Which of the following is NOT a characteristic of the Global Positioning System (GPS)?
- AThe Multipath Error occurs when the signal reaches the receiver's antenna via multiple paths.
- BGPS uses the WGS84 ellipsoid as its coordinate reference system.
- CA minimum of three satellites is sufficient to determine a highly accurate 3D position and receiver clock offset.Correct
- DDilution of Precision (DOP) is a measure of the geometric strength of the satellite.
Solution
Concept
GPS Satellite Requirements for 3D Positioning
Formula
N/A
Step-by-step solution
1. Review the requirement for determining a 3D position and receiver clock offset in GPS. 2. Identify that a minimum of four satellites is required for a 3D position, whereas three satellites only give a 2D position. 3. Conclude that Option (c) is an incorrect statement about GPS characteristics and select it as the answer.
Explanation
To determine a precise 3D position (latitude, longitude, and altitude) and correct the receiver's clock error, a minimum of four satellites is required, not three. Three satellites can only provide a 2D position (latitude and longitude). Therefore, statement C is incorrect and is NOT a true characteristic of GPS.
Shortcut
To remember GPS satellite requirements, use the rule "3D = 4 Satellites": - 3 Satellites: 2D Position only (Latitude and Longitude) - 4 Satellites: 3D Position + Clock Offset (Latitude, Longitude, Altitude, and Time)
Common mistake
A common mistake is selecting option C as a correct statement by assuming that three satellites are sufficient for 3D positioning because there are three spatial dimensions (latitude, longitude, and altitude). Students often forget that a fourth satellite is required to solve for the receiver's clock error/offset. Another common error is confusing DOP with signal strength rather than understanding it as a measure of satellite geometric configuration.
Correct answer: C) A minimum of three satellites is sufficient to determine a highly accurate 3D position and receiver clock offset.