A surveyor has collected GPS points in a narrow canyon with heavy vegetation, processing shows high dilution of precision. What is the most likely cause of the error?

A surveyor has collected GPS points in a narrow canyon with heavy vegetation, processing shows high dilution of precision. What is the most likely cause of the error?

• A. satellites too close together
• B. equipment calibration
• C. random errors
• D. low quality of coordinates

Answer: (A)

The key idea is that Dilution of Precision (DOP) reflects how the geometric arrangement of visible satellites affects the quality of the GPS solution. When satellites are spread across the sky, their lines of position intersect in ways that give independent, well-conditioned information, leading to higher precision. When the view of the sky is limited—as in a narrow canyon with heavy vegetation—the satellites that can be seen tend to cluster in a small portion of the sky. This close grouping provides less independent information, making the geometry poorly conditioned and increasing potential position errors. That clustered geometry is the simple, direct reason for high DOP. Equipment calibration or random errors can cause other issues, but they don’t specifically explain the geometry-driven increase in uncertainty that DOP measures. Low quality coordinates are a symptom of degraded geometry, not the root cause.

The key idea is that Dilution of Precision (DOP) reflects how the geometric arrangement of visible satellites affects the quality of the GPS solution. When satellites are spread across the sky, their lines of position intersect in ways that give independent, well-conditioned information, leading to higher precision. When the view of the sky is limited—as in a narrow canyon with heavy vegetation—the satellites that can be seen tend to cluster in a small portion of the sky. This close grouping provides less independent information, making the geometry poorly conditioned and increasing potential position errors. That clustered geometry is the simple, direct reason for high DOP.

Equipment calibration or random errors can cause other issues, but they don’t specifically explain the geometry-driven increase in uncertainty that DOP measures. Low quality coordinates are a symptom of degraded geometry, not the root cause.