Equator
The imaginary line that lies at 0 degress latitude and circles the Earth midway between the north and south poles, dividing the Earh into the northern and southern hemisphere.
Prime Meridian
The imaginary line representing 0 degrees longitude, running from the north pole, through Greenwich,England, to the south pole.
Latitude
The distance in degrees north and south of the equator.
Longitude
The distance in degrees east and west of the prime meridian.
International Date Line
An important line of longitude at 180 degrees where you will either gain or lose an entire day when you cross it. This is where all time zones meet.
Topographic Map
A map that uses contour lines, symbols, and color to show changes in the elevation of Earth's surface and features such as mountains, bridges, and rivers.
Contour Line
A line on a topographic map that connects points of equal elevation.
Contour Interval
The difference in elevation between two side-by-side contour lines on a topographic map.
Depression Contour Line
Contour lines with hachures that represent lower elevations compared to surrounding landscape.
Hachure
Short angles drawn at right angles to the contour line; found on depression lines.
Map Scale
The ratio between the distances shown on a map and the actual distances on the Earth's surface.
Gradient
The rate of change in the steepness of a slope.
Watershed
All of the land that drains into a stream, river, lake or ocean.
Run-off
Extra rainfall or snow melt that cannot be absorbed by soil and vegetation and therefore moves from the land to a body of water
Cartography
The science of mapmaking.
Remote Sensing
The process of gathering data about the Earth from far above the planet's surface.
Map Legend
A key that explains what the symbols on a map represent.
GPS
Satellite based navigation system that permits a user to pinpoint his/her exact location on Earth.
Time Zone
The differences in time of day between regions; there are 24 as a result of the Earth's constant spinning.
Electromagnetic Spectrum
The arrangement of electromagnetic radiation, including gamma rays, X-rays, microwaves, visible light, radio waves, etc...
Frequency
The number of waves that pass a given point each second.
Wavelength
The distance from the crest of one wave to the crest of another wave; the shorter the wavelength the higher the frequency, the longer the wavelength the lower the frequency.
Index Contour
A contour line that is given to you on a map so you can make other calculations using that number.