READING ELEVATIONS

 
Lets go back to the Spruce Knob area and practice reading elevations.  On the map below are 10 squares labeled A through J.  Estimate the elevation for the point marked by each square (make sure to use the point under the square, not under the letter).  Compare your answers to the answers below. Recall that we determined the contour interval on the previous page.
 

Elevation is in feet

 

 

ELEVATION of Points:

A.   4400 ft  Point A sits right on a labeled index contour.  Just follow along the contour line until you reach the label

B.   4720 ft   Point B sits on a contour line, but it is not an index contour and its elevation is not labeled.  first lets look for a nearby index contour.  There is one to the south and east of point B.  This contour is labeled as 4600 ft.  Next we need to determine if point B is above or below this index contour.  Notice that is we keep going to the southeast we find contour lines of lower elevations (i.e. 3800 ft.).  This means as we move away from 4600 ft. contour line toward point B we are going up hill.  so point B is above 4600 ft.  Count the contour lines from 4600 ft to point B, there are three.  Each contour line is 40 ft. (from our previous discussion of the contour interval) so point B is 120 ft. above 4600 ft, that is it is 4720 ft.

C.  4236 ft    Point C sits right on a labeled bench mark so its elevation is already written on the map.

D.  4360 ft.  Point D is on an unlabeled contour line.  From our discussion of point B above, you can see that point D is on the slope below Spruce Knob.  Just above point D is an index contour.  If we trace along this contour line we see its elevation is 4400 ft.  Since point D is the next contour line down hill it is 40 ft lower.

E  3800 ft.     Point E is on an index contour.  Follow along this contour line until you come to the 3800 label.

F.  ~4780 ft.  Point E does not sit on a contour line so we can only estimate its elevation.  The point is circled by several contour lines indicating it is a hill top (see the later discussion of depression contours to see why we know this is a hill).  First lets figure out the elevation of the contour line that circles point F.  Starting from the nearest index contour line (4600 ft) we count up by 40 for the four contour lines.  This gives us 4760 ft (4600ft + 40 ft. x 4).  Because point F is inside this contour line it must have an elevation above 4760 ft., but its elevation must be less than 4800 ft, otherwise there would be a 4800 contour line, which is not there.  We don't really know the elevation, just that it is between 4760ft. and 4800ft.

G.  4080 ft.   In order to determine the elevation of point G we first must recognize it is on the western slope of Spruce Knob.  Looking at the index contours we see that point G is between 4400 ft and 4600 ft contours.  (It is a good idea to check the elevations by counting by 40 for each of the contour lines between 4400 and 4600.  If the numbers do not work out it may mean that the contour lines, and therefore the topography, are more complicated than a simple slope.  That is not the case here.) Counting up two contour lines from 4400 ft. gives our elevation of 4080 ft.

H.  ~4100 ft.   Point H is circled by a contour line indicating it is the top of a small hill.  Its elevation is determined the same way we determine the elevation of Point F.  Find the index contour below point F (4000 ft) and count up for the two contour lines (4080 ft).  Point F is above this elevation but below 4120 ft because this contour line is not present. 

I  ~3980 ft.  Point I is also not on a contour line.  It is also not on the top of a hill because a contour line does not encircle it. Instead it is in between to contour lines on the side of a hill.  One of the contour lines is the 4000 ft index contour.  The other contour is 3960 ft contour (40 ft lower, you can tell it is lower because you are moving toward the stream which is in the bottom of the valley).  The elevation of point I is between 3960ft and 4000ft.  since point I is midway between these two contours we can estimate its elevation as midway between 3960 and 4000.

J ~ 3820 ft.  The elevation of point J is found the same way as the elevation of point I.

 

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Last Updated: 01/18/2014

 

 
 
 

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