gps Flashcards
meaning of gps
global positioning system
GPS was originally
developed for military use
by US Army and employed
for civilian use since
1990s
parts of gps
space segment
b) control segment
c) user segment
- consists nominally of 24 satellites operating in six orbital
planes spaced at 60° intervals around the equator
space segment
- These satellites are the ones that transmit signals from
space, based on which times and position of a user are
measured.
space segment
Satellites have a mean altitude of 20,200 km above the
Earth
space segment
consists of monitoring stations which monitor the signals and track the positions of the satellites over time. The tracking information is relayed to the ______that uses this data to make precise, near-future predictions of the satellite orbits, and their clock correction parameters.
control segment
master control station
consists of GPS receivers
c) user segment
These receivers track 4 or more GPS satellites and
compute their own position. ( A minimum of 4 satellites
are required to determine the position X,Y,Z and time)
c) user segment
The Pros of GPS for Land
Surveying
- It offers a higher level of accuracy than
conventional surveying methods - Calculations are made very quickly and
with a high degree of accuracy - GPS technology is not bound by
constraints such as visibility between
stations - Land surveyors can carry GPS components
easily for fast, accurate data collection - Some GPS systems can communicate
wireless for real-time data delivery
TheCons of GPS for Land
Surveying
GPS land surveying equipment requires a
clear view of the sky to receive satellite
signal
- Interference from dense foliage and other
structures can limit function and
communication - All GPS survey equipment is subject to
failure from dead batteries and system
malfunction - Special equipment may be required and
can be costly
THE GPS SIGNAL
L1 signal
L2 signal
L1 signal value
- 1575.42 MHz (154 x 𝑓0)
L2 signal value
1227.60 MHz (120 x 𝑓0)
𝑓0
10.23 MHz.
