FREE NCEES Fundamentals of Surveying Questions and Answers

Question 1

Multi-path errors are most likely to occur in a receiver in which of the following locations?

Accepted Answer

Urban area with numerous tall buildings

Answer

Explanation:
Multi-path errors in GPS occur when satellite signals are reflected off surfaces such as buildings, terrain, or other obstacles before reaching the receiver antenna. In urban areas with tall buildings, there are many surfaces from which signals can reflect, causing the receiver to receive multiple versions of the same signal with slight delays. This can lead to inaccuracies in determining the receiver's position.

Question 2

Assuming the speed of light to be 186,000 mi/sec and a signal transit time of 92ms, what is the approximate distance from the GPS satellite to the receiver?

Accepted Answer

17k mi

Answer

Explanation:
To determine the distance 𝑑 from the GPS satellite to the receiver, we use the formula:
𝑑 = Speed of light × Signal transit time

Given:
*Speed of light = 186,000 miles per second
*Signal transit time = 92 milliseconds = 0.092 seconds (since 1 millisecond = 0.001 seconds)

Calculate the distance:
𝑑 = 186,000mi/sec × 0.092sec
𝑑 ≈ 17,112 miles

Rounded to the nearest thousand miles, the approximate distance from the GPS satellite to the receiver is 17,000 miles. This calculation illustrates how GPS determines distances based on the time it takes for signals to travel from satellites to receivers, using the speed of light as a constant factor.

Question 3

Using GPS, a point's ellipsoidal elevation is determined to be 592.8 ft. From the GEOID03 model, the geoid separation for that point is -139.4 ft. What is the Orthometric height above the geoid at that point?

Accepted Answer

732 ft

Answer

Explanation:
To find the Orthometric height (H) above the geoid at a given point, we use the formula:
H = Ellipsoidal height − Geoid separation

Given:
*Ellipsoidal elevation = 592.8 ft
*Geoid separation = -139.4 ft (negative indicates below the ellipsoid)

Calculate the Orthometric height:
H = 592.8 ft − (−139.4 ft)
H = 592.8 ft + 139.4 ft
H = 732.2 ft

Rounding to the nearest whole number, the Orthometric height above the geoid at that point is approximately 732 ft.

Question 4

Which of the following conditions would be expected with an increasing value for PDOP?

Accepted Answer

A decrease in positional accuracy

Answer

Explanation:
Position Dilution of Precision (PDOP) is a measure of the geometric strength of satellite configurations used to determine a GPS receiver's position. A higher PDOP value indicates poorer satellite geometry, which leads to decreased positional accuracy. Therefore, A decrease in positional accuracy is correct because higher PDOP values result in poorer satellite geometry, leading to decreased accuracy in determining the receiver's position.

Question 5

The most suitable elevation masks for differential GPS surveys are:

Accepted Answer

10 degrees at the base and 15 at the subordinate station

Answer

Explanation:
Elevation masks in GPS refer to the minimum angle above the horizon at which satellites are considered for use in position calculations. Differential GPS (DGPS) surveys typically require higher elevation masks to ensure accuracy and reliability of positioning. The base station and the subordinate station (or rover) may have different elevation mask settings depending on their roles and the survey conditions. Therefore, the correct answer is 10 degrees at the base and 15 degrees at the subordinate station, providing adequate satellite visibility and geometric strength for differential GPS surveys, thereby enhancing the accuracy and reliability of survey measurements.

NCEES National Council of Examiners for Engineering and Surveying Practice Practice Test

NCEES National Council of Examiners for Engineering and Surveying Practice Practice Test

FREE NCEES Fundamentals of Surveying Questions and Answers