Land Subsidence in Miami Beach Based on Precise Leveling Measurements
Method
Land subsidence has been monitored using different geodetic measurements, which are fundamental to the understanding and controlling of this hazard. The oldest method used to measure subsidence is spirit leveling, which is a precise way to determine the elevation of small areas (Sneed, 2018). Another traditional geodetic measurement is geodetic leveling, which requires metric rods and levels to produce accurate elevations, even over large areas. More advanced space geodetic techniques include Global Positioning Systems (GPS) (Sneed et al., 2001) and Interferometric Synthetic Aperture Radar (InSAR) (Wang et al., 2015).
The current study relies on precise geodetic leveling, which is an accurate method of differential leveling using highly accurate and calibrated levels. It is used to determine elevations with respect to a reference level, as mean sea-level, and creates a web of vertical control points. It calculates the difference in elevation between two or more points on the ground surface. Precise leveling has been used in the United States since approximately 1856 - 1857 (Berry, 1976). This method attempts to reduce the magnitude of the observational errors by frequent and careful adjustment and calibration of the instrument system, which minimizes or completely eliminates the calculation of systematic corrections (Berry, 1976).
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