Maps

• Maps are model representations of a three dimensional world.

• Latitude and Longitude give us two dimensions

• Elevation gives us the third

• In order to fit a spherical world on a two dimensional surface maps must have some distortion.

Projections

Fields and Isolines

• A field is any region of space that has some measurable value at every point in that region.

• An isoline is a line that connects points of equal value in a field.

Type of Isolines

• Isotherm - an isoline for temperature

• Isobar - an isoline for air pressure

• Contour Line - an isoline for elevation

Rules for Drawing Isolines

• Lines must connect points of equal value

• Lines can not cross each other• Lines can not end in the middle

of the field, they must run off the edge of the field or connect with themselves

Same Latitude and Longitude

Two different elevations

Features

• Cliffs or steep slopes– Contour lines are closer together

Features

• Cliffs or steep slopes– Contour lines are closer together

Streams

As contour lines cross a stream they point upstream

Features

• Cliffs or steep slopes– Contour lines are closer together

Streams

As contour lines cross a stream they point upstream

Depressions

Pits or depressions are shown by hachure lines

Do Now

• Define the following ters:

• Gradient

• Relief

• Contour interval

• Benchmark

• Isoline

• Index Contour Line

• Haschure Line