Sokkia RADIAN IS, Operation Manual

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Glossary
RADIAN™IS 59
L1 - The 1575.42 MHz GPS carrier frequency, which contains the
course acquisition (C/A) code, as well as encrypted P-code, and
navigation, messages used by commercial GPS receivers.
L2 - A secondary GPS carrier, containing only encrypted P-code,
used primarily to calculate signal delays caused by the
ionosphere. The L2 frequency is 1227.60 MHz.
Mask Angle - see elevation mask angle.
Multipath - The reception of a satellite signal both along a direct
path and along one or more reflected paths. The reflected signals
are caused by reflecting surfaces near the GPS antenna. The
resulting signal generates an incorrect pseudorange
measurement. Multipath Errors are GPS positioning errors
caused by the interaction of the GPS satellite signal and its
reflections.
NMEA - National Marine Electronics Association, an
organization that created industry standard ASCII log types that
are used by all receivers.
Obstruction - Physical feature that blocks the satellite direct line
of site from the point of observation. GPS signals are very weak.
They can be blocked from reaching the GPS antenna by objects
between the antenna and the satellites. Classic examples of
obstructions are trees and buildings.
Occupation - The period of recorded data for a site. For
example, a 1-hour period of data collection on a survey point is
considered an occupation. Occupation is usually
interchangeable with the term observation.
Orthometric elevation (orthometric height) - The height of a
point above the geoid. Orthometric elevation is often equated
with mean-sea-level elevation.
P-Code (precise or protected) - The protected or precise code
used on both LI and L2 GPS beacons. This code will be made
available by the DOD only to authorized users. The P code is a
very long (about 1014 bits) sequence of pseudo-random binary
biphase modulations on the GPS carrier at a chipping rate of
10.23 MHz which does not repeat itself for about 38 weeks. Each
satellite uses a one-week segment of this code which is unique to
each GPS satellite, and is reset each week.