Welcome! Check your mailboxes Please get your Density packets and Density labs

Why make maps? To represent a larger area than we can see To show a phenomenon or process we can’t see with our eyes To present information concisely To show spatial relationships

Represent a larger area

Present info concisely

Differences in kind

Topographic Maps

How do we read maps? Size of the map relative to reality (scale) What’s on the map (symbolization) Shape of the map (projection)

Symbols indicate and describe locations

Map scale Ratio of the distance on the map to the distance on the ground Tells you how a maps features compare in size with the Earth’s surface Can be graphical or verbal (1 in = 10 miles)

Large-scale Small-scale

Map Projections Because Earth is spherical, it can be difficult to map features to a 2D surface without distortion

Map projections are used to map our Earth in a way that’s flat. There is always some degree of distortion.

Mercator Map A map that shows the entire Earth but is distorted at the poles is known as a Mercator map.

Polyconic projection Projection of the Earth onto multiple cones, Very accurate for small areas. Polyconic projections are used for topographic maps.

Latitude and Longitude Finding Your Location on a Sphere

PSC 121 Prince George’s Community College Barbara Gage Coordinate Systems On a body such as the Earth or our moon, we can pinpoint the location of any city or landmark using two values, the latitude and longitude. On a body such as the Earth or our moon, we can pinpoint the location of any city or landmark using two values, the latitude and longitude.

PSC 121 Prince George’s Community College Barbara Gage Latitude Latitude is defined as the location of a point above (or below) the equator. Latitude is defined as the location of a point above (or below) the equator. The measurement is expressed in degrees, minutes, and seconds. The measurement is expressed in degrees, minutes, and seconds. The equator is at 0° and the poles are at 90°. The equator is at 0° and the poles are at 90°.

PSC 121 Prince George’s Community College Barbara Gage Latitude If the location point is north of the equator an N or + is added to the degrees. If the location point is north of the equator an N or + is added to the degrees. If the point is to the south of the equator an S or – is added to the value. If the point is to the south of the equator an S or – is added to the value. 52°N or +52° 24°S or -24°

PSC 121 Prince George’s Community College Barbara Gage Latitude Lines of latitude are also called parallels. Lines of latitude are also called parallels.

PSC 121 Prince George’s Community College Barbara Gage The Equator is a line of latitude that divides the Earth into the Northern Hemisphere and the Southern Hemisphere. The Equator is a line of latitude that divides the Earth into the Northern Hemisphere and the Southern Hemisphere.

PSC 121 Prince George’s Community College Barbara Gage Longitude Longitude is defined as the measurement of the location point east or west of the Prime Meridian Longitude is defined as the measurement of the location point east or west of the Prime Meridian The value is also expressed in degrees, minutes, and seconds. The value is also expressed in degrees, minutes, and seconds. Note: There are 60 minutes in a degree and 60 seconds in a minute.

PSC 121 Prince George’s Community College Barbara Gage Longitude If the point is located to the west of the Prime Meridian we add a W to the value. If the point is located to the west of the Prime Meridian we add a W to the value. If the point is located east of the Prime Meridian we add an E after the value If the point is located east of the Prime Meridian we add an E after the value 30°W 80°E

PSC 121 Prince George’s Community College Barbara Gage Longitude Longitude lines are also known as meridians. Longitude lines are also known as meridians. The Prime Meridian has a value of 0° and no E or W. The longitude values increase up to 180° in both directions. The Prime Meridian has a value of 0° and no E or W. The longitude values increase up to 180° in both directions.

PSC 121 Prince George’s Community College Barbara Gage The Prime Meridian is a line of longitude that divides the Earth into the Western Hemisphere and the Eastern Hemisphere. The Prime Meridian is a line of longitude that divides the Earth into the Western Hemisphere and the Eastern Hemisphere. It runs through Greenwich, England. It runs through Greenwich, England.

PSC 121 Prince George’s Community College Barbara Gage Longitude and Time The Earth is split into 24 meridians, you will dividing the Earth into 24 zones, corresponding to the 24 hours in a day. These are our time zones. The Earth is split into 24 meridians, you will dividing the Earth into 24 zones, corresponding to the 24 hours in a day. These are our time zones.

PSC 121 Prince George’s Community College Barbara Gage Longitude and Time As you travel around the world to the east, you gain an hour in time for each zone you cross. If you travel to the west you lose an hour. As you travel around the world to the east, you gain an hour in time for each zone you cross. If you travel to the west you lose an hour.

PSC 121 Prince George’s Community College Barbara Gage The 180° meridian signals the change of date point. This is called the International Date Line. The 180° meridian signals the change of date point. This is called the International Date Line. Travel east and the date goes back one day; travel west and you advance a day when crossing this meridian. Travel east and the date goes back one day; travel west and you advance a day when crossing this meridian.

PSC 121 Prince George’s Community College Barbara Gage But… To keep all of a country in the same time zone, the International Date Line does not follow the 180° meridian exactly. To keep all of a country in the same time zone, the International Date Line does not follow the 180° meridian exactly. Other time zones make the same accommodations for country or state boundaries. Other time zones make the same accommodations for country or state boundaries.

PSC 121 Prince George’s Community College Barbara Gage

Latitude = flatitude!

PSC 121 Prince George’s Community College Barbara Gage Longitude = long cat!