Transcript Mapping the Earth’s Surface

Mapping the Earth’s Surface
Chapter 3.2
Mapping the Earth’s Surface
1.Mapping the Earth’s Surface
a. 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 Projections
a.A map projections is a flat map
that represents the threedimensional 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 Projections
1.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
Projections
i.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 Projection
a.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 Projection
d. 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 Projection
a.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 Map
1.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