Slide 1

Topographic Maps Topographic maps show the shape of Earths surface and other surface features, such as roads, buildings, streams, cemetaries, mines, etc. Isolines on a topographic map are known as contour lines Contour lines show points of equal elevation Slide 2 Topographic Maps Contour lines showing points of equal elevation. Every fifth line (Index Line) is bold and may be numbered. Slide 3 Here is an image of the bottom of the map. There is a lot of information located here, but for now take a look at the area below the graphical scales. (*) Three graphical or bar scales are also shown. Below the scales it says the contour interval is 20 feet. (*) Below this it also states: Dotted lines represent 10-foot contours. (Below that it states that the data for the contour lines was bases on information obtained in 1929.) (*) Slide 4 Contour Lines: What is the elevation of the little unnamed hill just above it? Remember the purple line is the 1700 foot line. (*) Summit Going up to the summit (blue dot) of the hill, the next INDEX CONTOUR line is the 1800 foot line (red line). (*) BUT, we are not yet quite to the summit. There are 3 normal contour lines. The next contour line would be the 1920, the next is the 1940 and the one closest to the summit is the 1960. (*) Finally, there is one more index contour line closer to the summit. This is the. foot contour line (black) (*) 1900 So, the summit of this hill is a little over 1960 feet. But it is below 1980 otherwise there would be another contour line. (*) Slide 5 Contour Lines: While your looking at Squaw Peak, notice that the brown contour lines have different spacing. Where the contour lines are close together, there is a steeper slope. Where the contour lines are farther apart, the slope is more gentle. (*) Slide 6 Contour Lines: One last thing about contour lines is that they V upstream when they cross a river drainage. Blue represents water features on topographic maps, and the line and three dot pattern of the streams on this map indicate an intermittent stream sometimes it flows and sometimes it doesnt. (*) Next, notice how the contour lines form a V and that the V points towards the top of Squaw Peak (higher elevation), The rule of thumb is that the Vs point upstream,(*) Slide 7 What was done was to draw a line that connects the tips of the Vs. In this illustration of North Mountain Park all the stream drainages will be highlighted in purple. It includes the blue stream lines as well as the unmarked drainage. Slide 8 Lets take another look at the information at the bottom of the map. (*) This is the name of the map and when it was created. Photorevised means that the map was reevaluated in 1982 and that changes to the 1965 map were indicated in purple. Obviously, the map needs to be revised again. (*) Slide 9 Lets take another look at the information at the bottom of the map. (*) This is the location of the Sunnyslope Quadrangle with respect to the rest of the state of Arizona. Lets take a look at the scale next. (*) Slide 10 Lets take another look at the information at the bottom of the map. (*) This is the area of the two scales. (*) The top scale is called the fractional scale: Scale 1: 24000. (*) This simply means that an inch on the map is equivalent to 24000 inches on the surface of the Earth. OR 1mm on the map is equivalent to 24000 mm on the Earths surface. (*) One unit of ANYTHING on the map is equal to 24000 of those things on the Earth Surface. (*) Slide 11 Latitude and Longitude (Geographic) Slide 12 Geographic Coordinates of Willow Springs, Missouri Slide 13 Slide 14 Scale Verbal Graphic (Bar Scale) Fractional/Ratio 1:24,000 1 map unit equals 24,000 real units 1 in on map = 24,000 inches on the ground or 2,000 feet 1 cm on map = 24,000 cm on the ground Slide 15 Map Scale Slide 16 How to Make a Topographic Profile This represents a very simple topographic map of a hill. The hill is steep on the left side (the contour lines are very close together) and has a gentle slope on the right side. The numbers represent the elevation of the contour lines. (*) 100 200 300 400 What would the hill look like if you were to slice it from left to right? (*) Slide 17 How to Make a Topographic Profile 100 200 300 400 400 feet 300 feet 200 feet 100 feet 0 feet Normally, the Earths surface is not this blocky. In a topographic profile a line is drawn from these points (red dots) producing a smooth transition. (*) Thus you have a topographic profile. This is what the hill would look like if you were to cut it along the profile line and look at it from the side. (*) Slide 18 A B 6400 The contour interval of this map is 40 feet. Every index contour would then be 200 feet. 8000 7000 7600 7400 7200 7800 6800 6600 In this region the profile line cut across the 7800 foot line 4 times. (*) The last step is to simply connect the dots. (*) The profile is finished. (*)