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ASSIGNMENT Two | MAY 17 TH 2015 NADIM EL HINDI 20082422 ARP554 | Surveying & Field Surveying | Elias Abi Rizk SPRING 2015 | FAAD | NOTRE DAME UNIVERSITY Surveying and Field Surveying

Surveying and Field Surveying

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  • ASSIGNMENT Two | MAY 17TH 2015

    NADIM EL HINDI 20082422 ARP554 | Surveying & Field Surveying | Elias Abi Rizk

    SPRING 2015 | FAAD | NOTRE DAME UNIVERSITY

    Surveying and Field Surveying

  • Field Surveying

    1

    Leveling: Aims Of This Report

    Aims of this Report:

    -Heights, datums and bench marks

    -Levelling equipment

    -Field procedure for levelling

    -Calculating reduced levels

    -Sources of error in levelling

    -Other levelling methods

    Levelling how heights are defined: - Engineering surveying involves the measurement

    of three quantities; heights, angles and distances. - Levelling is the process of measuring heights. - It is possible when levelling to measure heights with an accuracy of millimeters - Heights can also be measured using total stations, handheld lasers and GPS devices. - However, levelling offers an inexpensive,

    simple and accurate method for measuring

    heights, and it is widely used in

    construction sites. - Any method of measuring the heights of

    points above or below the ground using

    an agreed datum. - These reference points are present in all

    construction sites and has an arbitrary height

    assigned to the point. Most construction sites

    will have several of these benchmarks, and if

    they have heights based on an arbitrary datum,

    they are known as Temporary Bench Marks.

    Figure: Some of the leveling equipments

    Figure: Reading the height

    Figure: How heights are defined

  • Field Surveying

    2

    Heights:

    Heights are defined using horizontal and vertical lines. The

    figure beside shows a plumb-bob suspended at point P, the

    direction of gravity along the plumb-line defines the

    vertical at point P. A horizontal or level line is any line at

    right angles to this point.

    For site work, any horizontal line can be chosen as

    a datum for heights and for levelling. The height of

    a point is measured along the vertical above or

    below the chosen datum. The height of a point

    relative to a datum is known as its reduced level

    (RL).

    Curved Surfaces:

    Level (or horizontal) lines are always at right angles to the

    direction of gravity. The direction of gravity is generally towards

    the center of the earth. Over large areas, as the Earth is curved,

    level surfaces will also be curved. For these, a height difference

    is measured along a vertical between two curved level surfaces.

    Leveling Ruler:

    Levelling involves measuring vertical distances with reference to

    a horizontal plane or surface. To do this, a levelling ruler is

    needed to measure vertical distances and an instrument known

    as a level machine that is required to define the horizontal

    plane.

    Many types of Leveling rulers are used with varying lengths and

    different markings. The E-type face is commonly used in the UK

    and Ireland. This can be read directly to 0.01m and by

    estimation to the nearest mm. The ruler must be held vertically

    a circular bubble is fitted to help with this.

    Figure: Plumb bob suspended to define the vertical line

    Figure: leveling in Curved Surfaces

    Figure: Leveling Ruler and Level Machine

  • Field Surveying

    3

    Level Machine Details:

    1. Focusing screw

    2. Eyepiece

    3. Foot screw

    4. Horizontal circle

    5. Base plate

    6. Tangent screw

    7. Circular bubble

    8. Collimator (sight)

    9. Object lens

    The Main Features of the Telescope:

    1.Object lens

    2.Focusing screw

    3.Focusing lens

    4.Diaphragm

    5.Eyepiece

    The object lens, focusing lens, diaphragm and eye piece are all

    mounted on an optical axis called the line of collimation or the

    line of sight.

    This is an imaginary line which joins the optical center of the

    object lens to the center of the cross hairs.

    When looking through the eye piece of the surveying telescope,

    a set of lines called the cross hairs can be seen. These are used

    for taking measurements from the staff. These cross hairs are

    etched on a small sheet of glass known as the diaphragm.

    To make the telescope work, the image of the staff is brought to

    a focus in the plane of the diaphragm using the focusing screw.

    The eyepiece is rotated so that the cross hairs are in focus and

    its focal point is also in the plane of the diaphragm. When

    looking into the telescope an observer will now see a magnified

    image of the levelling staff focused against the cross hairs.

    Figure: Level machine annotations

    Figure: Telescope annotations

    Figure: Object Lens

  • Field Surveying

    4

    The Steps of Leveling:

    The following steps are taken when using a level to measure

    heights:

    1.Set up the tripod

    - Loosen screws of tripod legs, pull out to required length and

    tighten screws.

    - In order to guarantee a firm foothold sufficiently press the

    tripod legs into the ground. When pressing the legs into the

    ground note that the force must be applied along the legs.

    - Check all screws and bolts for correct fit.

    - When setting up the tripod pay attention to a horizontal

    position of the tripod plate. Minor inclinations of the tripod can

    be corrected with the footscrews of the tribrach.

    2.Attach Level on tripod

    - Place level onto tripod head. Tighten central fixing screw of

    tripod.

    - Turn footscrews A and B simultaneously in opposite

    directions until bubble is in the centre (on the imaginary

    "T").

    - Turn the instrument 90 and then turn the foot screw C

    until bubble is centred.

    3.Center instrument over a ground point

    If you want to centre an instrument over a ground point:

    - Attach plumb bob and arrange the tripod in such way that

    the plummet is over the point.

    - For fine adjustment loosen central fixing screw slightly and

    shift instrument parallel on tripod until the plummet is exactly

    over the point.

    - Tighten central fixing screw.

    Figure: Set up the tripod

    Figure: Attach Level on tripod

    Figure: Center instrument over a ground point

  • Field Surveying

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    4. Focusing telescope

    - Aim telescope against a bright background (e.g. white

    paper).

    - Turn eyepiece until reticule is sharp-focused and deep

    black. Now the eyepiece is adapted to your eye.

    - Aim telescope on staff using the coarse aiming device.

    - Turn focusing knob until image of staff is sharply focused.

    5. Levelling staffs (rods) and accessories

    There are many types of staffs, with names that identify the

    form of the graduations and other characteristics. Staffs can be

    one piece, but most of them are sectional and adjust the length

    by telescoping..

    The metric staff has major numbered graduations in meters and

    tenths of meters (there is a tiny decimal point between the

    numbers). Our staves have an ''E'' shape mark (or its mirror

    image) with horizontal spaces between them of 10 mm.

    When viewed through an instrument's telescope, the observer

    can easily visually interpolate a 10 mm mark to a quarter of its

    height, giving a reading accuracy of 2.5 mm. On one side of the

    rod, the colors of the markings alternate between red and black

    with each meter of length.

    The Black arrows indicate where to push to extend the staff to

    its full length.

    6.Staff Reading

    The figure beside shows three different staff readings:

    It is easy to read (b) and (c) because the cross-hair is exactly on a

    mark division. The reading for (a) is between 1.630 and 1.640. To

    assess the mm reading you have to estimate where the position

    of the cross-hair is. For (a) the reading is 1.636. The millimeter

    reading is to be estimated and can very between 1 mm.

    Figure: Focusing Telescope

    Figure: Levelling Staffs

    Figure: Staff Reading

  • Field Surveying

    6

    Points l Fwd distance l Back distance l Mean l Error l Accuracy A l x l y l (x+y)/2 l x-y l ( x-y)/ratio A 1 l x 1 l y 1 l (x+y)/2 l x-y l ( x-y)/ratio A 2 l x2 l y2 l (x+y)/2 l x-y l ( x-y)/ratio

    A 3 l x3 l y3 l (x+y)/2 l x-y l ( x-y)/ratio

    A 4 l x 4 l y4 l (x+y)/2 l x-y l ( x-y)/ratio

    B l x5 l y5 l (x+y)/2 l x-y l ( x-y)/ratio

    Field Results:

    Points l First Trial l Points l Second Trial

    A-A1 l 9m l A-A1 l 7m

    A1-A2 l 9m l A1-A2 l 9m

    A2-A3 l 9m l A2-A3 l 9m

    A3-A4 l 10m l A3-A4 l 7m

    A4-A5 l 12m l A4-A5 l 9m

    A5-B l 13.40m l A5-A6 l 10m

    Total l 62.40m l A6-A7 l 11.40m

    Total l 62.40m

    Field shots:

    Figure: Level Machine

    Figure: Level Machine on Tripod + Levelling Staff

    Figure: Focusing Level Machine + Centering the bubble to maintain horizontality

  • Field Surveying

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    Figure: Measuring Distance by the tape

  • Field Surveying

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