Which one of the following statements with respect to Global Positioning System (GPS) is not correct?
- (a)It is based on network of satellites orbiting above the Earth.
- (b)It is based on the system of triangulation.
- (c)GPS receivers provide location in terms of latitude, longitude and altitude.
- (d)It provides information exclusively for military operations.
Correct — D, 'It provides information exclusively for military operations.' This is the incorrect statement. Although GPS was developed by the US military, it is freely available for civilian use worldwide — navigation, mapping, surveying, aviation, agriculture and even bank and power-grid time-stamping. The other three statements are true, so the exception the question asks for is D.
- (a)It is based on network of satellites orbiting above the Earth. — This is true — GPS relies on a constellation of about two dozen satellites orbiting the Earth, so it is a correct statement, not the exception.
- (b)It is based on the system of triangulation. — This is true in the sense the exam intends — a GPS receiver fixes its position from its distances to several satellites, so the statement is correct.
- (c)GPS receivers provide location in terms of latitude, longitude and altitude. — This is true — GPS gives a three-dimensional fix (latitude, longitude and altitude), so it is a correct statement and not the odd one out.
The Global Positioning System is a satellite-based navigation system run by the United States. A receiver picks up signals from at least four satellites and computes its distance to each, then works out its precise three-dimensional position and the time. It is dual-use: built for defence, but open to civilians everywhere.
The question is a 'which is NOT correct' item. Three statements are standard, accurate facts about GPS. The false one over-claims that GPS is only for the military, ignoring its enormous civilian role — that over-statement is the trap and the answer.
- GPS is a US satellite-navigation system using a constellation of satellites.
- A receiver fixes its position from distances to multiple satellites.
- It reports latitude, longitude and altitude (a 3-D fix) plus precise time.
- GPS is dual-use — widely used by civilians, not exclusively by the military.
- Assuming GPS is used only by the military because it was built for defence.
- Overlooking that the question asks for the statement that is NOT correct.
A 'which statement is not correct' test on the basics of GPS.
In which of the following areas can GPS technology be used? 1. Mobile phone operations 2. Banking operations 3. Controlling the power grids. Select the correct answer using the code given below:
- (a) 1 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer(d) 1, 2 and 3
Same concept — the reach of GPS. That UPSC item shows GPS is used in mobile phones, banking and power grids (i.e. far beyond the military); this one asks you to reject the claim that GPS is 'exclusively' military.
- practice — not a real PYQ
India's own regional satellite navigation system is known as
- (a)GLONASS
- (b)Galileo
- (c)NavIC (IRNSS)
- (d)BeiDou
Answer(c) NavIC (IRNSS) — India's regional navigation satellite system.
- practice — not a real PYQ
A GPS receiver typically needs signals from a minimum of how many satellites to fix a 3-D position?
- (a)1
- (b)2
- (c)3
- (d)4
Answer(d) 4 — four satellites are needed for a three-dimensional position and time fix.