FoS

PACING

one of the simplest methods of measuring distances.

PACING

used in instances where approximate results can be enough for the data needed, such as getting the rodman in position during a cross-section survey, or simply measuring a relatively short distance where accuracy is not that of an issue

PACE

Length of a step

STRIDE

A double step

PACE FACTOR

The distance covered by one pace

FACTORS AFFECTING LENGTH OF PACE

Speed of pacing

Roughness of the ground

Weight of clothing and shoes used Fatigue on part of the pacer

Slope of the terrain

Age and sex of the individual

TACHYMETRY

surveying method used to quickly determine the horizontal distance to, and elevation of, a point

STADIA METHOD

introduced by James Watt

RELATIVE PRECISION

1/300 to 1/1000

FACTORS AFFECTING PRECISION

• Refinement with which the instrument was manufacture •Roughness of the ground

• Skill of the observer

• Fatigue on part of the pacer

• Length of measurement effects of refraction and parallax

• Age and sex of the individua

TAPING

the use of a graduated tape is the most common method of measuring • horizontal distances

CHAINING

measurement of distances using chains

CHAINMEN

persons undertaking measurement using chains

6 STEPS IN TAPING ON LEVEL GROUND USING TAPE

• Lining in

• Applying Tension

• Plumbing

• Making Tape Length

• Recording Tape

• Recording Distance

LEVELING

general term applied to any of the various processes by which elevations of points or differences in elevation are determined.

LEVELING RESULTS ARE USED TO:

1\.Design highways, railroads, canals, sewers, water supply systems, and \[other facilities having grade lines that best conform to existing topography 2.. Lay out construction projects according to planned elevations. 3.Calculate volumes of earthwork and other materials.

4.. Investigate drainage characteristics of an area.

5\. Develop maps showing general ground configurations.

6\. Studv earth subsidence and crustal motion.

VERTICAL LINE

A line that follows the local direction of gravity as indicated by a plumb line.

LEVEL SURFACE

A curved surface that at every point is perpendicular to the local plumb line (the direction in which gravity acts).

LEVEL LINE

Line in a level surfacetherefore, a curved line

HORIZONTAL PLANE

A plane perpendicular to the local direction of gravity. In plane surveying, it is a plane perpendicular to the local vertical line.

HORIZNTAL LINE

A line in a horizontal plane. In plane surveying, it is a line perpendicular to the local vertical

VERTICAL DATUM

Any level surface to which elevations are referenced. This is the surface that is arbitrarily assigned an elevation of zero. This level surface is also known as a reference datum since points using this datum have heights relative to this surface.

ELEVATION

The distance measured along a vertical line from a vertical datum to a point or obiect. If the elevation of point A is 802.46 ft. A is 802.46 ft above the

GEOID

\- A particular level surface that serves as a datum for all elevations and astronomical observations

MEAN SEA LEVEL

The average height for the surface of the seas for all stages of fide over a 19-year period as defined by fhe National Geodetic Vertical Datum of 1929, usually taken at hourly intervals, at 26 gaging stations along the Atlantic and Pacific oceans and the Gulf of Mexico. The elevation of the sea differs from station to station depending on local influences of the tide.

TIDAL DATUM

The vertical datum used in coastal areas for establishing property boundaries of lands bordering waters subject to tides. A tidal datum also provides the basis for locating fishing and oil drilling rights in tidal waters, and the limits of swamp rocks

BENCHMARK

\- A relatively permanent object, natural or artificial, having a marked point whose elevation above ot below a reference datum is known or assumed. Common example are metal disks set in concrete, reference marks chiseled on large rocks, non movable parts of hydrants, curbs, etc

LEVELING

The process of finding elevations of points or their differences in elevation.

VERTICAL CONTROL

\- A series of benchmarks or other points of known elevation established throughout an area, also termed basic control or level control.

DIRECT OR SPIRIT LEVELING

By measuring vertical distances directly. Direct leveling is the most precise method of determining elevations and is the one commonly used

INDIRECT OR TRIGONOMETRIC LEVELING

By measuring vertical angles and horizontal or slope distances.

RECIPROCAL LEVELING

Is the process of accurately determining the difference in elevation between two intervisible points located at a considerable distance apart and between which points leveling could not be performed in the usual h manner.

PROFILE LEVELING

To determine differences in elevation between points at designated short measured intervals along an established line to provide data from which a vertical section of the ground surface can be plotted.

STADIA LEVELING

Combines features of direct leveling with those of trigonometric leveling.

BAROMETRIC LEVELING

Involves the determination of differences in elevation between points by measuring the variation in atmospheric pressure at each point by means of a barometer.

CROSS-SECTION LEVELING

In highway construction It is often necessary to obtain a representation of the ground surface on either side of the centerline

BORROW PIT LEVELING

Is a method of determining the relative elevations of points in borrow pit excavations for the purpose of calculating volumes of earthwork.

AUTOMATIC LEVEL

Is an optical instrument used to establish or verify points in the same horizontal plane. It is used in surveying and building with a vertical staff to measure height differences and to transfer, measure and set heights.

LEVELING ROD

Is a graduated rod which is used for measuring the vertical distance between the line of sight through a leveling instrument and the point whose elevation is either required or known

TRIPOD

Serve as a base to prevent movement of the instrument after it is set-up. The leg are spread wide enough to provide a stable platform for the instrument

INSTRUMENTAL ERROR

o Line of Sight

o Cross hair exactly horizontal o not exactly horizontal

o Rod length not correct

o Tripod legs loose

PERSONAL ERROR

o Bubble not centered

o Parallax o Faulty rod reading

o Rod handling

o Target setting

NATURAL ERROR

o Curvature of the Earth o Refraction o Temperature Variation o Wind o Settlement of the Instrument o Settlement of a turning point

COMMON MISTAKES IN LEVELING

• Misreading the rod

• Incorrect recording

• Erroneous computations

• Rod not fully extended

• Moving turning points

Curvature error

divergence between a level line and a horizontal line over a specified distance.

DIFFERENTIAL LEVELLING

is the operation of determining the elevations of points some distance apart. Usually, this is accomplished by direct leveling (Davis, et al., 1981)

DIFFERENTIAL LEVELING

requires a series of setup of the instrument along the general route and for each setup, a rod reading back to a point of known elevation and forward to a point of unknown elevation.

BENCH MARK (BM)

definite point on an object, the elevation and location of which are known

TURNING POINT (TP)

\- intervening point between two bench marks upon which point foresight and backsight rod readings are taken

BACKSIGHT (BS)

rod reading taken on a point of known elevation; sometimes called a plus sigh

FORESIGHT (FS)

rod reading taken on a point the elevation of which to be determined; sometimes called a minus sight

(HI)HEIGHT OF INSTRUMENT

elevation of the line of sight of the of the telescope above the datum when the instrument is leveled.

THREE-WIRE LEVELING

Consists in making rod readings on the upper, middle, and lower crosshairs

ADVANTAGES OF THREE WIRE LEVELING

(1) providing checks against rod reading blunders, (2) producing greater accuracy because averages of three (readings are available, and (3) furnishing stadia measurements of sight lengths to assist in balancing backsight and foresight distances

a

upper stadia hair reading

b

lower stadia hair reading

c

horizontal cross –hair reading or rod reading on P

s

stadia intercept or the difference between the upper stadia hair reading and the lower stadia hair reading

m

mean of three hair readings

HD

horizontal distance from the level to the rod held at P

K

stadia interval factor

C

instrument constant

HI

height of the line sight of above the datum or sea level

ELEV OF P

unknown elevation of station P

ERROR OF CLOSURE

When a line of level makes a complete circuit, almost invariably the initial level of the BM is not equal to the final level

ERROR OF CLOSURE

This difference is the error of running the circuit

4 TYPES OF MERIDIAN

1. True Meridian
2. Magnetic Meridian
3. Grid Meridian
4. Assumed Meridian

EXPEDIENT METHODS OF ESTABLISHING MERIDIANS

1. Establishing Magnetic Meridian by Compass
2. Determining True North by Aid of Sun and a Plumb Line
3. Determining True North by the Rising and Setting of the Sun
4. Determining True North by Polaris
5. Determining True South by the Southern Cross
6. Determining Direction of True North or South by a Wrist Watch

360°.

1 𝑅𝑒v (degree)

360°.

400g (grad)

into 6400 parts called mils

Mil - the circumference is divided

360°.

6400 mils (mil)

360

2𝜋 𝑟𝑎d (radian)

INTERIOR ANGLES

The angles between adjacent lines in a closed polygon are called interior angles.

(n-2) (180)

the sum of interior angle is equal to

EXTERIOR ANGLES

An explement is the difference between 360 degrees and any one angle

DEFLECTION ANGLES

The angle between a line and the prolongation of the preceding line

BEARINGS

The direction of a line may be described by gibing its bearing. The bearing of a line is the acute horizontal angle between the reference meridian and the line

FORWARD BEARINGS

When the bearing of a line is observed in the direction in which the survey progresses,

BACK BEARINGS

if the bearing of the same line is observed in an opposite direction

AZIMUTHS

s its direction as given by the angle between the meridian and the line measured in a clockwise direction from either the north or south branch of the meridian.

AZIMUTHS

usually preferred over bearings by most surveyors because they are more convenient to work with such as in computing traverse data by electronic digital computers. 'lite azimuth of a line may range from 0 to 360 degrees

RULE 1 (FORWARD AND BACK AZIMUTHS)

If the forward azimuth of the line is greater than 180 degrees, subtract 180 degrees to obtain the back azimuth

RULE 2 (FORWARD AND BACK AZIMUTHS)

When the forward azimuth of the line is less than 180 degrees, add 180 degrees to determine the back azimuth