Life Cycle of Control Point Positions: A Case Study Using a Multi-State Control Point Database (MCPD)

Abstract

The life-cycle (usability) of a control point's position is tied closely to the control point's stability, its datum, and velocity changes across a region due to crustal movement. Analyses of the coordinates of numerous control points stored in the Idaho and Montana Multi-State Control Point Database (<small>MCPD</small>) showed no statistical differences due to a point's stability and its physical setting. However, analyses comparing various realizations of horizontal datum revealed some significant differences. Specifically, there is >1 m difference observed between coordinates using <small>NAD</small> 83(1986) relative to <small>NAD</small>83(2011) and approximately 2 cm difference between <small>NAD</small> 83(CORS96) and <small>NAD</small> 83(2011) coordinates. A comparison of vertical coordinates derived from geoid models revealed a 30 cm mean difference between <small>GEOID</small>03 and <small>GEOID</small>12A, and >60 cm difference between <small>GEOID</small>99 and <small>GEOID</small>12A. The impact of velocity on these coordinates was apparent and varies strongly with local tectonics across the eastern Idaho study area. This study supports the <small>NGS</small> recommendation to use the most current realization of horizontal and vertical datum available.