PS Map Projections & Cartography Flashcards

What type of map projection is used by USGS 7.5-minute quadrangle maps?

Answer: Transverse Mercator (NAD 83)

Modern USGS 7.5-minute quadrangle maps use the Transverse Mercator projection referenced to NAD 83.

When converting ground coordinates to State Plane coordinates, which factor accounts for the difference in elevation between the survey and the reference ellipsoid?

Answer: Elevation (sea-level) factor

The elevation factor (also called sea-level factor) reduces ground distances to the ellipsoid by dividing by the ratio of the earth's radius to the mean radius plus the elevation.

What does a contour interval of 5 feet mean on a topographic map?

Answer: Each contour line represents a 5-foot change in elevation

The contour interval is the vertical difference in elevation between adjacent contour lines; a 5-foot interval means consecutive lines differ by 5 feet in elevation.

What is the map grid used for military and emergency services navigation in the United States, based on the UTM coordinate system?

Answer: Both MGRS and USNG

Both MGRS and USNG (US National Grid) are alpha-numeric grid systems based on UTM, with MGRS used by the military and USNG adopted for civilian emergency services.

Which property does an equal-area (equivalent) map projection preserve?

Answer: The area of features relative to each other

Equal-area projections maintain correct relative areas across the map, though they distort angles and shapes.

On a standard topographic map, contour lines that are closely spaced together indicate:

Answer: A steep slope

Closely spaced contour lines indicate a rapid change in elevation over a short horizontal distance, meaning the terrain is steeply sloped.