1.2MAPPING TECHNIQUES

The Global Grid

The science and study of map making is known as cartography.Scientists use two special

measurements to describe location:

○ Latitude: the distance north or south of the equator, measured in degrees.

○ Longitude: the distance east or west of the prime meridian, measured in degrees.

The Global Grid Lines of latitude run E-W

and measure N-S.The line of latitude around

the middle of the globe, at 0 degrees (°), is the equator.

Lines of longitude run N-S and measure E-W.The prime meridian marks 0°

of longitude.

Map Projections A flat representation of Earth’s

surface is called a map.However, we know the Earth is round

… Christopher Columbus?

Maps can also be called projections since they attempt to show a three-dimensional image in two dimensions.

No map is perfect because something will always be distorted (too small, too big, out of place, etc).

Map Projections Cylindrical Projection: A map where the Earth’s

surface is projected onto a cylinder wrapped around a globe.The equator is the viewpoint (center of the cylinder).

Common example:Robinson

Map Projections Azimuthal Projection: A map where the Earth’s surface

is projected onto a flat plane at a central point.The poles are the viewpoint (center of the plane).

Common example:

Gnomonic

Map Projections Conic Projection: A map where the Earth’s

surface is projected onto a cone surrounding a globe.The poles are the viewpoint (center of the cone).

Common example:Simple Conic

Topographic Maps A topographic map is a

representation of Earth’s three-dimensional surface in two dimensions showing elevation.

Uses contour lines, or lines showing points of equal elevation.Every position along a single

contour line is the same elevation.

Topographic Maps Adjacent contour lines

represent a change in elevation.

The contour interval is the difference in elevation between adjacent contour lines.

Every 5th line is called an index contour, which is a bold and labeled with elevation.

Topographic Maps

Contour lines close together represent a steeper slope while lines further apart indicate a gentler slope.

Topographic Maps

Contour lines forming a circle represent a hill or mountain.

Topographic Maps

A depression is represented by circular contour lines having hachure marks, pointing to the center of the circle.

Topographic Maps

Contour lines do not cross each other, divide, or split.

Contour lines trend UP valleys and form a “V” or a “U” when they cross a stream.

Topographic Maps A map is drawn to scale where a certain

distance on the map is equal to a certain distance at the surface.

The scale to the right reads 1:24,000. This means 1 unit on the map is equal to 24,000 units on the ground.

If the 1 stands for 1 cm. on the map, it stands for 24,000 cm. on the ground.

How many kilometers does the 24,000 stand for on the ground?

Topographic Maps

DIMENSIONAL ANALYSIS AGAIN!

? km. = 24,000 cm. x 1 km.100,000 cm.

Try another: The same scale reads 1:24,000. However, this time, I know the 1 stands for 1 inch. How many feet does the 24,000 stand for on actual ground?

? ft. = 24,000 in. x 1 ft. 12 in.

0.24 km.

2000 ft.

Map ScaleLarge Scale – show a small area (ZOOM IN).

Example 1:24,000

Map ScaleSmall Scale – show a large area (ZOOM OUT).

Example 1:1,000,000