MEASUREMENT OF VERTICAL DISTANCE

Question 1

is the general term applied to any of the various processes by which elevations of points or differences in elevation are determined. It is a vital operation in producing necessary data for mapping, engineering design, and construction.

Answer 1

Leveling

Question 2

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

Answer 2

Vertical Line

Question 3

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

Answer 3

Level Surface

Question 4

A line in a level surface - therefore, a curved line.

Answer 4

Level line

Question 5

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

Answer 5

Horizontal Plane

Question 6

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

Answer 6

Horizontal line

Question 7

Any level surface to which elevations are referred. This is the surface that is arbitrarily assigned an elevation of zero. This level surface is also known as a reference datum

Answer 7

Vertical datum

Question 8

It is the vertical distance of a point above or below an arbitrarily assumed level surface or curved surface.

Answer 8

Elevation

Question 9

It is the vertical distance between the two level surfaces in which the points lie.

Answer 9

Difference in Elevation (DE)

Question 10

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

Answer 10

Bench Marks (BM)

Question 11

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

Answer 11

Turning Point (TP)

Question 12

A rod reading taken on a point of known elevation (BM or TP). It is usually called a plus sight.

Answer 12

Backsight (B.S.)

Question 13

The horizontal distance from level to rod on a B.S.

Answer 13

Backsight Distance (BSD)

Question 14

A rod reading taken on a point of unknown elevation (BM or TP to be established). It is usually called a minus sight.

Answer 14

Foresight (F.S.)

Question 15

The horizontal distance from level to rod on a F.S.

Answer 15

Foresight Distance (FSD)

Question 16

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

Answer 16

Height of Instrument (H.I.)

Question 17

TYPES OF LEVELS

Answer 17

Dumpy Level
Automatic Level
Tilting Level
Laser Level
Digital Level
Hand Level

Question 18

▪ general purpose instrument and commonly referred to as engineer’s level
▪ Provides excellent introduction to levels in general though has been superseded by self leveling instruments

Answer 18

Dumpy Level

Question 19

▪ a.k.a. self-leveling level
▪ like dumpy level it is also regarded as engineer’s level
▪ leveled by the use of a circular spirit or bull’s eye level and the compensator maintains a horizontal line of sight
▪ advantages: light, easy to handle and operation is quick and accurate

Answer 19

Automatic Level

Question 20

▪ can be tilted or rotated about its horizontal axis. ▪ has a level bubble with a sensitivity of 10” per 2 mm division and the images of the bubble ends are viewed through the eyepiece
▪ equipped with coincidence bubbles used for precise leveling

Answer 20

Tilting Level

Question 21

▪ used commonly in construction works to maintain the elevations needed
▪ saves time and effort since it can detect the prism in a whole revolution of 360𝑜
▪ advantage for layout work in construction since it is simple, one button operation and fully automatic general construction

Answer 21

Laser Level

Question 22

Easy
▪ Aims the telescope at the staff, adjust focus and press a single key and it measures height and distance simultaneously
Fast
▪ measurement is completed in < 3 sec.
Accurate
▪ automatic operation eliminates conventional error by the operator.

Answer 22

Digital Level

Question 23

▪ Widely used for rough leveling
▪ Consists of a metal sighting tube about 6 in long on which is mounted a level vial

Answer 23

Hand Level

Question 24

▪ are graduated wooden rods of rectangular section by means of which difference in elevation is measured
▪ some are also in aluminum alloy and fiberglass
▪ lower ground end (usually the point of zero measurement) is shod with metal to protect it from wear

Answer 24

Leveling Rods

Question 25

SOURCES OF ERROR IN LEVELING

Answer 25

Imperfect Adjustment of the Instrument
Parallax
Earth’s Curvature
Atmospheric Refraction
Variations in Temperature
Rod not of Standard Length
Rod not Held Plumb
Faulty Turning Points
Settlement of Tripod or Turning Points
Bubble Not Exactly Centered at Instant of Sighting

Question 26

consists simply of differential leveling with the addition of intermediate minus sights (foresights) taken at required points along the reference line.

Answer 26

Profile Leveling

Question 27

is a curved line which graphically portrays the intersection of a vertical plane with the surface of the earth.

Answer 27

Profile

Question 28

is a numerical designation given in terms of horizontal distance at any point along a profile line away from the starting point.

Answer 28

Stationing

Question 29

These sights, which are also known as ground rod readings, are taken along the centerline of the proposed project to provide an accurate representation of the ground surface.

Answer 29

Intermediate foresights

Question 30

are points which are established along the profile level route at uniformly measured distances. These points are usually made in multiples of 100, 50, 30, 20, or 10 m

Answer 30

Full stations