LAB TOPIC: TOPOGRAPHIC MAPS (C) 24 points
Introduction:
There are a variety of different types of maps; road maps, political maps,
land use maps, etc. Many maps deal only with the two-dimensional location of
places or objects without taking into account terrain, especially elevation.
Topographic maps make use of a system of contour lines to show elevation and
shape of the land. They will also indicate how steep a landscape is since as a
terrain changes elevation the lines may be closer or further apart. This would
help to determine how steep an area is. Topographic maps sometimes also show
natural features such as lakes, and can include manmade features as well.
The concept of topographic maps is fairly simple. Contour lines are drawn
on the map to represent lines of equal elevation. To help you visualize this,
picture a mountain and imagine slicing through it with a sheet of glass. The
intersection of the glass with the land surface would be a contour line. If you do
this every 100 feet you would then be able to use this information to draw a map
of the mountain going from the zero or lowest level to the highest and the series
of lines would be the contour lines. The contour interval in this case would be 100
feet. However you can’t assume that a point in between these lines has any
specific height unless it is indicated on the map. The legend for each map is
given at the bottom. If a map shows a feature or marks a spot with an X this
usually means that it is higher than the last contour line but is not high enough for
the next contour line. It is somewhere between. Depressions are areas that are
lower than the contour line they are within. These are marked with hatch lines.
A point indicated within two lines, for instance between a 50 foot mark and
a 100 foot mark with no other information is assumed to be at the lower indicated
elevation. In this case the point would be considered to be at 50 feet.
Maps will give you a legend at one margin and also a compass rose. The
following exercise is to introduce you to and give you some practice with the
concept of topographic maps.