Q Q5: How GPS works: which of the following statements is FALSE? The GPS system
ID: 1713097 • Letter: Q
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Q5: How GPS works: which of the following statements is FALSE? The GPS system works by timing how long it takes a radio signal to reach a receiver from a satellite and then calculating the distance from that time A. B. With range measurement from enough number of satellites, together with the location of the satellites, it is sufficient to solve four unknowns: three coordinates and the receiver clock bias Each satellite transmits signal on two L-band carrier frequencies, called L1 at1575.42Mhz and L2 at 1227.6Mhz. LI is modulated by two signals, P code and the Navigation message. L2 is modulated by three signals, plus the C/A code Each receiver has a C/A code generator which generates PRN codes exactly same as the one SVs transmitted. It is used to pick up the same PRN signal transmitted by a SV and to C. D. measure the time lag between them E. RTK is carrier-phase based, and reference receiver must be located at a point of known position Q 6: GPS Observables: which of the following statements is FALSE? A receiver tags received signal with the time of its internal clock to create a "pseudo range" (range plus an unknown clock error). The term pseudo range is applied to indicate that the range measured by a receiver includes the clocks' bias A. B. Pseudo range measurements are in meters, with low accuracy but absolute measures C. Carrier phase measurements are in cycles and very accurate, but have initial integer ambiguity Cycle slip is caused by signal lose of lock, and then the initial integer ambiguity does not change D. E. GPS receivers can record many observables, including pseudo range measurements C/A, P1, P2; phase measurements L1, L2 and Doppler phase measurements D1 and D2 Q7: Acronyms: referring to the lecture notes, which of the following answers is WRONG? A. RTCM (Radio Technical Commission for Maritime) B. RTK (Real Time Kinematic) C. RINEX (Receiver Independent Exchange Standard) D. WADGPS (Wide Area DGPS Systems) E. CORS (Continuously Operating Reference Satellite) Q8: GPS surveying: referring to the lecture notes, which of the following answers is NOT a GPS surveying method? A. Phase-smoothed DGPS surveying B. Static or rapid static surveying C. Reoccupation surveying D. Stop and go surveying E. RTK on-the-fly surveyingExplanation / Answer
5.D is false
Explaination: Pseudorandom noise (PRN) codes are an important element of code division multiple access (CDMA) based satellite navigation systems. Each satellite within a GNSS constellation has a unique PRN code that it transmits as part of the C/A navigation message. This code allows any receiver to identify exactly which satellite(s) it is receiving.
6.A
Cycle Slip – A cycle slip is a discontinuity in GPS carrier phase observations caused by signal loss, usually due to obstructions. If a GPS receiver loses a signal temporarily, when the signal is reacquired there may be a jump in integer number of full carrier phase cycles (ambiguity).
7.none is wrong
Every options are correct.
RINEX:Receiver Independent Exchange Format (RINEX) is a data interchange format for raw satellite navigation system data.
CORS:Continuously Operating Reference Station (CORS)
8.E
RTK on the fly surveying: It is done by using drones,not by gps methods.
some confusion options gets explained above.
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