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

Points of the Compass

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

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

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

0 degrees Longitude at Greenwich, England

40o0’0”N 74o0’0”W X

Topo Maps Types of contours

Every point on a contour line represents the exact same elevation 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

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.

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) Hold a sheet of paper along line Mark contours 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

Township and Range System Washington and Oregon Initial Point 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