Datums, coordinate systems and satellite positioning: the ellipsoid and the geoid, NAD 83 and NAVD 88 and their modernized successors, State Plane, and how GNSS observations are made and processed.
What this subject area expects
Distinguish ellipsoid height, orthometric height and geoid height, and relate them
Explain the difference between a horizontal datum, a vertical datum and a projection
Apply grid, elevation and combined factors between ground and grid distances
Describe static, RTK and network-RTK observation methods and their error sources
Topics covered here
Ellipsoid, geoid and terrain · Ellipsoid, orthometric and geoid heights · Horizontal and vertical datums · NSRS modernization · State Plane Coordinate System · Grid, elevation and combined factors · Ground and grid distances · Convergence and grid azimuth · UTM and low-distortion projections · US survey foot and international foot · GNSS signals and observables · GNSS field methods and processing · GNSS error sources and quality
Question 1 of 5Geodesy & GNSS · Analyze
A GNSS observation on a proposed pond outlet gives an ellipsoid height h = 1,254.37 m. The geoid model interpolates N = −26.55 m there.
The design elevation for the outlet is stated as an orthometric height. What orthometric height does this observation represent?