Lecture 8 Chain Surveying

To accurately measure an area using only linear measurements.

Drones are not used in chain surveying; this method relies on physical chains and tapes.

Engineer's chain and surveyor's chain (also known as Gunter's chain) are the main chains used for measurements.

Tally markers indicate specific measurement points along the chain, often at whole meter intervals.

Engineer's chain that is designed for durability and suitable for small surveys.

A Steel Band generally has a width of $13 mm$.

A tape is for accurately measuring distances between points in surveying.

Linen tapes should not be used where great accuracy is required because they can stretch or shrink.

Arrows mark temporary survey stations or points on the ground for measurement.

Pegs mark permanent survey points, such as intersections of survey lines.

Ranging rods mark points and enhance visibility, aiding in establishing straight lines.

Optical squares are used for accurately setting out lines, especially perpendicular ones.

A clinometer measures angles of ground slopes or vertical angles.

It measures slopes more precisely than a clinometer.

Primary triangulation networks are established to measure angles with high accuracy (±3).

The primary trig points were fixed at the corners of triangles.

Points are established at closer intervals and connected into primary triangles.

Using Electronic Distance Measurement (EDM) equipment.

To minimize errors when computing check base lines.

Triangulation is best suited in open, hilly country.

Steel bands/tapes should be reeled up when not in use to protect them from damage.

Station marking facilitates easy relocation of survey stations if they are moved or obscured.

Witnessing facilitates easy re-location of a station at a later date by recording its surroundings.

Offsets are taken perpendicular to chain lines to accurately map features that are not directly on the line.

Helps form a strong base on which to build triangles thus reducing error propagation.

To help ensure the accuracy of the survey, angles should be well-conditioned.

Check lines help save time and avoid unnecessary duplication of lines.

Ranging creates a straight line between two points for accurate measurement.

Gross errors are significant mistakes due to carelessness or incompetence.

Because even with the best equipment and methods, small variations and imperfections exist.

Calibrating the observing equipment helps to identify and correct systematic errors.

Random errors, due to their unpredictable nature, cannot be entirely removed.

Systematic errors are mainly caused by badly adjusted instruments.

Tension correction accounts for the effects of tension on the length of the chain or tape.

Adopting statistical principles helps understand the magnitude and distribution.

Systematic errors have a cumulative effect in a series of repeated measurements under the same conditions.