Mapping the Earth’s Surface

Chapter 3.2

Mapping the Earth’s Surface

1.Mapping the Earth’s Surfacea. Globes are very useful in

studying large features such as continents and oceans. However, they are generally too small to show small details such as streams and highways.

Mapping the Earh‘s Surface

b.To show and study the different features of earth, many different forms of maps have been developed.

c. Cartography is the science of map making and is a subfield of earth science and geography.

Map projections

1.Map Projectionsa.A map projections is a flat map

that represents the three-dimensional curved surface of a globe.

Map Projections

b. Three major map projections are Mercator, gnomonic, and conic projections.i.None of these are perfectly accurate

projections of the earth, but each one is beneficial for specific needs.

Mercator Projections1.Mercator Projections

a.This is like stretching the globe into a square or rectangle.

b.Meridians appear as straight parallel lines with an equal amount of space between them. i.This causes distortion of continents and

oceans near the poles, because on a globe meridians meet at the poles.

Mercator Projections

c. Advantages of Mercator Projectionsi.Longitude and latitude are on a grid

which makes it easy to locate positions with a simple ruler.

ii.Distortion of small areas is minimal.iii.Good tool used for navigation.

Mercator Projection

Gnomonic Projection

1.Gnomonic Projectiona.This is like placing a sheet of paper on the

globe, holding it tight so it only touches in one place, and projecting the globe’s image onto it.

b.Meridians and Parallels appear as flat lines, as if they were making contact with a globe in only one place.

Gnomonic Projection

c. Minimal distortion is caused at the point of “contact”. However, distortion increases as one moves away from the point of contact, but distortion is proportional in all directions.

Gnomonic Projectiond. Used in navigation for air travel.

i.Recall: Great circles are the shortest distance between any two points on the globe.

ii.When great circles are projected onto a gnomonic projection they appear as a straight line which can be used by pilots to find the shortest path between two points on earth.

Gnomonic Projection

Conic Projection

1.Conic Projectiona.This is like placing a paper cone over

the axis of the globe and transferring the globe’s image onto it. The cones base must touch one parallel of latitude.

b.Use in series to map a number of neighboring areas. Fitting all areas together will produce a continuous map.

Conic Projecions

c. Maps made this way are called polyconic projections.

d. Minimal distortions is present on these maps.

Conic Projections

Reading a Map1.Reading a Map

a.Maps provide information about the earth’s surface and are considered models of the earth.

b.Maps have many symbols that represent items such as cities, rivers, and roads.

c.Map symbols and meanings are explained in the map legend.

Map Legend

Map Compass

d. Maps are generally drawn with north at the top and south at the bottom. i. A compass is generally shown to state map

direction.

Map Scale

e. The scale of a map indicates the relationship between distance as shown on the map and actual distance on earth.

f. Scales may be presented as a graphic, fractional, or verbal scale.

Map Scale