# Introduction to Maps - PowerPoint PPT Presentation

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## Introduction to Maps

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### Map Projections. Method of turning the globe into a flat surface ... Many maps can't have one scale due to distortion. Large scale: the map closer to the ... – PowerPoint PPT presentation

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Title: Introduction to Maps

1
Introduction to Maps
2
Models
• Used to show unfamiliar things in a familiar way
• Might not always look the same as the actual
thing
• Must behave the same as the actual thing

3
Reasons to use Models
• 1. real thing is too big or too small
• 2. real thing is too dangerous
• 3. real thing is to expensive
• 4. real thing is too far away
• 5. help understnd how the real thing works (let
you see the insides)

4
Map Projections
• Method of turning the globe into a flat surface
• No map can ever show all 4 of the following
• 1. true direction
• 2. true distance
• 3. true area
• 4. true shape

5
Types of Map Projections
• Mercator
• true direction
• true distance along the equator
• areas and shapes distorted, especially near poles
• Robinson
• true direction along all parallels and central
meridians
• distances constnat along parallels, but scales
vary
• area and shapes less distorted than Mercator

6
Mercator vs. Robinson
• Mercator projection
• Robinson projection

7
Types of Map Projections Cont.
• Gnomonic
• a straight line between 2 points shows the
shortest route between the 2 points.
• used for planning long land, sea, or air voyages
• Polyconic
• the most accurate conical represntation
• cone placed in contact with map

8
Gnomonic vs. Polyconic
• Gnomonic Projection
• Polyconic Projection

9
Coordinate Systems
• Latitude
• latitiude parallels that circle the world
running east to west
• equator is 0 degrees latitude
• poles are 90 degrees north and south
• one degree is divided into 60 minutes
• latitude is a measure of distance

10
Coordinate systems cont.
• Longitude
• longitude meridians that run pole to pole going
north and south
• prime meridian is 0 degrees
• international date line is 180 degrees
• longitude is a measure of time 15 degrees 1
hour time difference

11
Public Land Survey
• developed to divide land for selling
• each state has principal meridians and baselines
• townships (36 sq. miles each) are numbered in
reference to meridians and baselines
• 36 sections (1 sq. mile each) make up each
township, and can be further divided

12
Map scale
• Ratio of distance on the map to distance on earth
• Many maps cant have one scale due to distortion
• Large scale the map closer to the acutal land
size
• Small scale the map is more in-depth on roads,
building, etc.

13
Map Type / Features
• Maps can show many different types of
information
• land use
• landforms
• elevation
• natural resources
• political boundaries
• topographic or contour maps

14
Topographic or Contour Maps
• Rules of Contour Lines
• a contour line connects points of equal elevation
• contour lines do not cross
• closely spaced contour lines represent steep
slopes
• widely spaced contour lines represent gentle
slopes
• contour lines V up stream valleys (they form a
V that points upstream)
• relief the highs and lows on the earths surface

15
Rules cont.
• a closed contour line (loop) represents a hill
• a closed contour line with hachure marks
represents a depression
• the contour interval is the set or established
elevation change that happens between two
successive contour lines