Intro to Maps

Since most of you purchased 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 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