Longitude
The main reference line on the Earth is called the Prime Meridian. This line runs from the North Pole through Greenwich, England to the South Pole. Longitude is measured in degrees east or west of the Prime Meridian. The maximum amount is 180 degrees. Lines of longitude are closest together at the poles and farthest apart at the Equator.

Use the map on page 4 of your Reference Tables to find the latitude and longitude coordinates for the following locations.

1. What are the coordinates of the southern tip of Greenland?
Click Here for the Answer 60 degrees north, 45 degrees west Remember that you need to use north or south with the latitude number. There are two 60 degrees, but only one 60 degrees north. Don't forget to use east or west with the longitude number.

2. What are the coordinates of the island just south of Australia?
Click Here for the Answer 42 degrees south, 145 degrees east

3. What are the coordinates of the southern tip of Florida?
Click Here for the Answer 25 degrees north, 80 degrees west Remember that all parts of the U.S. and New York State are north latitude and west longitude!!!

Using the New York State map on page 3 in the Reference Tables

Remember that each degree of latitude and longitude can be divided into 60 equal sections called minutes. The symbol for minutes is an apostrophe (').

For example the coordinates for Syracuse are 43 degrees N, 76 degrees W. These are also the coordinates for Oswego, unless we use degrees and minutes. Rounding to the nearest 5 minutes of latitude and longitude will give us the following coordinates for Oswego and Syracuse.

Don't forget that minutes of latitude and longitude increase as you move away from their reference lines on a map. Just like degrees of latitude and longitude.

Using the New York State map on page 3 in the Reference Tables answer the following questions.

1. What are the coordinates of Binghamton?
Click Here for the Answer 42 degrees 05 minutes N, 75 degrees 55 minutes W Remember that you need to use north or south with the latitude number. Don't forget to use east or west with the longitude number.

2. What are the coordinates of Mt. Marcy?
Click Here for the Answer 44 degrees 05 minutes N, 74 degrees 00 minutes W

3. What are the coordinates of Ithaca?
Click Here for the Answer 42 degrees 25 minutes N, 76 degrees 30 minutes W

Using Topographic Maps

Topographic maps or contour maps show the shape of the Earth. Contour lines connect points of equal elevations on the maps. Each contour line is separated from the next by an equal change in elevation called the contour interval.

Here are some rules that will help you understand topographic maps.

1. Contour lines never cross.

2. When a contour line crosses a river (stream) the contour line forms a "V". The "V" always points upstream. Look at the Cinder River in the diagram below and observe how the contour lines "V" toward the top of hill A. This tells you which direction the river is flowing. Remember water flows toward the lowest elevation.

3. The slope (gradient) is steepest when the contour lines are close together and gradual when they are far apart. The right side of hill A is steeper because the contour lines are much closer together.

4. Contour lines form circles or are lines that go to the edge of the map. The higher elevations on a map are found where the contour lines make smaller closed circles. See hill A on the map below.

5. A depression on a contour map is shown by contour lines with small marks pointing toward the lowest point of the depression. The first contour line with the depression marks (see hill B) and the contour line outside it have the same elevation. Based on the contour interval for this map the elevation of the first contour line with depression marks is 60 meters.

The map below shows elevations in meters and the top edge of the map points north. Use the scale below the map to measure distance on the map . This landform is an island in the ocean.



Use the map to answer the following questions.

1. What is the contour interval for this map?
Click Here for the Answer 20 meters The outer edge of the island is 0 meters (sea level) and the only labeled elevations is 100 meters. Therefore, to go from 0 to 100 in five contour lines is if each line was 20 meters.

2. What is the distance between points E and F on the map?
Click Here for the Answer 8 km The best way to get this answer is to mark point E and point F on the edge of a sheet of paper. Then compare that distance to the graphic scale found below the map.

3. What direction does the Cinder River flow?
Click Here for the Answer northwest Remember the "V"s point toward the top of the hill. Therefore the river flows in the opposite direction.

4. Calculate the gradient between points D and E.
Click Here for the Answer 15 m/km Use the gradient formula on the back of the Reference Tables. The field value is elevation. You need to find the change in elevation and the distance between the two points. The change in elevation is 60 meters and the distance is 4 km. 60 divided by 4 equals 15.

5. Which side of hill C has the steepest slope?
Click Here for the Answer south or southeast side of hill C The contour lines are closer together on this side of the hill. Therefore the slope is the steepest.

6. What is the elevation of the last depression line on hill B?
Click Here for the Answer 40 meters Go back to rule number 5. The first depression line is 60 meters. The contour interval is 20 meters and the depression marks show that elevation is still decreasing. The elevation has to be 40 meters.

To learn more about topographic maps, check out the USGS Learning Web's "What Do Maps Show: How to Read a Topographic Map" Activity Sheet.