Notes on Topographic Maps

A.    Fields:

a.      A field in a region of space in which a similar quantizes can be measures at every point or location.  Isolines connect points of equal value on a field map.

 

EX1: Isotherms like all isolines represents points of equal value in region.

                                 

 

 

 

 

 

 

B.     Types of Isolines

1.       Isotherms:  Connect points of equal temperature

2.     Isobars:  Connect Points of equal air Pressure

3.     Contour lines: Connect points of equal elevation.

 

 

Topographic Maps

Topographic or Contour Maps shows the shape of the Earth’s surface in two dimensions.

The measures elevations of an area are represented by Contour Lines, which are drawn on a map and represent equal points of elevation.

The darkest lines are known as Index Contours.  These lines are usually labeled indicating a particular elevation.

The Contour Interval is determining the difference in feet or meters between two index contours and dividing by the number of contour line between the two index contours.

The directions of Stream Flow can be determined by:

1.       Remember:  Streams always flow from high elevation to low elevations

2.     The Law of “V”’s.  When looking at the map, look at where contour lines cross a river.  The contour lines will bend. The bend of the contour line will indicated the source of the river.

3.     The slope, or gradient, is the steepest where the contour lines are the closest together.

4.     The highest elevations of a map are found where the contour lines make the smallest curves.

5.     A closed depressions is illustrated by a contour line with small marks projecting toward the lowest part inside the depression

 

C.     Topographic Profiles:

Topographic Profile is a cross sectional view that shows the elevation of the land along a particular baseline. 

                                 

Given the topographic map above, lets draw a profile map from point P to point Q. First, we need a horizontal grid that represents the distance from P-Q

 

Next, transfer the points from the contour map to the grid

 

 

Then connect the points with a smooth line to draw the profile

 

We have a cross section of the landscape.