Theme: Geodesy

Temporal change

See also: Geoid § Temporal change

In geodesy, temporal change can be studied by a variety of techniques. Points on Earth's surface change their location due to a variety of mechanisms:

• 
  Continental plate motion, plate tectonics^[5]
  
• 
  Episodic motion of tectonic origin, especially close to fault lines
  
• 
  Periodic effects due to tides and tidal loading^[6]
  
• 
  Postglacial land uplift due to isostatic adjustment
  
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  Mass variations due to hydrological changes, including the atmosphere, cryosphere, land hydrology and oceans
  
• 
  Sub-daily polar motion^[7]
  
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  Length-of-day variability^[8]
  
• 
  Earth's center-of-mass (geocenter) variations^[9]
  
• 
  Anthropogenic movements such as reservoir construction or petroleum or water extraction
  

The science of studying deformations and motions of Earth's crust and its solidity as a whole is called geodynamics. Often, study of Earth's irregular rotation is also included in its definition. The geodynamics studies require terrestrial reference frames^[10] that are realized by the stations belonging to the Global Geodedetic Observing System (GGOS^[11]).

Techniques for studying geodynamic phenomena on the global scale include:

• 
  Satellite positioning by GPS, GLONASS, Galileo, and BeiDou
  
• 
  Very-long-baseline interferometry (VLBI)
  
• 
  Satellite laser ranging (SLR)^[12] and lunar laser ranging (LLR)
  
• 
  DORIS
  
• 
  Regionally and locally precise levelling
  
• 
  Precise tacheometers
  
• 
  Monitoring of gravity change using land, airborne, shipborne, and spaceborne gravimetry
  
• 
  Satellite altimetry based on microwave and laser observations for studying the ocean surface, sea level rise, and ice cover monitoring
  
• 
  Interferometric synthetic aperture radar (InSAR) using satellite images
  

Reference:

1. 
    "geodesy | Definition of geodesy in English by Lexico Dictionaries". Lexico Dictionaries | English. Retrieved 2019-08-15.
   
2. 
   ^ "What Is Geodesy". National Ocean Service. Retrieved 8 February 2018.
   
3. 
   ^ Foroughi, Ismael; Tenzer, Robert (2017). "Comparison of different methods for