Which statement about GPS satellite geometry and positioning accuracy is true?

Which statement about GPS satellite geometry and positioning accuracy is true?

• A. Geometry has no effect on GPS accuracy.
• B. Better satellite geometry improves positioning accuracy.
• C. Geometry affects only timing accuracy.
• D. Geometric dilution of precision is constant regardless of satellite positions.

Answer: (B)

The key idea here is how satellite geometry influences how measurement errors translate into the estimated position. In GPS, you solve for three position coordinates and the receiver’s clock bias using pseudorange measurements from at least four satellites. When those satellites are well spread across the sky, the geometry provides strong independent lines of sight to pin down your location; small errors in the measurements then produce only small errors in the computed position and in the clock bias. If the satellites are clustered together or concentrated near the horizon, the geometry is poor, and the same measurement errors get amplified, leading to larger position errors. This relationship is captured by dilution of precision values: better geometry lowers the dilution and yields more accurate positioning. So the true statement is that better satellite geometry improves positioning accuracy. Geometry does affect more than just timing accuracy, and it is not constant—dilution of precision changes as satellite positions change.

The key idea here is how satellite geometry influences how measurement errors translate into the estimated position. In GPS, you solve for three position coordinates and the receiver’s clock bias using pseudorange measurements from at least four satellites. When those satellites are well spread across the sky, the geometry provides strong independent lines of sight to pin down your location; small errors in the measurements then produce only small errors in the computed position and in the clock bias.

If the satellites are clustered together or concentrated near the horizon, the geometry is poor, and the same measurement errors get amplified, leading to larger position errors. This relationship is captured by dilution of precision values: better geometry lowers the dilution and yields more accurate positioning.

So the true statement is that better satellite geometry improves positioning accuracy. Geometry does affect more than just timing accuracy, and it is not constant—dilution of precision changes as satellite positions change.