Question

Identify the CORRECT statement(s)

• A. NAVSTAR GPS consists of minimum 24 satellites.
• B. Precision of GPS positioning is being defined by its standard deviation.
• C. DGPS method provides more accurate 3D-position than Relative Static post-processing method.
• D. GPS observations from geodetic GPS receiver provide less accurate position than GPS code receiver.

Hint:

Understanding the different methods of GPS positioning, including DGPS and relative static post-processing, is crucial for achieving the highest levels of accuracy, especially in professional applications like surveying and geodesy.

Answer 1

The Correct Option is A, B

The NAVSTAR GPS system is the global positioning system operated by the United States, and it provides global coverage for location and time services. The system uses a constellation of satellites that communicate with receivers to calculate accurate positions anywhere on Earth.
Analysis of the Statements:
- Option (A) - NAVSTAR GPS consists of minimum 24 satellites: This statement is correct. The NAVSTAR GPS system consists of a minimum of 24 satellites, although there are typically more in operation. This constellation ensures that at least four satellites are visible from any point on Earth at any given time, which is necessary for accurate positioning. The 24 satellites are spread across six orbital planes, providing complete global coverage.
- Option (B) - Precision of GPS positioning is being defined by its standard deviation: This statement is also correct. The precision of GPS positioning refers to the accuracy of the estimated position compared to the true position, and it is often quantified by the standard deviation of the position estimates. A smaller standard deviation indicates higher precision. The precision is influenced by factors like satellite geometry, atmospheric conditions, and multipath effects.
- Option (C) - DGPS method provides more accurate 3D-position than Relative Static post-processing method: This statement is true. DGPS (Differential GPS) uses ground-based reference stations to correct GPS signals, which helps to reduce errors and improve positioning accuracy. It provides more accurate 3D positioning compared to Relative Static post-processing methods, where positions are determined by comparing measurements from two or more fixed locations over time. DGPS can provide real-time corrections, which improves accuracy immediately.
- Option (D) - GPS observations from geodetic GPS receiver provide less accurate position than GPS code receiver: This statement is incorrect. Geodetic GPS receivers are highly accurate and are specifically designed for precise surveying and geodesy. They use carrier-phase measurements, which offer much higher accuracy than the code measurements used by standard GPS receivers. In contrast, standard GPS code receivers are used for general navigation and have lower accuracy. Therefore, the statement is false.
Thus, the correct answers are (A), (B), and (C). These statements are true based on the functioning of the GPS and DGPS systems.