measurement of horizontal distance midterm

Horizontal Distance

The linear measurement between two points, understood to be the horizontal length, even if the points are at different elevations.

Plane Surveying

The context for the basic operation of linear measurements

Linear Measurements

The fundamental operation involved in determining the distance between two points

Plumb Lines

The distance between points at different elevations is defined as the horizontal length between their plumb lines.

Pacing

A rapid method for checking measurements or determining approximate distances with low precision.

Pace

The length of a single step in walking, measured from heel to heel or toe to toe.

Stride

Equivalent to two paces or a double step

Taping

The common method of measuring horizontal distances by stretching a calibrated tape between two points and reading the indicated distance

Graduated Tape/Calibrated Tape

The instrument used in taping.

Tachymetry (or Tacheometry)

An indirect method of measurement based on the optical geometry of instruments, where distances are computed by trigonometry using subtended intervals and angles.

Transit/Theodolite

Instruments used to measure the subtended intervals and angles in tachymetric measurements.

Graduated Rod/Scale

Used to determine subtended intervals and angles

Stadia Method

A method of finding distance by observing the apparent locations of two stadia hairs on a vertically held rod.

Stadia Hairs

The marks in the telescope through which observations are made on the rod.

Stadia Rod

A rod held vertically at a distant point for observation

Stadia Constant (C)

The distance from the center of the instrument to the principal focus, usually zero for internal focusing telescopes.

Stadia Interval Factor (K)

A factor of the instrument used in the distance formula ($D=Ks+C$)

Stadia Interval (s)

The difference between the upper stadia hair reading and the lower stadia hair reading observed in the field.

Subtense Bar Method

A method where a precisely 2m-long subtense bar is set up at a distant station, and the horizontal angle subtended by the distance between its two targets is measured

Subtense Bar

A precisely 2-meter long instrument with two targets

Subtended Angle ($\alpha$)

The horizontal angle measured by the theodolite that corresponds to the bar's length.

Odometer

A mechanical device (usually a gear train) that counts the number of revolutions of a wheel of a known circumference.

Measuring Wheel

A device with a known circumference attached to an odometer, often used for quickly measuring distances for rough estimation or mapping.