1. Topography
shape of the earth’s surface

2. Contours Make it possible to measure the height of Mountains
Depths of ocean bottoms
Steepness of slopes

3. Contours Imaginary lines that connect points of equal elevation
Above or below a reference point
Sea level is base level or Zero feet elevation

4. contours Each contour is a line of equal elevation
Therefore, contours NEVER cross
They show the general shape of the terrain
contours

5. contours Intermediate and supplementary contours
Found in between the index contours
Help show more details of the land surface shape

6. contours Very close Indicate steep slopes Spread apart
Indicate gentle slopes

7. Contour interval Vertical space between adjacent contours
Relatively flat area – contour interval is small ex. 10 ft
Mountainous areas – contour interval is large ex. 100 ft
Interval printed on the map in the margin

8. Contour interval
The difference in elevation between one contour line and the next is ALWAYS the same on a given map
This difference is the contour interval

9. Never just stop Contour lines never end in the middle of a map
They either form a closed loop or run off the edge of the map

10. Index contours Wider Darker
Are marked along the lines with an elevation number

11. Bathymetric contours Below water level
May be blue or black dependent on location
Show the shape of the land beneath the water
Interval may vary on each map
Explained in the margins

12. Depressions Use hatchured lines to show depression
Contour interval remains the same

13. Rivers Contour lines point toward the source of a river.
In the picture in the right, the river is flowing from top right to bottom left.

14. Series Different size maps 7.5 minute series 15 minute series

15. Series The minutes refer to latitude and longitude
7.5 minute means the map covers 7.5” of latitude and 7.5” of longitude
15 minute means the map covers 15” of latitude and 15” of longitude

16. Details The 7.5” map shows more detail
The 15” map shows a larger area, therefore shows less detail