Topographic (Topo) Maps (also called Contour Maps) Show surface features or topography Shows elevation or height above mean sea level; show relief (elevation differences). Show natural features such as rivers and hills, and man-made features such as buildings and roads. Made by using aerial photography and survey points collected in the field. An aerial view of an island shows the shape of the island but does not indicate the islands size or elevation. A typical map projection would show the islands size and shape but would not show the islands topography. A topographic map provides more detail about the surface of the island than either the drawing or the porjection map does. The advantage is that a topo map shows the islands size, shape an elevation. Show size, shape, and elevation.

Isogram a line on a map that represents a constant or equal amount of a given quantity. All points along an isogram share the same value (iso means equal) Isograms never cross Isotherms – lines connecting points of equal temperature. Isobars of equal air pressure

Contour lines are isograms that show points of equal elevation Contour line – a line that connects points of equal elevation. They never cross, and are measured from mean sea level. Contour interval – the difference in elevation between one contour line and the next. Relief – the difference in elevation between the highest and lowest points of the area being mapped. Index contour – refers to every fifth contour line marked bolder than the four lines on either side and labeled with the elevation. X – benchmarks show exact elevations that are labeled. each contour line is an isogram that connects points that have the same elevation. Areas of high relief have greater contour intervals than areas of low relief.

Contour Intervals…Index Contours A Contour Interval is the difference between one line and the next line (designated on map). An Index Contour is every fifth line that is bolded and has the elevation marked on it.

Drawing Contour lines… contour interval = 50 m

Topo maps show elevation

Closely spaced lines – steep slopes widely spaced lines – gradual slope Close – elevation change is rapid

V’s in contour lines show valleys - V’s point uphill or upstream. - The stream or river flows in the opposite direction. - The width of the V shows the width of the valley

Depression Contours (show decreasing elevation) In the valley, many of these depressions are sinkholes due to our Karst topography (caves in limestone).