SUMMARIZD SURVEY NOTES (BASIC)

SUMMARIZED SURVEY NOTES.

Definition of survey:

Survey refers to the science of measuring and recording distances, angles and heights o  the earth’s surface for the purpose of producing maps or plans.

TYPES OF SURVEYING.

1.     Chain survey.

2.    Plane table survey.

3.    Prismatic compass survey.

1.  CHAIN AND TAPE SURVEY.

This is a simple land survey that deals with measuring and recording linear distances on the ground.

            EQUIPMENTS USED IN CHAIN AND TALE SURVEY.

●     The chain:

It’s made up of steel wire with links which are connected by small rings. Normally its length is about 20m or 30m long. It’s used for linear measurements.

●     The tape:

It’s made up of steel, strip or fiberglass. Its length is about 10m to 20m. Also it’s having graduated divisions normally in 10mm. It’s also used to measure linear measurements.

●     A peg:

It’s made up of wood or metal or plastic material. Its about 50cm long. Its having a sharp point for easily derivation into the land. Used to mark permanent position during survey.

·         Ranging rod or pole:

It’s made up of wood or metal or plastic material. It’s about 2m to 3m long. It’s painted alternatively in red and white colors in order to be seen clearly. They are having sharp points for easily derivation into the ground. It’s used to mark temporally points.

·         A surveyor’s band:

It’s made up of steel, strip or fiber glass and rolled into a metal frame with a winding handle. It’s about 30cm long to 100cm.

·         Cross staff:

It’s made up of metal or wood with eye slits and right angles. It’s used to measure the right angles.

·         Arrow:

It’s made up of steel with one circular end. It’s tied with colored cotton material easy to be seen. Used to mark points on the ground.

·         Notebook and pencil:

These are used to record or booking all necessary information during chain survey.

METHODS INVOLVED IN CHAIN SURVEY.

·         The chain is thrown to be extended.

·         A leader takes arrows while followers take rods.

·         Follower erect a rod at the first base point, places a brass handle of a chain against the rod.

·         A leader straightens a chain and inserts an arrow to the end of a brass handle of a chain.

·         A booker books important data.

·         A leader drags a chain so that follower’s end is at the leader’s arrow.

·         The process becomes repeated over and over until the survey reaches I’s climax.

USES OF CHAIN SURVEY.

·         To map a small area this is flat or relative flat.

·         To add details the large scale maps.

·         To find the linear distances on the ground.

·         To find the area of a given land.

·         It is used by land planners.

ADVANTAGES OF CHAIN SURVEY.

·         it is simplest and common method or technique in survey of land.

·         Equipments used can be replaced. Like a tape can replace a chain.

·         It does not involve complicated mathematics.

·         it needs few people to conduct  i. e a leader and a follower.

·         The equipment used in chain survey are simple and they do not involve much knowledge.

DISADVANTAGES OF CHAIN SURVEY.

·         It cannot be conducted in a built area.

·         It is not easy undertaken in density wooded areas.

·         It is inefficient in steep areas.

·         It becomes difficult when it faces obstacles.

·         It consumes time.

PRINCIPLES WHEN CONDUCTING CHAIN SURVEY.

o   Use few chain lines as possible.

o   Avoid steep slope.

o   Keep chain lines short.

o   Select one major line (major line).

o   Maintain all triangles between 30 and 120 degrees.

ERRORS IN CHAIN SURVEY.

Errors in chain survey are mistakes or short coming that happen during the survey process leading to taking wrong measurements.

SOURCES OF ERRORS IN CHAIN SURVEY.

o   Poor reading from the chain.

o   Fault in chain or any chain equipment.

o   Laziness of the surveyor.

o   Sagging of a chain.

o   Incorrect positioning of an arrow along the chain line.

WAYS OF AVOIDING ERRORS.

o   To read carefully from the chain.

o   The surveyor should be serious.

o   To avoid sagging of a chain.

o   To select few chain lines to avoid confusion.

o   To avoid a chain with a fault.

2     PRISMATIC COMPASS SURVEY:

A prismatic compass survey is a survey which employs prismatic compass to measure and record distances and heights as well as bearings of an object.

Prismatic compass is a prism like feature with a hinged lid, sighting slit and a glass prism.

HOW TO USE A PRISMATIC COMPASS.

o   Open the lid and flick up the brass box containing glass prism.

o   Align the object with the prism slit and the hairline on the glass lid.

o   A thin magnetic bar swings toward the magnetic north.

o   Hold the compass properly.

PRECAUTIONS WHEN USING A PRISMATIC COMPASS.

§  Avoid a deposit of magnetic materials.

§  Hold a prismatic compass properly.

§  Avoid wearing a wrist(iron) watch.

§  Avoid a deposit of ferrous materials mainly that of iron.

ADVANTAGES OF A PRISMATIC COMPASS SURVEY.

v  It is quick method in the field.

v  It reduce errors than chain survey

v  A check can be made on both forward and backward bearings.

v  All readings can be made quickly and easily.

v  It can be combined with other methods like chain survey nd plane table survey.

DISAVANTAGES OF PRISMATIC COMPASS SURVEY.

v  It requires areas with no ferrous materials.

v  It requires areas with no magnetic materials.

v  It requires high knowledge.

v  It is difficult to hold a compass properly.

v  It is geological knowledge.

3     PLANE TABLE SURVEY:

This is a survey which deals with measuring ad recording of distances of object using a plane table.

The plane table is simple wooden board about 70cm by 60cm by 1 cm with around brass screw.  The following are its instruments:

v  Tripod stand is three legged frame on which a table is mounted.

v  Alidade is a brass ruler with graduated measurement.

v  Plumbing fork is a bob used to fix a position exactly by pointing down over the ground when it is tied to the clamping screw.

v  Trough compass is a narrow wooden box containing a magnetic needle.

v  Spirit level is an instrument used to insure that  plane table surface is absolutely level.

v  Clamp is an instrument used to board of a table in into a position.

ADVANTAGES OF PLANE TABLE.

a.    It is a quick method.

b.    It is accurate method.

c.    It is used to produce immediate maps.

d.    The map is produced direct and office work is out of the minimum.

e.    It can be carried out in extremely areas.

DISAVANTAGES OF PLANE TABLE.

                      i.        It is not conducted during rainy season.

                    ii.        It needs high knowledge

                   iii.        The scale of drawing is limited by a size of a plane table.

                   iv.        It cannot be conducted in areas with thick forest.

4    LEVELLING SURVEY:

Leveling may be defined as the determination of the relative heights of various points on the earth’s surface.

EQUIPMENTS USED IN LEVELLING SURVEY;

                      i.        LEVELLING STAFF:

This equipment looks like a big ruler about 4 meters long. Used to record differences in heights.

                    ii.        SPIRIT LEVEL:

This is the one of level instruments used for generating horizontal line of sight. It is also used to take readings from the leveling staff. The instrument is put on a tripod stand.

                   iii.        TRIPOD STAND:

This hold a spirit level so that it can a sight  a point horizontally.

           

                   iv.        ABNEY LEVEL:

This is used to measure degrees, percent of grade, topographical elevation and a chainage correction.

            SIGNIFICANCE OF LEVELLING:

a.    To determine the relative heights of various points on the earth’s surface. These heights can be used in the drawing of contour lines.

b.    Production of longitudinal section of roads.

c.    Used to obtain concrete cross sections of man made features at right angles to the longitudinal lines.

DISADVANTAGES OF LEVELLING;

a.    Involves a lot of movements from time to time especially when changing directions and distances.

b.    The datum line accuracy sometimes is made difficult by reference points.

c.    Leveling by using abney level is a very crude and laborious method.

PREPARED BY

Kim saeloum