Bubble follows direction of left thumb
Both thumbs move in (or out)
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Position a
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• Position b) align the plate level bubble tube with the third foot screw. i.e. 900 from position a)
Centre the bubble by rotating the third foot screw (only)The bubble follows the LEFT thumb.
Using the thirdfootscrew only
Levelling up a Theodolite
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Position b900 to position a
Bubble still follows LEFT THUMB
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Position b900 to position a
Bubble still follows LEFT THUMB
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Position b900 to position a
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Position a
Repeat position a and b
Position b900 to position a
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Vertical Circle - (for vertical angles)
Face LeftF/L
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Transit Telescope
Rotate Theodolite
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Face Right(F/R)
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Some Typical Theodolite Diaphragms
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This is FACE LEFT This is FACE RIGHT
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Target
We need to superimpose the theodolite diaphragm over the target
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This is how we should sight a target for
horizontal angle measurements.
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This is how we should sight a target for
vertical angle measurements.
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Example:
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Theodolite - Instrument Errors
Plate Bubble Error . This is checked every time the theodolite is set up.
Non - Vertical Cross Hairs . Move the telescope up and down while sighting a well defined distant point.
Horizontal Collimation Error . Sight a well defined point and read the horizontal circle on F/L and F/R. The difference should be <40”
Vertical Collimation Error . Sight a well defined point and read the vertical circle on F/L and F/R. The difference should be <40”
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Exp: 14 Measurement of Height of an Object, of which base is not accessible
OBSERVATIONS:
Bench Mark:Height of Instrument at First station (A) w.r.t. Bench Mark (x) = Height of Instrument at Second station (B) w.r.t. Bench Mark (y) = Horizontal distance between the two instrument stations (b) = Difference in the height of instrument at first and second stations (s) =
Instrument Station
Face Vertical Angle Reading Angle Remarks
Vernier C 0 ‘ ‘’
Vernier D0 ‘ ‘’
Mean 0 ‘ ‘’
A Left/Right
B Left/Right