Go Formative Quiz 1 Flashcards
Two types of general lasers
Visible Light Laser and Electronic Level
Three classes of lasers
Fixed, Rotating, Utility
Three types of fixed lasers
pipeline, pocket, carpenter’s laser
Two types of rotating lasers
horizontal plane and vertical plane
Construction Laser Usage
elevations, foundations, structures, decks, finishes, and site work.
Benefits of Laser Usage
productivity, versatility, accuracy, dependability
Laser Field Practices
Use owner’s manual, signal reflection, pipeline deflection, plumb the sensor rod
Differential Leveling
the process of determining the relative elevations of various point; based on the measurement of vertical distances from a level line.
Elevation
vertical distance above a zero datum
Benchmark (BM)
permanent solid point of known elevation
Backsight (BS)
reading on a rod held on a point whose elevation is KNOWN. A first shot that establishes control.
Height of instrument (HI)
the elevation of the level line of sight of the cross hairs in the instrument with respect to the benchmark
Foresight (FS)
A forward shot to determine an elevation of a point: elevation is UNKNOWN.
Turning Point (TP)
point used in the Differential Leveling Process to temporarily transfer the elevation from the HI
Closed Loop
End a level loop at a known benchmark, either the starting BM or another BM
The Theory: BM + BS = HI
Benchmark + backsight = height of instrument
Eliminating Parallax
Look through instrument at a light-colored object; if cross hairs are fuzzy, adjust eyepiece until they are crisp.
HI - FS = TP ELEV
Height of instrument - foresight = turning point elevation
Field book
notebook to record field data
GPS
A Global Navigation Satellite System that allows us to locate things on the surface of the Earth with extraordinary accuracy using a network of 24 satellites that continuously transmit high-frequency radio signals.
Line of sight
At least three satellites must be in view of a receiver to calculate longitude and latitude as a fourth satellite calculates altitude.
DGPS
Differential Global Positioning Service. DGPS offers enhanced locational measurements through the use of radio beacons that provide corrections.
Static Operational Method
A process used to establish reference points such as the CORS location used by NGS.
RTK (Real-Time Kinematic)
A process where corrections are transmitted in real time from a reference receiver at a known location to one or more remote rover receivers.
GPS Orbiting Error
Occasionally a satellite’s reported position doesn’t match its actual trajectory.
GPS’s Poor Geometry
Relative positions of the satellites
Multi-path signals
Signals may be reflected off objects
Clock errors
A receiver’s built in clock is not as accurate as the atomic clock on a navigation satellite.
An atomic clock
This is an extremely accurate timekeeping device powered by a hydrogen atom.
A cesium atom-powered clock
Possesses an error of about one second in 1 million years.
Constellation
The network of orbiting global navigation satellites.
SBAS - Satellite-Based Augmentation System
Employs a network of geostationary satellites and ground stations that enhance a GNSS.
WAAS
North America’s Wide Area Augmentation System
EGNOS
Europe’s European Global Navigation Overlay System
MSAS
Asia’s Multi-transportation Satellite Augmentation System
