Surveying Instruments

What is a total station?

Electronic surveying instrument combining electronic theodolite with EDM, measuring angles and distances simultaneously.

What is a robotic total station?

Motorized total station that automatically tracks a prism, allowing single-person operation.

What is an automatic level?

Level with internal compensator that automatically maintains horizontal line of sight when approximately level.

What is a digital level?

Level that automatically reads bar-coded rod and records elevations electronically.

What is a compensator?

Optical-mechanical device in automatic levels maintaining horizontal line of sight when instrument is approximately level.

What is an electronic theodolite?

Theodolite with electronic angle encoders and digital displays, typically reading to 1 arc-second.

What is an angle encoder?

Electronic device converting angular rotation to digital values, replacing graduated circles in modern instruments.

What is an EDM?

Electronic Distance Meter - determines distance by measuring travel time of electromagnetic waves.

What is reflectorless EDM?

EDM measuring to surfaces without prism using time-of-flight laser pulses. Reduced range compared to prism measurements.

What is a prism constant?

Offset between physical center of reflector prism and effective reflection point. Must be entered in EDM for accurate distances.

What is a tribrach?

Detachable base of surveying instrument containing leveling screws and connection to tripod.

What is an optical plummet?

Device in theodolite or tribrach allowing precise centering over a point by viewing downward through the instrument.

What is a Philadelphia rod?

Commonly used leveling rod with graduations in feet, tenths, and hundredths, extending to 7 or 12+ feet.

What is an invar rod?

Precision leveling rod made of low thermal expansion invar alloy for first and second-order leveling.

What is zenith angle?

Vertical angle measured downward from vertical (zenith = 0°). Related to vertical angle: VA = 90° - ZA.

What is collimation in instruments?

Process of aligning optical axis. Also refers to the line of sight through the telescope.

What is parallax?

Apparent movement of target image relative to crosshairs due to improper focus. Must be eliminated for accurate readings.

What is a peg test?

Field procedure to determine and adjust collimation error in a level by comparing readings from equidistant and unequal setups.

What is a two-peg test?

Field procedure to check and adjust collimation of a total station using two stable points.

What is face left/face right?

Observations made with telescope in normal and reversed positions to eliminate systematic instrumental errors.

What is plunge?

Rotating telescope about horizontal axis to view in opposite direction. Used for face left/face right observations.

What is a laser plane?

Rotating laser beam establishing horizontal or sloped reference plane for grade control over large areas.

What is machine control?

GPS/GNSS or robotic total station systems that automatically guide construction equipment to design grades.

What is 3D laser scanning?

Technology using laser pulses to capture millions of surface points for creating 3D models.

What is UAV surveying?

Using Unmanned Aerial Vehicles (drones) with cameras or LiDAR for aerial mapping and surveying.

What atmospheric corrections affect EDM?

Temperature and pressure deviations from standard conditions (typically 15°C and 1013.25 hPa) require corrections.

What is the standard temperature for EDM?

Most EDM instruments are calibrated for 15°C (59°F) and require temperature correction for other conditions.

How does EDM work?

Measures phase shift or time-of-flight of modulated light or microwave signal reflected from prism or surface.

What is index error in a theodolite?

Systematic error in vertical circle reading caused by misalignment of zero mark.

What limits reflectorless EDM range?

Surface reflectivity, angle of incidence, and ambient light conditions. Typically 100-1000m vs 3000m+ with prism.