Mapping Exercise 1: (Topographical maps)

You are looking at an area of a USGS topographical map.  A topographical map takes a 3-demensional measurement (elevation) and draws it on a flat surface. The map contains contour lines that represent lines of the same elevation (the distance of something above sea level) on the ground. The contours lines are brown.  The thicker brown lines are labeled with a number; this number represents the elevation.  It could be English units or Metric so make sure that you check the legend of map. 

You can find the elevation of a contour line by first finding a thicker contour line.  Trace the thicker line until you see an elevation number.  If you need the elevation of a contour line that does not have a number, you are going to have to figure out the contour interval (The contour interval of a topographic map is the change in elevation between contour lines). To get the contour interval, take two known elevations and find their difference (e.g. 2900 – 2700 = 200).  Then count the number of intervals (contour lines) between the two thicker contours (e.g. 10).  Divide the distance between elevations by the number of contour lines and subtract that figure from the known elevation.  If the difference is 200 and there are 10 intervals, that gives us 20 units per interval. If we know our contour interval to be 20 and we are looking for an elevation on the line that is two lines below the 2900 ft contour line, your elevation is 2860 ft (2900 – 40 = 2860).  If you have 4 lines between two thicker contour lines labeled as 700 and 800, the interval is 20.

Other features on topographic maps are streams and they are shown in solid blue lines. Intermittent streams (streams that do not flow year round) are drawn with long blue dashes and dots.  The following are also included on USGS maps and located in the legend.

• Forest: Shown in green
• Unforested areas: White; May be grass, sand, or some other surface
• Roads: Two parallel lines; Unbroken lines indicate paved roads, broken lines unpaved
• Trails: Dashed lines
• Marshy Area: Blue symbols enclosed by blue dashed line
• Buildings: Building shapes shown, may be filled or unfilled

Please complete the following:

1. Find and highlight Smith Brook.
2. What is the distance between contour intervals on the map?  (*Note: elevation is in feet.)
3. What is the highest elevation on this map? 
4. What is the lowest?
5. What is the elevation of Lake George?
6. Circle the mouth or outlet of Smith Brook (where it runs into Lake George).
7. Put a square around the two headwaters (where the brook begins).
8. The white area that runs along Route 9N (thick red line with black outlines) in the map is designated as ______________  probably due to _____________.