LAB 4. CONTOURS, PROFILES AND SLOPES

1. Calculate the average gradient from point A to point B on the following map. Express the gradient as:

Point B

Point A

a. feet per mile

Map distance A-B = 3 inches; actual distance = 3 x 24,000 inches = 72,000 inches =1.14 miles.

Elevation change = 636 - 594 = 42 feet.

Gradient = 42 feet per 1.14 miles = 36.8 feet per mile.

b. a ratio

36.8 feet per 1 mile = 36.8 feet per 5280 feet = 1: 143 (rounded to nearest whole number)

c. an angle (note: Tan X = rise/run; therefore, X = rise/run INV TAN).

Rise /Run = 1/143, 1/143 INV TAN = 0.4 degrees (24 minutes).

2. Construct a topographic profile across Williamsville from the 5000' spot height at 123456 to the 6600' contour at 333777. Use a horizontal scale of 1:24,000 and a vertical scale of 1:2,400.

See below: