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Question 1
ప్రశ్న 1
A surveyor operates ONE GNSS receiver and computes a position directly from satellite broadcast navigation data, without reference-station observations or differential corrections. Which positioning method is being used?
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Explanation:
Standalone positioning uses observations made by the individual receiver and the available satellite navigation information. It does not require simultaneous measurements from a nearby reference receiver. The solution normally estimates the receiver coordinates and receiver-clock bias. Atmospheric effects, multipath, satellite geometry and other errors may limit its accuracy. It should not automatically be assumed suitable for centimetre-level engineering control. A project requiring higher accuracy may need differential or other appropriately validated methods.
వివరణ:
Question 2
ప్రశ్న 2
What is the fundamental idea of DIFFERENTIAL GNSS (DGNSS) using a reference station whose coordinates are accurately known?
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Explanation:
The reference station has a known position, allowing predicted satellite-to-reference geometric ranges to be calculated. Differences between predicted and observed ranges contain information about measurement errors and biases. Suitable corrections can be transmitted or applied to a rover observing common satellites. Errors that are sufficiently similar at the two sites can be reduced through differential processing. Local multipath at the rover is generally not removed by a distant base correction. The effectiveness of the method depends on reference quality, baseline separation and observation conditions.
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Question 3
ప్రశ్న 3
In RELATIVE GNSS surveying, what is the primary quantity determined between a reference receiver and a rover from suitably processed common-satellite observations?
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Explanation:
Relative GNSS surveying uses observations from two or more receivers to establish their coordinate differences. The baseline vector contains components in a specified three-dimensional coordinate system. Suitable processing of common-satellite observations helps reduce shared error effects. A known reference-station coordinate allows the baseline vector to be converted into a rover position in the same reference frame. If the reference coordinates are wrong, rover coordinates derived from that reference can inherit a systematic shift. A baseline solution is therefore not independent of the reliability of its control.
వివరణ:
Question 4
ప్రశ్న 4
A water-supply project requires precise control coordinates for a stable monument. A dual-frequency GNSS antenna remains stationary on the monument during a sufficiently long observation session, and the recorded data are processed with reference-station observations afterwards. Which method best describes this work?
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Explanation:
In static GNSS surveying, receivers remain at fixed stations during their observation sessions. Measurements are recorded over a suitable period while satellites change position in the sky. Post-processing combines the survey observations with suitable reference data. Observation duration and accuracy depend on the intended survey standard and local conditions. Static methods are widely used for establishing reliable control networks when properly planned and checked. The stationary occupation distinguishes this case from rover-based kinematic point collection.
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Question 5
ప్రశ్న 5
Which statement correctly distinguishes RAPID-STATIC GNSS surveying from a conventional longer STATIC GNSS session?
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Explanation:
Rapid-static GNSS still observes a station while the antenna remains stationary. It is designed to use shorter occupation periods than many conventional static surveys. Carrier-phase measurements and ambiguity resolution are important for precise rapid-static baseline estimation. Its feasibility depends on baseline length, constellation availability, signal quality and the processing strategy. Short sessions are not guaranteed to meet every control accuracy requirement. Observation duration should be selected from applicable specifications and verified field results.
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Question 6
ప్రశ్న 6
A GNSS base receiver is set over a known survey point and broadcasts suitable observations or corrections to a moving rover. The rover processes carrier-phase data and produces near-real-time positions. Which technique is being described?
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Explanation:
RTK uses a reference source and a rover to compute relative GNSS positions in near real time. The receiver processes code and typically carrier-phase observations. Correct reference coordinates and reliable data communication are important for obtaining valid results. Resolving carrier-phase ambiguities supports precise relative positioning. Satellite obstructions, multipath or communication interruptions may degrade the solution. Independent known-point checks remain necessary for important engineering setting out.
వివరణ:
Question 7
ప్రశ్న 7
A survey team records GNSS data simultaneously at a base and a moving rover but has NO reliable live correction link. The observations will be combined later in office software to determine the rover trajectory. Which method is most appropriate?
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Explanation:
PPK uses stored GNSS observations collected by the reference receiver and the rover. Their observations are processed after the field session to determine relative positions. A live correction link is not required while recording the data. The method still depends on usable common observations, valid reference information and appropriate carrier-phase processing. It does not permit the observer to rely on final corrected coordinates immediately during the field session. It can be useful when communication for real-time corrections is unreliable.
వివరణ:
Question 8
ప్రశ్న 8
In an ideal RTK setup, the computed rover EASTING equals the entered base EASTING plus the correctly determined base-to-rover easting difference. The base's true easting is 5000.000 m, but the operator enters 5000.400 m. Assuming the computed relative baseline is otherwise exact and no transformation is applied, how is the computed rover EASTING affected?
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Explanation:
The relative easting difference is assumed to be correct. The rover coordinate is formed by adding that difference to the entered base coordinate. Entering the base easting 0.400 m too large therefore makes the derived rover easting 0.400 m too large. Easting increases toward the east in the stated grid. The corresponding systematic displacement is consequently 0.400 m east. A convincing RTK fixed solution cannot independently validate an incorrectly entered base coordinate.
వివరణ:
Question 9
ప్రశ్న 9
Compared with CODE PSEUDORANGE observations, which feature makes GNSS CARRIER-PHASE observations useful for precise relative surveying but introduces an additional processing challenge?
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Explanation:
Carrier-phase observations track the phase of the received radio carrier. They can provide substantially finer measurement precision than ordinary code pseudoranges. However, the receiver initially does not know the complete integer number of carrier wavelengths between the satellite and antenna. This is referred to as the carrier-phase ambiguity. Reliable ambiguity determination is important for precise relative positioning. Carrier measurements can still be affected by multipath, signal interruption and other errors.
వివరణ:
Question 10
ప్రశ్న 10
A rover display changes its RTK ambiguity status from FLOAT to FIXED. Which interpretation is the most technically defensible?
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Explanation:
A float solution estimates carrier-phase ambiguities without committing them to integers. A fixed solution uses ambiguities that the processing algorithm has resolved to integer values. Successful ambiguity fixing often improves relative positioning precision. An incorrect fix can nevertheless occur under poor observations or unsuitable geometry. Errors in base coordinates, antenna heights and the adopted datum may also remain. Therefore fixed status alone is not sufficient proof that an engineering position meets tolerance.
వివరణ:
Question 11
ప్రశ్న 11
For an idealised SAME-SATELLITE, SAME-EPOCH DGNSS correction, a known base has a calculated reference range of 20,200,000.0 m but observes a code pseudorange of 20,200,004.0 m. The base supplies an additive correction equal to CALCULATED MINUS OBSERVED range. A rover observes an uncorrected pseudorange of 20,200,055.0 m to that satellite. Assuming this correction is applicable and ignoring other residuals, what is the corrected rover pseudorange?
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Explanation:
The reference station compares its calculated range with the observed pseudorange. The signed correction is 20,200,000.0 - 20,200,004.0 = -4.0 m. Under the explicitly stated additive-correction convention, the rover adds -4.0 m to its observation. Therefore its corrected pseudorange is 20,200,055.0 - 4.0 = 20,200,051.0 m. The calculation concerns one satellite range rather than a complete rover position. Real differential processing also accounts for receiver clocks and remaining atmospheric or local error effects.
వివరణ:
Question 12
ప్రశ్న 12
A GNSS reference station has projected grid coordinates N = 1000.000 m and E = 2000.000 m. A correctly transformed relative GNSS baseline gives the rover's horizontal components FROM BASE TO ROVER as delta N = +120.000 m and delta E = -50.000 m. What are the rover grid coordinates?
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Explanation:
The base-to-rover vector is explicitly stated in the same projected grid axes as the base coordinates. A positive northing difference means the rover lies north of the base. A negative easting difference means the rover lies west of the base. The rover northing is 1000.000 + 120.000 = 1120.000 m. Its easting is 2000.000 - 50.000 = 1950.000 m. No latitude-longitude transformation is needed because the vector has already been supplied in the grid coordinate system.
వివరణ:
Question 13
ప్రశ్న 13
Repeated RTK observations at a site agree with one another within 0.010 m, but an independent reliable control check reveals that the results are consistently displaced about 0.500 m east because the base coordinates were entered incorrectly. Which conclusion is correct?
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Explanation:
Precision describes the closeness of repeated measurements to one another. Accuracy concerns agreement with the accepted reference or true value. Observations clustered within 0.010 m demonstrate good repeatability in this example. Their common 0.500 m displacement shows a substantial systematic error relative to control. Repetition alone may not detect a shared base-coordinate or datum mistake. An independent check on known control is therefore essential in engineering surveying.
వివరణ:
Question 14
ప్రశ్న 14
Two GNSS observation windows have similar range-observation quality and the SAME number of tracked satellites. Window I has PDOP = 6.0 and Window II has PDOP = 2.0. Which statement best interprets these figures?
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Explanation:
PDOP is a dimensionless indicator of three-dimensional satellite geometry. Lower PDOP generally means a stronger geometric arrangement for position estimation. With comparable range errors, PDOP of 2.0 is more favourable than PDOP of 6.0. This does not guarantee a particular absolute positioning error for either window. Multipath, obstruction, incorrect reference coordinates and processing problems may still dominate. Satellite-count comparisons should therefore be supplemented by geometry and signal-quality checks.
వివరణ:
Question 15
ప్రశ్న 15
A GNSS check point has observed coordinate errors relative to accepted grid control of +0.120 m in NORTHING and -0.050 m in EASTING. What is the magnitude of its horizontal positional discrepancy, assuming plane coordinates?
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Explanation:
The northing and easting discrepancies are perpendicular components of the horizontal error vector. The magnitude is found using the Pythagorean relationship. Therefore e = sqrt[(0.120)^2 + (-0.050)^2] m. This becomes sqrt(0.0144 + 0.0025) = sqrt(0.0169). The resulting horizontal discrepancy is 0.130 m. The negative sign of the easting error determines its direction but does not reduce its contribution to the magnitude.
వివరణ:
Question 16
ప్రశ్న 16
A manufacturer states an illustrative RTK HORIZONTAL accuracy expression of ±(8 mm + 1 ppm of BASELINE LENGTH), under specified operating conditions. For a base-to-rover baseline of 2.000 km, what is the numerical magnitude of this expression?
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Explanation:
The stated formula combines a fixed term of 8 mm with a baseline-proportional term. One part per million of one kilometre is one millimetre. At 2.000 km, the 1 ppm contribution is therefore 2 mm. Adding the two terms gives 8 + 2 = 10 mm. Hence the stated accuracy expression evaluates to ±10 mm under its specified conditions. This is an interpretation of the supplied model, not a guarantee that every real-world observation is within 10 mm.
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Question 17
ప్రశ్న 17
Why can observing compatible GNSS signals at TWO frequencies help reduce a major propagation error in surveying?
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Explanation:
The ionosphere is a dispersive propagation medium for GNSS radio frequencies. Its effect on measured code and carrier signals depends on the transmitted frequency. Compatible dual-frequency observations can therefore be combined to reduce first-order ionospheric error. The neutral-atmosphere delay is not eliminated by the same simple frequency-difference principle. Multipath and poor geometry also remain possible error sources. Dual-frequency tracking is valuable but cannot substitute for appropriate site selection and quality checks.
వివరణ:
Question 18
ప్రశ్న 18
Which statement correctly describes the TROPOSPHERIC contribution to GNSS ranging errors?
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Explanation:
GNSS signals pass through the neutral atmosphere before reaching a ground receiver. Dry gases and atmospheric water vapour influence the signal's propagation time. The resulting tropospheric delay depends on atmospheric conditions and the satellite direction. Processing models and suitable common-mode differencing can reduce its effect. Residual tropospheric errors may increase with baseline separation and differences in local atmospheric conditions. A fixed carrier-phase solution does not guarantee that these residuals are zero.
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Question 19
ప్రశ్న 19
An RTK rover is positioned beside a reflective steel tank and a glass-fronted building. Some satellite signals are received both directly and after reflection from nearby surfaces. What is the principal GNSS error mechanism?
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Explanation:
Multipath occurs when reflected GNSS signals arrive at the receiving antenna alongside direct signals. The reflected components normally follow different path lengths. Their interference can distort the receiver's measured code or carrier phase. Steel structures and glass surfaces can create difficult reflective environments. A base-station correction cannot generally remove local multipath that occurs only at the rover. Moving the antenna to a clearer site and using appropriate quality checks can improve survey reliability.
వివరణ:
Question 20
ప్రశ్న 20
A proposed sewer alignment passes under dense tree canopy and an elevated road where GNSS satellite visibility is intermittent. Which engineering survey strategy is most defensible for accurately locating points in the obstructed section?
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Explanation:
GNSS requires sufficiently strong and suitably distributed satellite signals. Tree canopy and an elevated structure can block signals and introduce multipath. These conditions may prevent reliable RTK or other GNSS positioning at the affected points. Verified control can be established where satellite reception is suitable. A total-station traverse or other appropriate terrestrial method can extend that control through the obstructed corridor. The transferred points should still be checked against the required project accuracy and coordinate reference.
వివరణ:
Question 21
ప్రశ్న 21
What is the principal surveying value of a CONTINUOUSLY OPERATING REFERENCE STATION (CORS) or a suitable network of such stations?
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Explanation:
A CORS is a permanently installed GNSS reference receiver at a carefully determined position. It collects satellite observations over extended periods. Its data can support post-processing and some networks offer real-time correction services. Referencing suitable control stations can help place project results in a recognised coordinate frame. Data quality, communication availability and the stated reference coordinates must still be checked. CORS access does not remove the need for independent project control verification.
వివరణ:
Question 22
ప్రశ్న 22
A rover using a LIVE RTK correction service loses its data connection, and the most recent corrections become increasingly old. Which response best protects the quality of a centimetre-level stakeout?
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Explanation:
RTK processing relies on valid and sufficiently current correction or reference data. When updates stop, the correction information can become stale as satellite and atmospheric conditions change. The rover may lose ambiguity fixing or experience degraded position quality. Its displayed solution status and correction age should therefore be monitored. The link should be restored or an appropriately validated alternative method should be used. Critical stakeout points should not be accepted solely because coordinates remain visible on the controller.
వివరణ:
Question 23
ప్రశ్న 23
What does a CYCLE SLIP mean in GNSS CARRIER-PHASE observation processing?
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Explanation:
A receiver tracks the accumulated phase of incoming carrier signals. Loss of lock or significant signal disturbance can cause the tracked cycle count to jump. Such a discontinuity is termed a cycle slip. It can invalidate the assumed constant carrier-phase ambiguity over the affected interval. Processing must detect and handle the slip before relying on precise phase-based results. Obstructions and poor signal conditions make this issue particularly relevant in engineering GNSS surveys.
వివరణ:
Question 24
ప్రశ్న 24
A static GNSS processing result gives an ELLIPSOIDAL HEIGHT of 105.250 m for the ANTENNA REFERENCE POINT (ARP). The ARP is actually 1.850 m vertically above a survey mark, but the processor subtracts an erroneously entered antenna height of 1.650 m. What is the error in the COMPUTED ellipsoidal height of the ground mark, assuming all other quantities are exact?
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Explanation:
The GNSS result refers to the antenna reference point rather than directly to the ground mark. The correct mark height is 105.250 - 1.850 = 103.400 m. Using the incorrectly entered antenna height gives 105.250 - 1.650 = 103.600 m. The computed mark is therefore 0.200 m too high. A precise GNSS baseline does not itself detect an incorrectly entered antenna height. Field height measurements and the antenna reference definition must be checked carefully.
వివరణ:
Question 25
ప్రశ్న 25
For establishing and setting out water-main appurtenances to a specified project grid, which complete GNSS surveying practice is MOST defensible?
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Explanation:
GNSS method selection must reflect the required positional tolerance and site conditions. Static and post-processed approaches can be useful for control, while validated RTK can support efficient field setout. The coordinate reference frame and relevant transformations must agree with the engineering design. Correct base coordinates, antenna heights and signal quality are essential inputs. Independent control checks help detect systematic errors that repeated GNSS readings may miss. Conventional surveying methods remain useful where satellite observation is obstructed or otherwise unreliable.
వివరణ:
Answer Key సమాధానాల పట్టిక
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Question 1 ప్రశ్న 1Answer: B. Standalone or autonomous GNSS positioning. సమాధానం: B.
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Question 2 ప్రశ్న 2Answer: D. It uses observations at a known reference station to estimate corrections that can reduce errors in a suitably located rover's observations. సమాధానం: D.
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Question 3 ప్రశ్న 3Answer: A. The three-dimensional baseline vector between the two receiver positions. సమాధానం: A.
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Question 4 ప్రశ్న 4Answer: C. Static relative GNSS surveying. సమాధానం: C.
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Question 5 ప్రశ్న 5Answer: B. Rapid-static generally uses a shorter stationary occupation, subject to suitable baseline lengths, satellite geometry and processing conditions. సమాధానం: B.
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Question 6 ప్రశ్న 6Answer: A. Real-time kinematic (RTK) relative GNSS surveying. సమాధానం: A.
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Question 7 ప్రశ్న 7Answer: D. Post-processed kinematic (PPK) GNSS positioning. సమాధానం: D.
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Question 8 ప్రశ్న 8Answer: C. It is 0.400 m too far east. సమాధానం: C.
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Question 9 ప్రశ్న 9Answer: A. Carrier phase provides much finer measurement resolution but contains an initially unknown integer number of complete carrier cycles. సమాధానం: A.
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Question 10 ప్రశ్న 10Answer: B. FIXED means the carrier-phase ambiguities have been resolved to integer values according to the estimator, but independent survey quality checks are still necessary. సమాధానం: B.
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Question 11 ప్రశ్న 11Answer: D. 20,200,051.0 m. సమాధానం: D.
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Question 12 ప్రశ్న 12Answer: C. N = 1120.000 m; E = 1950.000 m. సమాధానం: C.
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Question 13 ప్రశ్న 13Answer: A. The results show good repeatability (precision) but poor absolute accuracy relative to the intended control. సమాధానం: A.
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Question 14 ప్రశ్న 14Answer: B. Window II has better three-dimensional satellite geometry and generally less amplification of ranging errors under comparable conditions. సమాధానం: B.
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Question 15 ప్రశ్న 15Answer: A. 0.130 m. సమాధానం: A.
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Question 16 ప్రశ్న 16Answer: D. ±10 mm. సమాధానం: D.
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Question 17 ప్రశ్న 17Answer: A. The ionospheric effect is frequency dependent, so dual-frequency observations can be combined to reduce its first-order contribution. సమాధానం: A.
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Question 18 ప్రశ్న 18Answer: B. Signal propagation through the neutral atmosphere is delayed by dry gases and water vapour; suitable models and relative observations can reduce this effect. సమాధానం: B.
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Question 19 ప్రశ్న 19Answer: D. Multipath, which can bias or disturb code and carrier-phase measurements even when a correction service is used. సమాధానం: D.
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Question 20 ప్రశ్న 20Answer: C. Establish verified control at suitable open-sky locations and transfer it through the obstructed section using a total station or another suitable conventional survey method. సమాధానం: C.
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Question 21 ప్రశ్న 21Answer: B. It provides continuously collected reference GNSS observations and, where offered, correction services that can support relative or real-time positioning tied to stated reference coordinates. సమాధానం: B.
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Question 22 ప్రశ్న 22Answer: A. Check correction age and solution status, restore or replace the correction link, and verify the solution before accepting further high-accuracy stakeout points. సమాధానం: A.
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Question 23 ప్రశ్న 23Answer: C. A discontinuity in the tracked carrier-phase cycle count, commonly associated with loss or interruption of signal lock. సమాధానం: C.
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Question 24 ప్రశ్న 24Answer: D. The ground mark is computed 0.200 m too high. సమాధానం: D.
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Question 25 ప్రశ్న 25Answer: A. Choose static, RTK or PPK according to tolerance and site conditions; verify the reference frame and base/control coordinates, antenna heights and observation quality; independently check results and use terrestrial methods where GNSS is obstructed. సమాధానం: A.