Unit 2. Leveling

Question 1

is the process of directly or indirectly measuring vertical distances to determine the elevation of points or their differences in elevations.

Answer 1

Leveling

Question 2

– is a curved surface which is at any point perpendicular to the direction of gravity or the plumb line.

Answer 2

Level Surface

Question 3

– is a curved line in a level surface all points of which are normal to the direction of gravity and equidistant from the center of the earth.

Answer 3

Level Line

Question 4

– is a plane that is tangent to a level surface at a particular point. It is also perpendicular to the plumb line at the same point.

Answer 4

Horizontal Surface

Question 5

– A straight line in a horizontal plane which is tangent to a level line at one point. This line is perpendicular to the direction of gravity at the point of tangency.

Answer 5

Horizontal Line

Question 6

– is a line parallel to the direction of gravity. It is exemplified by the direction taken by a string supporting a suspended plumb bob passing through a point.

Answer 6

Vertical Line

Question 7

– is an imaginary surface of the sea which is midway between high and low tides. It is taken as the reference surface to which most ground elevations are referred.

Answer 7

Mean Sea Level

Question 8

– is any convenient level surface coincident or parallel with mean sea level to which elevations of a particular area are referred. Any surface may be used when relative elevations over a limited area needs to be established.

Answer 8

Datum

Question 9

– for a particular point, its ___ is the vertical distance above or below mean sea level or any other selected datum.

Answer 9

Elevation

Question 10

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

Answer 10

Difference in Elevation

Question 11

is the process of determining the difference in elevation between two or more points some distance apart.

Answer 11

Differential Leveling

Question 12

– a fixed point of reference whose elevation is either known or assumed. They may be permanent or temporary.

Answer 12

Benchmark (BM)

Question 13

– reading taken on a rod held on a point of known or assumed elevation. First rod reading taken after the instrument has been set up and leveled.

Answer 13

Backsight (BS)

Question 14

– reading taken on a rod held on a point whose elevation is to be determined. Usually taken in the direction in which the leveling work proceeds.

Answer 14

Foresight (FS)

Question 15

– distance from the center of the instrument to the rod on which a backsight/foresight is taken.

Answer 15

Backsight Distance (BSD) / Foresight Distance (FSD)

Question 16

– an intervening point between two benchmarks upon which a point between two benchmarks upon which point foresight and backsight rod readings are taken to enable a leveling operation to continue from a new instrument position.

Answer 16

Turning Point (TP)

Question 17

–elevation of the line of sight of an instrument above or below a selected reference datum.

Answer 17

Height of Instrument (HI)

Question 18

is the process of determining difference in elevation along a fixed line at designated short measured intervals.

Answer 18

Profile Leveling

Question 19

It is executed to provide data from which a vertical section
of the ground surface can be plotted.

Answer 19

Profile Leveling

Question 20

– a curved line which graphically portrays the intersection of a vertical plane with the surface of the earth and the horizontal distances between the points along a surveyed line.

Answer 20

Profile

Question 21

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

Answer 21

Stationing

Question 22

– taken along the centerline of the proposed project to provide accurate representation of the ground surface.

Answer 22

Intermediate Foresights

Question 23

– points established along the profile level route at uniformly measured distances.

Answer 23

Full Stations

Question 24

any intermediate point established along a
profile level. Mostly for location of critical points.

Answer 24

Plus Stations

Question 25

– drawing the vertical scale for a profile much larger than the horizontal scale to accentuate differences in elevation.

Answer 25

Vertical Exaggeration

Question 26

is employed to determine the difference in elevation between two points when it is difficult or impossible to keep backsights and foresights short and equal.

Answer 26

Reciprocal Leveling

Question 27

In the method of levelling, two sets of rod readings are observed.

Answer 27

Reciprocal Leveling

Question 28

is a method of determining differences in elevation between points by employing two level routes simultaneously.

Answer 28

Double-Rodded Leveling

Question 29

It is a method of determining differences in elevation wherein three
horizontal hairs (or threads) are read and recorded rather than a single
horizontal hair. The average of the three readings is taken as the correct
value.

Answer 29

Three-Wire Leveling

Question 30

-The effects of ___ are taken into account in leveling work since the measurements are made in vertical planes and these effects all occur in the same plan.

Answer 30

Curvature and Refraction

Question 31

The ___ of the earth is to increase the rod reading. It, however, occurs in extra long sights and when back sight and foresight distances are not made equal.

Answer 31

effect of curvature

Question 32

Due to the earth’s curvature, a horizontal line departs from a level line by ___, varying as the square of the length of the line. This is based on the mean radius of the earth which is 6371 km.

Answer 32

0.0785 m (7.85cm) in one kilometer

Question 33

When a ray of light passes through air strata of different densities, it is refracted or bent towards the denser medium. This bending is referred to as ___.

Answer 33

refraction

Question 34

The combination of the earth’s curvature and atmospheric refraction causes the telescope’s line of sight to vary from a level line ___.

Answer 34

by approximately 0.0785 minus 0.0110 or 0.0675 m in one kilometer

Question 35

Used in areas of very steep or rugged terrain or when you have inaccessible points.

Answer 35

Trigonometric leveling

Question 36

The ___ provides a faster method of leveling in rough and hilly terrain
where a high degree of precision is not required.

Answer 36

STADIA LEVELING

Question 37

Common Errors and Mistakes in Leveling (5)

Answer 37

Misreading The Rod- the instrument-man reads the rod incorrectly. This mistake most frequently occurs when the line of sight to the rod is partially obstructed by vegetation or other objects in the field.

Incorrect Recording- the recorder should always call out the readings as he records them in order to prevent the recording of incorrect values. It is important that the recorder understands the leveling process. He should be able to visualize the operation for which he makes his recordings.

Erroneous Computations- although level notes only require simple additions and subtractions, mistakes in these computations are still committed. For this reason, mathematical checks should always be performed to ensure that only correct values are determined.

Rod Not Fully Extended- it is important that it is fully extended when reading the high (or long) rod. The two sliding sections should lock properly into position. The clamp should also be tightened firmly to avoid the upper portion of the rod from sliding downward.

Moving Turning Points- A turning point carelessly or accidentally moved out of its position by a rodman will cause a serious mistake in leveling work. This mistake could be prevented by using only stable and clearly defined turning points or by marking the position of the rod with paint, lumber crayon, or chalk.

Question 38

Used in areas of very steep or rugged terrain or when you have inaccessible points.

Answer 38

Trigonometric leveling

Question 39

provides a faster method of leveling in rough and hilly terrain where a high degree of precision is not required.

Answer 39

STADIA LEVELING

Question 40

The process involved is very identical to that in differential leveling. The main difference is that the line of sight does not have to be brought to a horizontal position as in differential leveling.

Answer 40

STADIA LEVELING

Question 41

are taken into account in leveling work since the measurements are made in vertical planes and these effects all occur in the same plan.

Answer 41

Curvature and Refraction

Question 42

The ___ of the earth is to increase the rod reading. It, however, occurs in extra long sights and when back sight and foresight distances are not made equal.

Answer 42

effect of curvature

Question 43

Due to the earth’s curvature, a horizontal line departs from a level line by ___ in one kilometer, varying as the square of the length of the line. This is based on the mean radius of the earth which is ___.

Answer 43

0.0785 m; 6371 km

Question 44

When a ray of light passes through air strata of different densities, it is refracted or bent towards the denser medium. This bending is referred to as ___.

Answer 44

refraction

Question 45

The combination of the earth’s curvature and atmospheric refraction causes the telescope’s line of sight to vary from a level line by ___ in one kilometer.

Answer 45

approximately 0.0785 minus 0.0110 or 0.0675 m