Spectra Precision Survey Pro v4.6 Recon and Nomad User Manual User Manual

Page 244

User’s Manual – GPS Mode

234

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apply. When a vertical coordinate is required, most survey projects

require orthometric elevations.

• Lat, Lng, Ht

Geodetic horizontal coordinates are usually

expressed as two angles called latitude and
longitude (φ, λ). Geodetic vertical coordinates

are usually expressed as the distance above the

ellipsoid called height. The angles describe a
point’s position on the surface of the reference

ellipsoid. The height describes the altitude

normal to the surface of the reference ellipsoid.

• ECEF XYZ

Geodetic coordinates are sometimes given in
the Earth Centered Earth Fixed (ECEF)

Cartesian coordinate system. This coordinate
system has its origin at the Earth’s center of

mass, the primary (Z) axis is the earth’s spin

axis; the secondary (X) axis is the intersection
of the equatorial plane and the mean meridian

of Greenwich; the tertiary (Y) axis is
orthogonal in a right handed system. An ECEF

XYZ coordinate can be converted into the

corresponding lat, lng, ht using standard
formulas.
For many surveying applications, the

horizontal and vertical coordinate systems are
separate. Below are descriptions of common horizontal and vertical

coordinate systems used in surveying and mapping.

Fig. 2: Earth Centered Earth

Fixed Geodetic Coordinates

Fig. 1: Ellipsoidal Geodetic

Coordinates

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