Measuring the Earths Dimensions Model of the Earth A model is anything that represents the properties of an object or system. 1. Physical & Mechanical 2.  Mental 3.  Mathematical 4.  Graphic Models

II. The shape of the earth A. Observations that the earth is curved. 1. Ships at Sea… 2. Eclipses… 3.  Photographs from space are the best examples proving the earth is round.  

2. Gravity meters tell us so… The earth is an oblate spheroid or a NEARLY PERFECT CIRCLE B. The circumference measured between the poles & the equator are different. 1. Slightly flat at the poles and bulging at the equator 2. Gravity meters tell us so… Gravity Stronger at the poles. Equatorial Diameter =12,756 km Polar Diameter = 12,714 km

Horizon: is where the sky touches the earth. C. Observations of Polaris lead to the conclusion that the earth is round. Parallelism: The north pole points to Polaris. The Altitude of Polaris Equals Your Latitude Altitude: is an angle measured from the horizon. Horizon: is where the sky touches the earth. Zenith: straight above your head.

Altitude of Polaris is Equal To Your Latitude = 42  North Latitude

At the equator your altitude to Polaris is 0  In New York the Average Altitude is Between 41  & 45  North

To find the North Star use the Big Dipper The 2 Pointer Stars Point to Polaris

Finding your way around…. …using Polaris

III. Locating Positions on the Earth A. Coordinate systems are used to locate points on a surface. 1. On a curved surface, such as earth, we use latitude & longitude. Both reference points are found by using stars a.    The equator is the starting point for latitude. Measured 90° North or South Latitude lines are parallel to one another & run like latter rungs.

B. The prime meridian is used for the starting point of longitude lines. Marked in 15° increments as the sun moves across the sky. Run 180 ° East or West to the International Dateline. Each meridian runs the long way meeting at the poles.

C. Latitude is reported first then Longitude 45° North by 30° West ° Degrees `Minutes ``Seconds

D. There are 24 Time Zones The International Date Line @ 180 Separates One Day from the Next. The earth rotates on its axis 15  / hour Time can be tracked by counting the number of hours away from the prime meridian.

IV. Field Maps Field Quantities A field is a region of space that has a measurable value at every location. Scalar Fields: magnitude measurements (Temperature) Vector Fields: magnitude and direction (wind speed) Iso-lines connect points of equal value. 4. Iso-surface is a three dimensional surface in which every point has an equal value.

A. Creating an Isotherm field map Connect temperature points of equal value. Identify Heat Sources and Sinks Heat Sink Heat Source

Topographic Maps gives a two dimensional view of the land. B. Topographic Maps are models showing the elevation, shape, and steepness of the land surface. Contour lines connect points of equal elevation. Topographic Maps gives a two dimensional view of the land. Show Relief or Elevation above sea level. 2000 ft. Contour line

Compass Direction & Magnetic Declination. Contour Interval 2. All topographic maps are referred to as quadrangles or contour maps. ¤ A quadrangle is a 4 cornered map. Scale showing the ratio of actual distance to map distance Compass Direction & Magnetic Declination. Contour Interval

3. Contour Interval is the change in elevation from one contour to the next. Closely Spaced Contours indicate a steep cliff gradient. A hill top has closed looped contour lines Index Contour Lines are thick lines. V-Shaped contours indicate a stream valley & point uphill

A profile….. Note the closed contours and “u” shaped valley.

4. Topographic Profiles can be drawn using contour points. A profile shows the cross sectional view of the landscape

5. Calculating a gradient or the slope of the land. ESRT pg 1 What is the gradient of the hill below the ski lift? G = Change in Field Value Distance G = 1400 ft – 450 ft 0.8 miles G = 950 ft G = 1187.5 ft/mile

Answer the following. What is the contour interval? What is the highest contour elevation? What compass direction is Campbell River from? What do closed contour lines indicate? What do closely packed contours indicate along side a hill? Which compass side of Deer Mountain is the steepest? What is the highest possible elevation for Berry Mountain? Calculate a gradient for line 1 use your ESRT ruler to estimate distances. 9. Calculate a gradient for line 2 use your ESRT ruler to estimate distances. Answer the following. Line 1 Line 2 C.I. = 100 Meters