Construction and Topographic Surveys Flashcards

Which of the following statements is a fundamental characteristic of contour lines on a topographic map?

Answer: Closely spaced contours indicate a steep slope.

Contour lines represent lines of equal elevation. When they are close together, it signifies a rapid change in elevation over a short horizontal distance, which defines a steep slope. Conversely, widely spaced contours indicate a gentle slope.

During slope staking for a roadway cut, the point where the designed side slope intersects the natural ground surface is located and staked. This critical point is known as the:

Answer: Catch point

The catch point, also known as a daylight point in cut situations, is the specific location where the planned cut or fill slope intersects the existing ground surface. It marks the outer limit of the required earthwork.

A surveyor needs to calculate the volume of earthwork between two parallel cross-sections. The area of the first cross-section (A1) is 450 sq ft and the area of the second cross-section (A2) is 550 sq ft. The distance (L) between the sections is 100 ft. Which of the following formulas is most commonly used for this calculation and what is the resulting volume?

Answer: Average End Area Formula, resulting in 50,000 cubic feet

The Average End Area Formula is a widely used and straightforward method for estimating earthwork volumes. It calculates the average area of the two end sections and multiplies it by the distance between them. The calculation is V = L * (A1 + A2) / 2 = 100 ft * (450 sq ft + 550 sq ft) / 2 = 50,000 cubic feet.

A contractor has just completed the installation of underground utilities for a new subdivision. Before the trenches are backfilled, the project engineer requests a survey to document the final horizontal and vertical locations of the pipes and structures. This type of survey is best known as:

Answer: An as-built survey

An as-built survey (or record survey) is performed during or after construction to document the final location and elevation of constructed features. For underground utilities, this is critical for future maintenance, avoiding conflicts, and verifying conformance with design plans before the features are buried.

In digital terrain modeling, which of the following is a key advantage of a Triangulated Irregular Network (TIN) over a raster-based Digital Elevation Model (DEM)?

Answer: TINs can more efficiently and accurately represent significant linear features like ridges and breaklines.

A TIN is a vector-based data structure composed of nodes and non-overlapping triangles. Its primary advantage is the ability to vary the density of points, concentrating them in areas of high relief and incorporating distinct breaklines (like ridges, streams, or road edges) for a more precise representation of the terrain surface compared to the fixed grid of a DEM.

A surveyor is setting up control for a building foundation. After staking the building corners, the surveyor erects wooden frames set back from the building lines, upon which strings can be stretched to define the exact wall locations and elevations. These frames are known as:

Answer: Batter boards

Batter boards are temporary wooden frames erected just outside the excavation area. They are used to hold strings or wires that mark the precise horizontal lines and vertical grades of the foundation walls, providing a durable reference that will not be disturbed during construction activities.