Topographic maps

Features on a Topographic Map Relief: difference in elevation between any two points– hills, valleys, mountains Water Features: lakes, ponds, streams, rivers Cultural Features: human-made features, bridges, canals, buildings, roads

Relief Relief determines contour interval i.e. difference in elevation between adjacent contour lines Contour line: imaginary line drawn on Earth’s surface connecting points of the same elevation el.com/nature_gallery/howt oreadamap.htm

Relief Bench marks: points marked by brass plates fixed permanently on the ground– provide accurate location and precise elevation Spot elevations: height of a particular point (summit, lake shorelines, road intersections)

Rules of Contour Lines Where a contour line crosses a stream or valley the contour bends to form a “V” that points upstream or valley

Rules of Contour Lines Contours near the upper parts of hills form closed polygons– the top of the hill is higher than the highest closed contour Depressions without outlets are shown by closed, hatched contours

Rules of Contour Lines Contours are widely spaced on gentle slopes Contours are closely spaced on steep slopes Evenly spaced contours indicate a uniform slope Contours do not cross or intersect one another (unless there is a rare, overhanging cliff) All contours eventually close, either on a particular map or beyond its margins

Rules of Contour Lines A single higher elevation contour never occurs between two lower contours or vice versa A change in slope is always determined by the repetition of the same elevation either as two different contours of the same value or the same contour crossed twice

Scale Scale: expression of the relationship between the distance on the map and the true distance on the Earth’s surface Generally expressed as ratio or fraction: 1:24,000 means that a distance of on 1 unit on the map = 24,000 such units on the ground (meter, feet)

Scales Typically Used

Colors and Symbols Blue = water featuresGreen = woodlands, orchards, etc. Red = urban areas, important roads, public land boundaries, civil boundaries Black = human-made worksBrown = contour linesPurple = new additions, revised versions, usually human-made features

Symbols

How Accurate can Latitude and Longitude get? At the equator, one degree of latitude or longitude represents approximately 70 statute miles Latitude stays the same because they are always equally spaces apart.

Longitude If you look on a globe you will see that the lines of longitude get closer together as they approach the north and south poles. At higher latitudes the distance of one degree of longitude decreases.

Degrees, Minutes and Seconds 1 degree is divided into 60'(minutes) 1 minute is divided into 60"(seconds) 1 degree = 70 miles 1' = 1.2 miles 1" =.02 miles

Prime Meridian From Pole to Pole, the Prime Meridian covers a distance of 20,000 km. In the Northern Hemisphere it passes through UK, France and Spain in Europe and Algeria, Mali, Burkina Faso, Togo and Ghana in Africa. The land mass crossed by the Meridian in the Southern Hemisphere is Antarctica. The prime meridian is 0 degrees longitude.

Equator The equator is 0 degree latitude. This imaginary line, which runs through parts of South America, Africa, and Asia, is officially the halfway point between the North Pole and the South Pole.