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Outline The Engineer’s Transit and Theodolite Lecture 6 GE10: General Surveying I
Department of Geodetic Engineering University of the Philippines, Diliman
Engineer’s Transit Credited ed Credit
to Roemer, Roemer, a Dani Danish sh Astr Astron onom omer er, who who in 1690 1690 used used the the inst instru rume ment nt to obse observ rve e the the pass passag age e (tra (trans nsit it)) of star stars s acro across ss the the cele celest stia iall meridian
Essentially
I. Engine Engineer’ er’s s Transi ransitt I. Main Main Parts rts I . Upper Pl Pla te te II. Lowe Lowerr Plate Plate III. Leveling Leveling Head Assembly Assembly II. Setting Setting up the the transi transitt III. Leveling Leveling of the Transit Transit IV. Care of of the Transit Transit II. Theo Theodo dolit lite e I. Types ypes of Theo Theodo dolit lite e I. Repe Repeat atin ing g The Theod odoli olite te II. Directio Directional nal Theod Theodolit olite e III. Digital Theodolite Theodolite II. II. Main Main Par Parts ts III. Setting up up the theodolite theodolite
Main Parts 1. Upper Plate (or (or Alidade) 2. Lower Lower Plate 3. Leveling Head Head Assembly
a telescope and two large protractors
1
protractor mounted in the horizontal plane and the other in a vertical plane
An
instrument of precision
Main Pa Parts of of th the En Engineer’s Tr Transit
Parts of of th the En Engineer’s Tr Transit
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I. Upper Plate Consists
of the entire top of the
transit Entire assembly rotates about a vertical axis Contains the ff: vertical
circle and vernier supports the telescope and level tube compass box circular cover plate and plate level vials upper clamp tangent screw needle lifter
I. Upper Plate 1. TELESCOPE Used
Can be rotated about its horizontal axis
Direct position => level vial is above the telescope Reversed position => level vial is below the telescope
standards:
for: 1. Fixing the direction of LOS 2. Viewing the objects 3. Magnification in the FOV
I. Upper Plate
I. Upper Plate
2. STANDARDS
3. COMPASS BOX
Integral parts of the upper plate Used to: 1. Hold into position the horizontal axle level 2. Elevate or depress the telescope by rotating on an axis perpendicular to the
Used to: 1. Establish magnetic meridian 2. Allow rough checks on measured angles Magnetic needle can be lifted from its pivot by the needle lifter
LOS
I. Upper Plate 4. PLATE LEVEL VIALS Positioned at right angles to each other
I. Upper Plate 5. VERTICAL CIRCLE Attached Used
to the telescope and rotates with it to measure vertical angles
Used
to establish the upper and lower plates in a horizontal plane
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I. Upper Plate 6. PLATE VERNIERS Two opposite verniers (A & B) A vernier is adjacent to the eyepiece where it is easily u sed B vernier is 180o from A vernier
I. Upper Plate
I. Upper Plate 7. TELESCOPE CLAMP Tightened
to hold the telescope horizontal or at any desired inclination Located near the horizontal axle of the transit
I. Upper Plate
8.TELESCOPE TANGENT SCREW
9. UPPER CLAMP
a.k.a. vertical circle tangent screw
Enables the telescope to be rotated in small movements about the horizontal axis when the telescope clamp is tightened Useful when setting the cross hairs precisely on a distant point sighted
I. Upper Plate 10. OPTICAL PLUMMET
Small telescope thru the vertical center of the transit Enables the instrument to be centered over a given point quickly and precisely by means of an optical system
A locking device When tightened, it causes the upper and lower plates to lock together Most have round heads and usually turn in the direction tangent to the motion they control
II. Lower Plate Or horizontal circle Where horizontal angles are measured Graduated on its upper face and divided around its circumference into 360 o and further subdivisions Can be held stationary while the upper plate is rotated or can be rotated independently As one unit, can be rotated also with the upper plate The underside is attached to a vertical and tapering spindle called the outer spindle
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II. Lower Plate 1. LOWER CLAMP
Attached to the horizontal circle Does not rotate with the horizontal circle Used to control the rotation of the horizontal circle Stops any motion between the leveling head and the lower plate
III. Leveling Head Assembly Lower part of the transit Allows the transit to be leveled and centered over a point Consists of:
1. 2. 3. 4.
bottom horizontal foot plate 4 leveling screws plumb bob chain a device that permits small lateral movements of transit
II. Lower Plate 2. LOWER TANGENT SCREW Used to make precise settings after the lower clamp is tightened It moves the lower plate to a desired exact position using a small range of movement
III. Leveling Head Assembly 1. LEVELING SCREWS
Used for leveling the instrument by the plate levels Operate in pairs and always turned in opposite directions Screws are loosened when desired to shift transit laterally with respect to the foot plate
III. Leveling Head Assembly 2. PLUMB BOB CHAIN Chain with a hook: Suspended from the bottom part of the leveling head assembly Hangs between the tripod legs
Used for attaching a string an a plumb bob so that the instrument may be set exactly over the selected point on the ground Plumb bob string always hang vertical due to gravity
SETTING UP THE TRANSIT
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1. POSITIONING THE TRIPOD
2. MOUNTING THE TRIPOD
1. On fairly level ground:
tripod is set up near and over the selected point with the legs well spread apart to ensure stability see to it that the tripod head is nearly stable
2. On hillsides or along a slope:
1 of its legs should extend uphill and the 2 downhill each tripod leg is then moved as required to make the tripod head nearly level
3. Set the tripod in a convenient height (no need to stretch or stoop)
3. ATTACHING THE PLUMB BOB Plumb bob and a string is attached to the transit by suspending it from the hook and chain that hangs at the bottom of the leveling head. Raise or lower the plumb bob using the sliding loopknot Lower down the plumb bob within about 0.5 cm above the ground point Bring the plumb bob close to the center of the point by moving or pressing 1 or 2 tripod legs more firmly into the ground
1. Remove the transit from its carrying case by grasping it with both hands at the leveling head assembly or at the upright standards 2. With one hand, screw the leveling head of the transit and firmly onto the tripod head while holding the standards at the other hand 3. The transit should fit snugly and bear firmly. 4. Remove the objective cap and replace with the sunshade
4. FINAL CENTERING
See to it that the wing nuts of the tripod is tightened Shift the leveling head of the transit along the foot plate to exactly center the plumb bob Use the optical plummet if available for accurate centering: look at the optical plummet shift the instrument until the reticle is precisely centered on the ground point
LEVELING THE PLATE LEVEL BUBBLE
LEVELING OF THE TRANSIT
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LEVELING THE PLATE LEVEL BUBBLE 1. The bubble is centered by rotating screws 1 and 2 in opposite directions the rotations (see figure) will cause the bubble to move from left to right 2. Next, rotate the instrument so that the one end of the bubble tube is aligned with the remaining screw 3. Center the bubble in this position by rotating this remaining screw 4. The rotation indicated in the figure will cause the bubble to move away from level screw 3
LEVELING THE PLATE LEVEL BUBBLE 5. Return to the original position and check centering of the bubble. 6. Rotate through 180 o so that end A of the bubble tube is on line with level screw . 7. Repeat the previous steps so that all bubble tubes are leveled in every direction.
CARE OF THE TRANSIT
CARE OF THE TRANSIT
1. Store the transit in its carrying case when not in use 2. Remove the transit from the tripod and carry it in its box when transporting in a vehicle or over a long walking distance 3. If it becomes went or damp, dry it off with absorbent cloth or preferably in sunlight 4. The objective lens should not be wiped as it is easily scratched
CARE OF THE TRANSIT 5. Protect the instrument at all times from any shock or sudden jolt
never allow the instrument to fall or drop
6. Hold the transit in the arms with the tripod sticking out to the side or behind NOT on the shoulder do this when: 1. Carrying it inside a building 2. There is danger of striking the instrument against any obstructions
clean it by rubbing gently with a piece of soft cloth moistened in alcohol or with a piece of lens paper finish off with a camel’s hair brush
CARE OF THE TRANSIT 7. The transit should be lifted from the carrying case by grasping the standards and NOT by the telescope. 8. Tripod legs should be spread apart to make it stable. 9. Tripod shoes should be sunk firmly to the ground. 10.It should never be left unattended because it may be upset by passing vehicles, stray animals, playing children, wind or maybe stolen. 11.Avoid setting the transit on concrete slabs, boulders, and steel plates
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CARE OF THE TRANSIT 12.Graduated circles and verniers should not be touched with the fingers. This will tarnish their surfaces. 13.Tarnished surfaces should are cleaned by applying a thin film of oil which is left for a few hours and then wiped off with a soft clean rag. 14.Tighten clamps in a definite and firm manner, not too severe. 15.A waterproof cover for the transit should always be brought along in case of rains, showers and thunderstorms.
MAIN SCALE AND VERNIER
READING TRANSIT VERNIERS
MAIN SCALE AND VERNIER LEAST COUNT Fineness of reading of the vernier and main scale Determine by dividing the length of the smallest division on the main scale by the total number of vernier divisions.
LC
s =
n where: LC = Least Count s = value of the smallest division on the main scale n = no. of divisions on the vernier
MAIN SCALE AND VERNIER LEAST COUNT (Example)
READING TRANSIT VERNIERS
A horizontal or vertical angle is read by finding the graduation on the vernier scale which coincides with a graduation on the main (circle) scale used In case of double vernier, there will always be 2 coincident line 1 for a CW angle & the other for a CCW angle The index mark of the vernier will show the number of degrees or fractional part of a degree (usually in multiples of 30, 20, 15 or 10 min) passed over on the main scale Additional fractional parts of a degree (to be added to the main scale reading) are to be determined from the coincident graduation on the vernier
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READING TRANSIT VERNIERS
Theodolite The name given to the earliest version of a
s = 30 min
n = 30
LC = 30 min/30 LC = 1 min Readings: CW:
178o30’+12’
Check:
=
178o42’
device to measure angles in the horizontal and vertical planes, designed and built in England in about 1725. Theodolite in the 1800’s were not capable of the ability to be transited or turned 180 0 about its horizontal axis, although this capability was included in an instrument called transiting theodolite. In Europe, the name theodolite was retained; in the United States the term transit was kept.
178o42’+ 181o18’ = 360o
CCW: 181o00’+18’ = 181o18’
Types of Theodolite 1. Repeating Theodolite 2. Directional Theodolite 3. Digital Theodolite
Types of Theodolite 1. Repeating Theodolite: can measure a horizontal angle as many times as required by adding them successively on the graduated circle capable of accumulating angles on its horizontal circle by means of its upper and lower motions horizontal scales may allow horizontal angles to be read directly to 10 sec or 20 sec.
Types of Theodolite
Types of Theodolite
2. Directional Theodolite:
3. Digital Theodolite:
Horizontal circle remains fixed during a series of observations Telescope is sighted on each of the points and directions rather than angles to these points are read on the circle Required horizontal angle is determined by calculating the difference of two observed directions A reading on a directional theodolite represents the mean of two diametrically opposed sides of the circle. It is equivalent to averaging the readings of the A and B verniers of a transit.
Resembles very closely a standard theodolite since horizontal and vertical angles in a survey are measured in a simi lar manner.
It can be combined with an EDM instrument and microcomputer to assemble into what is called a total station instrument or an electronic tachoemeter.
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Parts of a Theodolite
Parts of a Theodolite
Parts of a Theodolite
Parts of a Theodolite Reading Microscope
Adjustable mirror to illuminate vertical circle Adjustable mirror to illuminate vertical circle Clamping screw for vertical circle
Vertical circle tangent screw
Clamping screw for vertical circle Inverter knob
Vertical circle tangen t screw
Horizontal Tangent Screw
Horizontal Clamp Horizontal Clamp
Parts of a Theodolite (Wild T2)
Horizontal Circle Reading (Wild Theodolite, T2)
Reading: = 94010’ + 02’44.4” = 94012’44.4” where 0.4” is estimated
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Horizontal Circle Reading (Wild Theodolite, T2)
References: Davis, R.E., et. al (1981). Surveying: Theory and Practice. USA: McGraw-Hill, Inc. La Putt, J.P. (2007). Elementary Surveying. Philippines: National Book Store.
THANK YOU
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