1. Chapter 2
Topographic Maps…

2. History…… First topographic maps were made using only ground survey…
Today most maps are made by remote sensing, which is collecting data from above the ground…….
Quicker and easier,,,
More detailed and accurate…

3. Remote Sensing…..

4. Photogrammetry…..
The oldest method of aerial photography

5. Imaging Radar….
Sends out a signal, then listens for a return (echo)…

6. Landsat satellites
Use sensors to detect energy reflected from the ground….

7. Topographic Maps…..
Topographic maps are detailed maps that use contour lines to represent changes in elevation and features on Earth’s surface.

8. Contour lines….
Continuous lines drawn on a map connecting points of the same elevation…
Contour lines show:
Elevation
Shape
Steepness of the land

9. Contour interval…
The difference in elevation between 2 consecutive contour lines…..
C.I. = 20’

10. Contour Index…. Every 4th or 5th line.
Usually darker in color and marked with a number…..

11. Contour Features…. Hilltops… Plains… Form enclosed circles
Contour lines are spread out and far apart.

12. Contour Features cont….
Ridges / Cliffs
Valleys / Rivers
Long, straight lines fairly close together
Form a “v” shape and they point upstream

13. Depression…..
Depression contour lines have hachures, or short lines at right angles to the contour line. These indicate the direction of the depression .

14. Gradient (Slope)…. Lines close together = steep slope,,,
Lines farther apart = gentle slope,,,,
Slope = in elevation
Distance

15. USGS…..
The USGS issues standard topographic maps called……… Quadrangles.
2 main series…..
15 minute - covers ¼ of a degree of latitude & longitude most of these are 1:62,500 scale
7.5 minute - 1:24,000 scale, more than 2X as large, there is more detail

16. Map Legends….
A map legend explains what the symbols on a map represent.

17. Map Scale….
Map Scale – relationship between the distance on the map and real distances on Earth…