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
