Genesys ADMA-G - Relative, Metric Coordinate System

ADMA 3.0
USER MANUAL
Document Revision 2.01 | 2021 Page 85/137
10.6 Relative, metric coordinate system
For some applications, it is not useful to specify positions in terms of decimal degrees of longitude
and latitude. In this case it would be more helpful to specify positions in meters, for example, to
indicate braking distances, radii of steady state circular tests and track deviations.
If the radius of action on the earth's surface is limited (10-50 km, depending on the required accuracy),
the earth's curvature and its effects can be neglected within this range, permitting the establishment
of a planar, metric coordinate system relative to a reference point. This reference point (specified in
decimal degrees) constitutes the zero-point of the metric coordinate system used as a basis by
conversion formulae (decimal degrees to meters).
In this case:
N
SF
= North-scale factor for conversion (m/decimal degrees) at the reference point
E
SF
= East-scale factor for conversion (m/decimal degrees) at the reference point
L = Degree of latitude
L0 = Reference degree of latitude
 = Longitude
0 = Reference degree of longitude
N
R
= North curvature radius (WGS84) at the reference point
E
R
= East curvature radius (WGS84) at the reference point
PosX = Relative position in meters northward
PosY = Relative position in meters eastward
=
=
PosX =
PosY =
N
SF
180
))((
0

+
MSLN
HeightLR
E
SF
)cos(
180
))((
00
LHeightLR
MSLE
+

N
SFLL − )(
0
E
SF− )(
0
