Geodesy and Coordinate Systems
This domain tests datum literacy: NAD83(2011) versus the retiring NSRS, NAVD88 heights and the geoid, Missouri's three State Plane zones, and the grid-versus-ground conversion you must get right on any project deliverable.
Core concepts
NAD83(2011) at epoch 2010.0 is a GRS80-based horizontal realization; NGS is replacing it with NATRF2022, and NAVD88 with NAPGD2022. Ellipsoid height minus geoid undulation gives orthometric height; in Missouri the geoid undulation is roughly −30 m, so a GNSS ellipsoid height must be corrected with GEOID18 before it means anything in NAVD88. Missouri State Plane uses Lambert Conformal Conic in three zones (East, Central, West). Grid distances are not ground distances.
Worked example
A 1,000.000 ft ground distance at elevation 600 ft, with a point scale factor of 0.99992000. Elevation factor = R/(R+h) = 20,906,000/(20,906,600) = 0.9999713. Combined factor = 0.9999713 × 0.9999200 = 0.9998913. Grid distance = 1,000.000 × 0.9998913 = 999.891 ft - a 0.109 ft difference. When you publish State Plane coordinates, publish grid; when you stake on the ground, use ground distances and say which is which in your report.
Traps
Mixing NAD27 and NAD83 coordinate values; reporting SPCS coordinates without stating the epoch and realization; applying only the scale factor and forgetting elevation; and using RTK-derived heights as NAVD88 without a geoid model check. Also watch the arc-to-chord correction on long sight lines and the difference between a localization and a true datum transformation.