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