Unit 2- Dimensions of

the Earth

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Shape of the Earth

Oblate Spheroid- We are a little tubbier around the middle by about 88 miles. Scaled down to the size of the image in your handout- the Earth will look perfectly round!


What would the earth be like it it was flat

Proof of Earth's shape


1. Ships disappeared over the horizon.

2. When observers travelled northward Polaris moved higher in the sky.

3. Photos from space!


Latitude and Longitude

Latitude and Longitude are imaginary lines that we use for orientation and locations on globes or maps.


Longitude runs from North to South, and Latitude runs from East to West.


To find Longitude measurements look at the numbers on the top and bottom of the topographic map.

To find Latitude, see the numbers on the sides of the map.


The latitude is written before the longitude. Ex. 41 degrees N, 73 degrees W, written 41 N, 73 W.

Remember: There are 60" (seconds) in a minute and 60 ' (minutes) in a degree.


ex. 30.5 degrees N= 30 degrees 30' N (1/2 of 60) not 30 degrees 50' N (1/2 of 100).

Video on Latitude and Longitude and the Reference Tables

NY State Latitude and Longitude


Topographic Maps

A topo (topographic) map is a map that shows elevation. It is always good to have back up when going wilderness hiking.


Contour lines show elevation above sea level.

Contour interval is the amount of elevation change between each contour line.


Augmented Reality Sandbox

Isolines- connect points of equal value


Practice video part 1

Practice video part 2

Intro to Topographic Maps



Rules of Contours

The closer together the contour lines the steeper the slope.

Contour Lines don't cross, end or branch with another contour line.

Hill top contours look like a bull's eye with concentric circles around the hill.


Contours with depression marks means the contours are decreasing in bowl formation such as in a mountain lake or volcanic crater.

When a contour lines crosses a river/stream it makes a "V". The point of the "V" points uphill. A river flows opposite the point of the "V".


Stream flow YouTube





Gradient= Change in elevation/ Change in distance.

1. To calculate the change in elevation- Find the elevation of the beginning and end points and subtract the difference between the two.

2. To find the change in distance- On a scrap piece of paper, mark the distance between the two points. Place your marked distance against the distance scale on the bottom of the map.


Note: Scales don't always start at zero and may have several different values listed so watch out.

Gradient of a Slope YouTube



Cross Section

To find the cross section of a topographic map, you must sketch the elevation of the points along the cross section line at different intervals.


1. Place a scap sheet of paper against the cross section line on the topo map.

2. Mark every time the contour lines cross the cross section line and label each elevation on the scrap paper.

3. Place the scrap paper on the bottom of your graph. (Label the elevation heights on the Y-axis if neccessary.)

4. Make a mark on the bottom of the graph every time you see a mark on your scrap paper. Now, make a series of dots on your graph paper going straight upwards from each mark until you reach the labelled elevation for that mark. Mark that location with a large dot.

5. When you are done, connect the dots to form a line graph.


Note: Be sure to curve your lines above and below any two repeating points.

How to Draw a Topographic Profile

Profile Diagram