Geodesy Review Answers Flashcards
In GPS, distances are measured through satellites orbiting in nearly _______ orbits at nominal altitude of about _________.
a. circular, 21,038 km
Ranges are measured with signals that are broadcast from the satellites to the gps receivers in the ________ part of the _________ spectrum.
b. microwave, electromagnetic
The satellite can mark the moment the signal _______ and the receiver can mark the moment it _______.
c. departs, arrives
From satellites codes are carried to GPS receivers by _____ waves. This waves has at least ______ characteristic such as phase, amplitude, or frequency that may change or modulate to carry information.
b. carrier, one
Are freely available to the public. This code is a 1,023 bit long pseudo-random code broadcast at 1.023 MHz, repeating every millisecond.
a. Coarse / Acquisition code
Reserved for military usage. This is a similar code broadcast at 10.23 MHz, but it repeats only once a week.
c. Restricted Precise code
The P Code provides service for _____. Which is designed for higher positioning accuracy and was originally available only to users authorized by the department of defense.
d. Precise positioning service
What are the GPS frequencies of L1and L2?
c. 1575.42 MHz and 1227.60 MHz
The satellites are equipped with _______ clocks.
atomic
Only needs one frequency standard because its electromagnetic wave travels to a retroprism and is reflected back to its origination
a. EDM ranging
Broadcast signals from satellites are collected by the receiver, not reflected.
c. GPS ranging
What is NAVSTAR GPS?
b. Navigation system with timing and ranging, global positioning system
A method of electronic ranging using pulsed VHF(very-high-frequency) signals, was originally designed for bomber navigation, but was later adapted to more benign uses.
b. SHORAN
By knitting together continental datum’s, ______ might be considered to be the first practical step toward positioning on a truly global scale.
HIRAN
The first earth-orbiting satellite, made that possible.
SPUTNIK
NASA’s first satellite tracking system. A ranging technique useful to GPS
PRIME MINITRACK
The technique is that the recordings are encoded with time tags controlled by hydrogen masers, the most stable oscillators(clocks).
VLBI
Its signal provides enough information to determine the exact moment of its closest approach to the earth.
DOPPLER SHIFT
The first prototype satellite of the immediate precursor of the GPS system that was successfully launched reached orbit on June 29, 1961.
TRANSIT
TRANSIT satellites used the frequencies of ______ and ______, while GPS uses 1575.42 MHz and 1227.60 MHz.
400 MHz and 150 MHz
GPS needed at least ______ satellite above an observer’s horizon for adequate positioning, it has to be satisfied at all times anywhere on or near the earth.
Four
The ________ allowed the GPS receiver to acquire signals from several satellites simultaneously and still distinguish them from one another.
PRN Codes
When an observer actually performs a GPS survey project, one of the most noticeable aspects of a satellite’s motion is that it returns to the same position in the sky about _____________ each day.
4 minutes earlier
The satellite actually ________________ with each successive solar day.
lose 3 minutes and 56 seconds
The accuracy of a GPS position is subject to a geometric phenomenon called dilution of precision(DOP). A low DOP factor is _____, a high DOP factor is _____.
good, bad
11 GPS satellites launched from Vanderberg Air Force between 1978 and 1985 were known _______.
BLOCK I satellites
