MAPPING EARTHHow are Earth’s surface features measured and modeled?

HOW DO WE LOCATE POSITIONS ON EARTH?

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We use a coordinate system much like the game of Battleship.

What do we use to determine these coordinates?

Answer: Latitude and Longitude

Coordinate System: a grid of imaginary lines that are used to locate a point on a two-dimensional surface (a map)

HOW DO WE LOCATE POSITIONS ON EARTH?

HOW DO WE LOCATE POSITIONS ON EARTH?

Latitude-Longitude System: the most commonly used coordinate system for the Earth. This system is based on observations of the sun and other stars.

LINES OF LATITUDE

Lines of Latitude (Parallels): Measures distance north or south of the

equator (0°) 90° at Poles Parallel

LINES OF LONGITUDE (MERIDIANS)

Measures distances east or west of the Prime Meridian (Prime Meridian is 0--180 is highest)

Lines connect at the north and south poles

SAINT LOUIS - 38.6272° N, 90.1978° W

HOW DO YOU DETERMINE LATITUDE? The angle that Polaris makes with the horizon is equal to

the person’s latitude (Polaris never moves)

Altitude = Latitude

HOW DO YOU ESTIMATE LONGITUDE? Find the time difference between your local time and

Greenwich Mean Time (GMT) and then multiply by 15 (Greenwich is at 0 Longitude) This works because the Earth rotates 15 every hour and

the Time Zones are 15 longitude apart (24 total, 1 hour apart)

If your time is EARLIER than the time given for GMT, then you are WEST of the Prime Meridian

If your time is LATER than the time given for GMT, then you are EAST of the Prime Meridian

U.S. TIME ZONES

Topographic Map: shows the shape of Earth’s surface by using contour lines (the shape of the lines indicate the shape of the land)

Topographic Mapping

WHAT ARE CONTOUR LINES?

lines of equal elevation (height above sea level)

WHAT TO LOOK FOR WHEN LOOKING AT TOPOGRAPHIC MAPS:

Contour Interval: difference in height between two adjacent contour lines

WHAT TO LOOK FOR WHEN LOOKING AT TOPOGRAPHIC MAPS:

Scale: distances on a map represent the actual distance on the ground

WHAT TO LOOK FOR WHEN LOOKING AT TOPOGRAPHIC MAPS:

Map Direction: often indicated by some type of arrow pointing north (if there is no arrow, then north is the top of the map)