points of the compass. degrees, minutes, seconds there are 360 o degrees around a circle each degree...
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Points of the Compass
Degrees, Minutes, Seconds
There are 360o degrees around a circleEach degree can be divided into 60’
minutesEach minute can be divided into 60”
seconds
X
Global Positioning
We can use lines parallel to the equator and lines between the poles to position objects on the surface
30oN Lat 60oW Long
0 degrees Latitude (Equator)
90 degrees North Latitude
90 degrees South Latitude
Latitude
0 degrees Longitudeat Greenwich, England
X
40o0’0”N 74o0’0”W
Topo Maps Types of contours
• Every point on a contour line represents the exact same elevation
• Contour lines can never cross one another.
• Moving from one contour line to another always indicates a change in elevation.
• On a hill with a consistent slope, there are always four intermediate contours for every index contour.
• The closer contour lines are to one another, the steeper the
slope http://geology.isu.edu/geostac/Field_Exercise/topomaps/topo_interp.htm
500
Contour Interval, Scale, Series, Sectors
Use the scale to measure distanceUNITS MUST MATCH
Making a Topo Map• Suppose you measured elevations and positions with your GPS• Use the Latitudes and Longitudes you measured and lay out the elevations• Pick an elevation you will draw
Making a Topo Map• Pick an elevation you will draw
• Find a place with two nearby elevations, one larger, one smaller
Making a Topo Map• Pick an elevation you will draw
• Find a place with two nearby elevations, one larger, one smaller
• Place a X where the elevation would lie
Making a Topo Map• Pick an elevation you will draw• Find a place with two nearby elevations, one larger, one smaller • Place a X where the elevation would lie• Repeat and connect the X’s
Drawing a Cross-Section (Elevation Profile)
1. Hold a sheet of paper along line2. Mark contours3. Write elevation next to each
• Make a vertical scale (usually exaggerated)
• Make a dot at each contour at its elevation
• Connect the dots for your elevation profile
• Later we will use these to make geologic cross sections
• Topo Maps, Air Photo Pairs, GPS, etc