Intro to Maps

1. Intro to Maps • Since most of you got your lab books today, I’ll give this little introduction • Normally you are expected to study the lab before coming to class

2. Points of the Compass

3. Degrees, Minutes, Seconds • There are 360o degrees around a circle • Each degree can be divided into 60’ minutes • Each minute can be divided into 60” seconds

4. X

5. 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

6. Latitude 90 degrees North Latitude 0 degrees Latitude (Equator) 90 degrees South Latitude

8. 0 degrees Longitude at Greenwich, England

10. 40o0’0”N 74o0’0”W X

11. Topo Maps Types of contours

12. 500 Use the scale to measure distance UNITS MUST MATCH Contour Interval, Scale, Series, Sectors • Every point on a contour line represents the exact same elevation • Contour lines can never cross one another. Exception: • 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

13. Contour Rules • The rule of V's: sharp-pointed vees usually are in stream valleys, with the drainage channel passing through the point of the vee, with the vee pointing upstream. This is a consequence of erosion. • The rule of O's: closed loops are normally uphill on the inside and downhill on the outside, and the innermost loop is the highest area. If a loop instead represents a depression, some maps note this by short lines radiating from the inside of the loop, called "hachures". • Spacing of contours: (repeat) close contours indicate a steep slope; distant contours a shallow slope.

15. 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

16. Making a Topo Map • Pick an elevation you will draw • Find a place with two nearby elevations, one larger, one smaller

17. 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

18. 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

19. Drawing a Cross-Section • (Elevation Profile) • Hold a sheet of paper along line • Mark contours • Write elevation next to each

20. Make a vertical scale (usually exaggerated) • Make a dot at each contour at its elevation

21. Connect the dots for your elevation profile • Later we will use these to make geologic cross sections • Topo Maps, Air Photo Pairs, GPS, etc

22. Washington and Oregon Initial Point Township and Range System • Initial Point • Meridian vertical • Baseline horizontal • Township 36 mi2 • Range distance E or W refer. principal meridian, ea. 6 miles • Section 1 mi2 Section numbers wind back and forth, edges always have same matching number