Leveling & Differential Leveling Flashcards
6 cards from real FUNDAMENTAL SURVEYING practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Leveling & Differential Leveling flashcards as text
What is 'trigonometric leveling'?
Answer: Computing elevation differences from measured slope distances and vertical angles
Trigonometric leveling calculates elevation differences using V = S times sin(vertical angle), where S is the slope distance.
Which datum is used as the standard vertical datum in the United States?
Answer: NAVD 88
NAVD 88 (North American Vertical Datum of 1988) is the current official vertical datum for the US, replacing the older NGVD 29.
A Philadelphia rod reads 4.756 ft but is not perfectly plumb. The reading will be:
Answer: Too large
A tilted rod appears longer in the line of sight than a plumb rod, so the reading will be erroneously large.
What is the purpose of the 'peg test' (two-peg test) for a level instrument?
Answer: To detect and measure collimation error in the line of sight
The two-peg test determines whether the instrument's line of sight is truly horizontal by comparing readings at equal and unequal distances.
In barometric leveling, what relationship is used to estimate elevation?
Answer: The decrease in atmospheric pressure with increasing altitude
Barometric leveling exploits the fact that atmospheric pressure decreases predictably with altitude, allowing elevation differences to be estimated from pressure readings.
A level circuit has a total length of 4 miles and a closure error of 0.06 ft. What is the total distance in feet?
Answer: 21,120 ft
Total distance = 4 miles times 5,280 ft/mile = 21,120 ft, giving a precision of 1:352,000.