PS Topographic & Contour Mapping 2 — Questions and Answers
Question 1: A contour line crosses a stream valley in what characteristic shape?
- V-shape pointing upstream (Correct answer)
- U-shape opening downstream
- Straight line across the valley
- Circular closed loop
Correct answer: V-shape pointing upstream
Contour lines form V-shapes that point upstream (uphill) when crossing stream valleys because the stream cuts downward into the terrain.
Question 2: On a topographic map, contour lines that are spaced very close together indicate:
- Gentle slopes
- Steep slopes (Correct answer)
- Flat terrain
- A depression
Correct answer: Steep slopes
Closely spaced contour lines represent steep terrain because the elevation changes rapidly over a short horizontal distance.
Question 3: What is the standard contour interval for a USGS 7.5-minute quadrangle map covering hilly terrain?
- 5 feet
- 10 feet
- 20 feet (Correct answer)
- 40 feet
Correct answer: 20 feet
USGS 7.5-minute quadrangles of hilly terrain typically use a 20-foot contour interval to balance readability and detail.
Question 4: An index contour differs from intermediate contours in that it is:
- Always at sea level
- Drawn with a heavier line and labeled with elevation (Correct answer)
- Dashed instead of solid
- Used only on depression areas
Correct answer: Drawn with a heavier line and labeled with elevation
Index contours are drawn with heavier lines and labeled with their elevation values, typically every fifth contour, to aid map reading.
Question 5: When performing a topographic survey using total station equipment, what does the term 'side shot' refer to?
- A shot taken parallel to the baseline
- A single foresight observation not used as a backsight (Correct answer)
- A check shot to a previously measured point
- A shot taken at 90 degrees to the survey traverse
Correct answer: A single foresight observation not used as a backsight
A side shot is a single observation taken to collect data (such as terrain features) that is not subsequently used as a backsight in the traverse.
Question 6: Which map projection is most commonly used for USGS topographic quadrangle maps in the contiguous United States?
- Mercator
- Lambert Conformal Conic
- Transverse Mercator (UTM) (Correct answer)
- Albers Equal Area
Correct answer: Transverse Mercator (UTM)
USGS 7.5-minute topographic quadrangles use the Transverse Mercator projection as part of the Universal Transverse Mercator (UTM) coordinate system.
Question 7: In topographic surveying, the term 'break line' refers to:
- A line where two contours merge
- A line along which the terrain slope changes abruptly (Correct answer)
- The boundary between survey zones
- A line indicating map sheet limits
Correct answer: A line along which the terrain slope changes abruptly
A break line defines a linear feature along which the terrain surface changes slope abruptly, such as a ridge crest, stream bank, or road edge.
PS Topographic & Contour Mapping 2
A contour line crosses a stream valley in what characteristic shape?