Leica Geosystems GPS Basics - Manual (Page 54)

54
GPS Basics -1.0.0en Glossary
L-band
The radio frequency band extending from
390 MHz to 1550 MHz. The frequencies
of the L1 and L2 carriers transmitted by
GPS satellites lie within this L-band.
Least squares estimation
The process of estimating unknown
parameters by minimizing the sum of the
squares of measurement residuals.
Local Ellipsoid
An Ellipsoid that has been defined for
and fits a specific portion of the earth.
Local ellipsoids usually fit single or
groups of countries.
Local Time
Local time equals to GMT time + time
zone.
Longitude
Longitude is the angle between the
meridian ellipse which passes through
Greenwich and the meridian ellipse
containing the point in question. Thus,
Latitude is 0° at Greenwich and then
measured either eastward through 360°
or eastward 180° and westward 180°.
Meridian
An imaginary line joining north to south
pole and passing through the equator at
90°.
Multipath error
A positioning error resulting from
interference between radio waves which
have travelled between the transmitter
and the receiver by two paths of different
electrical lengths.
NAVSTAR
Acronym for Navigation System with
Time and Ranging, the original name for
GPS.
NMEA
National Marine Electronics Association.
Defined a standard (NMEA 0183) to
enable marine electronics instruments,
communication and navigation equip-
ment to communicate. This standard is
used to get time and position data out of
GPS instruments in many applications.
Observing Session
A period of time over which GPS data is
collected simultaneously by two or more
receivers.
Orthometric height
The distance of a point above the geoid
measured along the plumb line through
the point (height above mean sea level).
See also Elevation.