Spectra Precision Survey Pro CE v3.60 GPS User Manual - Manual (Page 12)

GPS User’s Manual
8
G
re
en
w
ic
h
M
er
id
ia
n
Equator
φ
λ
X
Z
Y
h
Coordinate Systems
A coordinate system is a way to describe positions in a datum.
Coordinate systems range from simple Cartesian (y,x) or (N,E)
positions on a flat plane to complex geodetic latitudes and longitudes
on a reference ellipsoid.
Below is a description of some coordinate systems common in
surveying:
• Northing, Easting, Elevation
Survey projects usually use simple plane coordinates. We assume our
local datum models a flat earth, and we calculate coordinates in a
Cartesian system where the simple laws of plane trigonometry 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.
Fig. 1: Ellipsoidal Geodetic
Coordinates