A topographic map is a map that shows
- Slides: 8
A topographic map is a map that shows the shape (topography) of the land.
Topographic Map Vocabulary • Each contour line represents lines of equal elevation • The space between contour lines is called the contour interval • Every fifth line is called an index contour with the number of feet of elevation • Little lines that intersect contour lines are called “hachures”
Rules for Topographic Maps • Two contour lines never cross each other • Contours make a “V” shape as they cross streams, “v’s” point upstream • The closer the contour lines are, the steeper the slope is • Closed contours (circles inside each other) represent hills • All contour lines close eventually even if it’s off the map • Hachure marks represent depressions
Finding the map’s location on Earth Latitude –horizontal lines show distance north or south from equator Longitude – vertical lines show distance east or west from prime meridian Together, they form a grid of Earth’s surface
How latitude/longitude is divided • Latitude –horizontal lines show distance north or south from equator – Divided into degrees, minutes, seconds 1 degree = 60 minutes 1 minute = 60 seconds ex. N 45° 30’ 30” • Longitude – vertical lines show distance east or west from prime meridian – Degrees, minutes, seconds like latitude ex. W 124° 30’ 45”
Map Scales • • • Verbal – scale is stated with sentence ex. 1 inch=4 miles Graphic- image on map Fractional- can be any unit ex. 1: 24, 000 means: 1. every cm on map equals 24, 000 cms in actual distance OR 2. every inch on map equals 24, 000 inches in actual distance
Gradient of a river or slope (how steep it is) Difference in elevation (rise) divided by Distance on map (run) written as ft/mi Example: the Willamette River is 410 ft elevation at its head and 10 ft at its mouth. It flows apprx. 100 miles. What is its gradient? 410 ft -10 ft =400 ft ÷ 100 mi = 4 ft/mi
Using the Metric System The METER is the basic unit for length 1/1000 m = 1 mm 1/100 m = 1 cm 1/10 m = decimeter Meter 1 m x 10=decameter 1 m x 100 = hectometer 1 m x 1000 = kilometer To convert from cm to km, just move the decimal point 5 places to the left 453, 200 cm = 4. 5 km