Topographic Maps and Coordinate Systems

Topographic Maps Field –A region in space in which a similar quantity can be measured at every point or location Quantity might include –Temperature –Barometric pressure –Elevation –Etc. Field map –A map on which measurements are plotted

Isolines Isolines connect points of equal value on a field map –Iso means same

Isobars –Lines that measure areas of equal barometric pressure

Topographic Maps Topographic maps show the shape of Earth’s surface Isolines on a topographic map are known as contour lines Contour lines show points of equal elevation

Topographic Maps Contour lines showing points of equal elevation

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. (*) Below the scales it says the contour interval is 20 feet. (*) Linville Falls? Contour Interval = ??? 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.) (*)

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 (*) 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. (*)

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. (*)

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 doesn’t. (*) 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 “V’s” point upstream,(*)

What was done was to draw a line that connects the tips of the “V”s. 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.

Let’s 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. (*) Linville Falls: Date = ???

Let’s 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. Let’s take a look at the scale next. (*)

Latitude and Longitude (Geographic)

Geographic Coordinates of Willow Springs, Missouri

LATITUDE AND LONGITUDE Latitude: 34° 22’ 30”; Longitude: 89° 30’ Linville Falls: Latitude ___° ___’ ___” to ___° ___’ ___” Longitude ___° ___’ ___” to ___° ___’ ___”

Scale Verbal Graphic Fractional/Ratio –1:4 –1 map unit equals 4 real units –1:1200 –1 map unit equals 1200 real units

Let’s take another look at the information at the bottom of the map. (*) This is the area of the two scales. (*) Linville Falls: Fractional Scale = ??? The top scale is called the fractional scale: Scale 1: (*) This simply means that an inch on the map is equivalent to inches on the surface of the Earth. OR 1mm on the map is equivalent to mm on the Earth’s surface. (*) One unit of ANYTHING on the map is equal to of those things on the Earth Surface. (*)

Map Scale

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. (*) What would the hill look like if you were to slice it from left to right? (*)

How to Make a Topographic Profile feet 400 feet 300 feet 200 feet 100 feet Normally, the Earth’s 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. (*)

A B 6400 The contour interval of this map is 40 feet. Every index contour would then be 200 feet 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. (*)