Glossary
Appendix B
GSR2600
101
the effects of the ionosphere removed. It provides a different
ambiguity value (non-integer) than a simple measurement on
that frequency.
Ionosphere -
The layers of ionized air in the atmosphere
extending from 70 kilometers to 700 kilometers and higher.
Depending on frequency, the ionosphere can either block radio
signals completely or change the propagation speed. GPS
signals penetrate the ionosphere but are delayed. This delay
induces error in the GPS measurements that can result in poor
survey results. Most GPS receivers/processing software model
the ionosphere to minimize its affects. Also, the effects of
ionosphere can be nearly eliminated by using dual frequency
receivers which can calculate the delay due to ionosphere.
Ionospheric delay -
A wave propagating through the
ionosphere [which is a non-homogeneous (in space and time)
and dispersive medium] experiences delay. Phase delay
depends on electron content and affects carrier signals. Group
delay depends on dispersion in the ionosphere as well and
affects signal modulation (codes). The phase and group delay
are of the same magnitude but opposite sign.
Kinematic -
The user’s GPS antenna is moving. In GPS, this
term is typically used with precise carrier phase positioning, and
the term dynamic is used with pseudorange positioning.
Kinematic surveying -
A form of continuous differential
carrier-phase surveying requiring only short periods of data
observations. Operational constraints include starting from or
determining a known baseline and tracking a minimum of four
satellites. One receiver is statically located at a control point,
while others are moved between points to be measured.
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.
750-1-0093 Rev 1.book Page 101 Friday, June 28, 2002 4:02 PM
