Geodetic Datums & Coordinate Systems Flashcards

What is the combined scale factor (CSF) used for in State Plane coordinate computations?

Answer: Converting ground distances directly to grid distances

The combined scale factor (elevation factor × grid scale factor) converts ground distances directly to grid distances in SPCS.

In the context of geodetic datums, what does 'realization' refer to?

Answer: The set of coordinates and velocities assigned to physical monuments that define the datum in practice

A datum realization is the practical embodiment of a reference system through coordinates assigned to physical control stations.

Which angular measurement defines a point's position in the direction perpendicular to the equatorial plane on a geodetic ellipsoid?

Answer: Geodetic latitude

Geodetic (ellipsoidal) latitude is the angle between the ellipsoidal normal at a point and the equatorial plane.

What is the approximate semi-major axis (a) of the GRS80/WGS84 ellipsoid?

Answer: 6,378,137 m

The semi-major axis of both GRS80 and WGS84 is defined as exactly 6,378,137.0 meters.

The convergence angle (γ) in a State Plane coordinate system is the angular difference between:

Answer: Grid north and true (geodetic) north

Convergence is the angle from grid north to true geodetic north at a given point, required to convert between grid and geodetic azimuths.

Which NAVD 88 vertical datum constraint was used when the 1991 least-squares adjustment was performed?

Answer: A single tidal gauge at Father Point/Rimouski, Quebec held fixed

NAVD 88 was constrained by holding only the Father Point/Rimouski, Quebec tidal gauge fixed as a minimum constraint.

When converting ECEF (Earth-Centered Earth-Fixed) Cartesian coordinates (X, Y, Z) to geodetic coordinates (φ, λ, h), which coordinate directly gives geodetic longitude?

Answer: arctan(Y/X)

Geodetic longitude λ = arctan(Y/X), measured in the equatorial plane from the Greenwich meridian.