Chapter 4 Notes on Horizontal Distance Measuring

Vocabulary flashcards covering key concepts and terms from Chapter 4 on Horizontal Distance Measuring in surveying.

Direct Measurement

Measuring a value directly with a device such as a measuring wheel, tape, or total station.

Indirect Measurement

Measuring a value that is found through its relationship to another measured quantity.

Pacing

A rough measuring method involving counting steps to estimate distance, with an accuracy ratio of 1/50 to 1/100.

Measuring Wheel

A measuring device with dials to read distances, typically used for rough or preliminary measurements (also known as an odometer wheel).

Invar Tapes

Measuring tapes made of an invar alloy (nickel-steel) known for its very low coefficient of thermal expansion, used for high-precision measurements.

Steel Tapes

Common measuring tapes made of steel, prone to expansion and contraction with temperature changes, requiring corrections for accuracy.

Breaking Tape

A technique used for measuring distances on steep slopes by chaining in short increments, holding the tape horizontal for each increment.

Corrections in Taping

Adjustments needed to account for factors like temperature, tape length discrepancies, sag, and alignment when using measuring tapes.

Stationing

A method of designating locations along a survey line or baseline, typically in even increments (full stations) and partial increments (plus stations).

Full Stations

Points along a survey line located at even increments (e.g., every 100 feet or meters), denoted by whole numbers (e.g., 1+00).

Plus Stations

Intermediate points located between full stations, denoted by a full station number plus an additional distance (e.g., 1+25 for 25 feet beyond station 1+00).

Grade

The slope of a terrain or a constructed surface, expressed as a ratio (e.g., 1:50) or a percentage (e.g., 2\%).

Rate of Grade

The change in elevation per unit of horizontal distance, often expressed as a percentage or ratio of vertical change (V) to horizontal distance (H), i.e., (V/H) \times 100\% or V:H.

Slope Distance

The distance measurement along a sloping surface, measured along the hypotenuse of a right-angled triangle formed by the horizontal distance and vertical elevation difference.

Horizontal Distances

The projection of distances onto a horizontal plane, which is the standard for most surveying measurements.

Stadia Method

An indirect measuring technique using a transit (or theodolite) and a level rod to measure distance, direction, and elevation through observing rod intercepts.

Stadia Interval

The difference in rod readings between the upper and lower stadia hairs (also known as stadia intercept), used to derive horizontal distance in the stadia method.

Stadia Ratio / Constant

The constant factor (typically 100 for external focusing telescopes) by which the stadia interval on the rod is multiplied to obtain the horizontal distance, often expressed as K=100 (e.g., an interval of 1 foot on the rod corresponds to 100 feet of horizontal distance with this ratio).

Deflection Angles

Angles measured from the prolongation of the preceding line to the succeeding line, used to define the direction of survey lines in traversing.