Chapter 2 Portraying Earth Maps, Globes, Projections

Two main concepts in this chapter: The basic characteristics of maps, their capabilities and limitations as tools for geographic study The basic characteristics of maps, their capabilities and limitations as tools for geographic study The various ways a landscape can be portrayed The various ways a landscape can be portrayed 1. Map projections 2. Globes 3. Photographs 4. Remotely sensed images

Nature of Maps Maps are 2 dimensional representations of selected data Maps are 2 dimensional representations of selected data Basic attributes are to show: Basic attributes are to show: distancedistance directiondirection sizesize shapeshape Maps show thematic data: Maps show thematic data: patternspatterns distributionsdistributions weatherweather soil typessoil types Remember: a map is an attempt to show a curved surface on a flat piece of paper

Scale Scale is the ratio between length measured on a map and the corresponding distance on the ground. Scale is the ratio between length measured on a map and the corresponding distance on the ground. Scale allows you to measure distance, area, and compare sizes. Scale allows you to measure distance, area, and compare sizes. There are 3 types of scales: There are 3 types of scales: 1. Verbal 2. Numeric or Fractional 3. Graphic

Verbal Scale States in words the ratio of the map scale length to the distance on Earth’s surface States in words the ratio of the map scale length to the distance on Earth’s surface i.e. “five centimeters to ten kilometers” i.e. “five centimeters to ten kilometers” Or “one inch to one mile” Or “one inch to one mile”

Graphic Scale A graduated line that measures distances on a map, chart, or photograph in terms of ground distance A graduated line that measures distances on a map, chart, or photograph in terms of ground distance The advantage of a graphic scale is that you can measure distance directly on a map The advantage of a graphic scale is that you can measure distance directly on a map

Fractional Scale Compares map distance with ground distance by proportional numbers Compares map distance with ground distance by proportional numbers Expressed as a fraction or ratio Expressed as a fraction or ratio i.e. 1/10,000 or 1:10,000 i.e. 1/10,000 or 1:10,000

Large and Small Scale Maps A large scale map has a small denominator 1:500 or 1/500 A large scale map has a small denominator 1:500 or 1/500 A small scale map has a large denominator 1:250,000 A small scale map has a large denominator 1:250,000

A map with a scale of 1:10,000,000 would be considered when compared with a map of 1:1,000. A map with a scale of 1:10,000,000 would be considered small scale when compared with a map of 1:1,000. This is a small scale map – there is no detail shown. There is such great area – the whole earth – it must be small scale. i.e. 1 inch must be equal to millions of inches on the earth!

The Role of Globes A globe maintains correct geometric relationships A globe maintains correct geometric relationships But out of necessity is much smaller But out of necessity is much smaller A disadvantage is that it can be viewed only one half at a time. A disadvantage is that it can be viewed only one half at a time.

Map Projection Is a system based on mathematical computation that transforms the round surface of the Earth to display on a flat surface, i.e. a map. Is a system based on mathematical computation that transforms the round surface of the Earth to display on a flat surface, i.e. a map. It is impossible to portray a curved (3D) surface on a flat (2D) map It is impossible to portray a curved (3D) surface on a flat (2D) map There is always distortion There is always distortion There is NO perfect projection There is NO perfect projection

Map Projection A system based on mathematical computation A system based on mathematical computation It transforms the round surface of the Earth to display on a flat surface, i.e. a map. It transforms the round surface of the Earth to display on a flat surface, i.e. a map. Called ‘projection’ because it was originally a question of ‘projecting’ the grid (lat & long lines) onto a sheet of paper graphically.

Why Projections? The main objective is to preserve either the shape of the land or the area of the features - you can’t have it both ways! The following slides show different projections The following slides show different projections

Conic Projection Globe with light at center, projects images onto paper cone – when paper laid out flat, conic projection.

Plane Projection Globe with light at center, projects images onto adjacent paper plane (flat surface) – when paper is removed, you have: Azimuthal projection Plane projection Zenithal projection

Cylindrical Projection A globe with light in center projects onto paper cylinder – when paper laid flat, you have a cylindrical projection.

Equivalence vs. Conformality The central problem, when constructing a map is choosing the projection. The central problem, when constructing a map is choosing the projection. We must think about what is being shown; what part or how much of the earth is to be mapped? We must think about what is being shown; what part or how much of the earth is to be mapped? Equivalence = size Conformality = shape

Equivalence Equivalent projection is also called an equal area (size) projection Equivalent projection is also called an equal area (size) projection Misleading impressions of size are avoided Misleading impressions of size are avoided Good for showing distributions of geographic features Good for showing distributions of geographic features Problem: on small scale world maps shapes of land masses are disfigured Problem: on small scale world maps shapes of land masses are disfigured

Conformality Angular relationships are maintained Angular relationships are maintained Shape of land mass on map is same as shape on Earth Shape of land mass on map is same as shape on Earth All meridians and parallels cross at 90° angles – right angles. All meridians and parallels cross at 90° angles – right angles. Problem: the size of an area is considerable distorted to portray the proper shape. Problem: the size of an area is considerable distorted to portray the proper shape.

Mercator Projection Mercator Projection is a special purpose map projection used for navigation. is a special purpose map projection used for navigation. has area distortion has area distortion is conformal, i.e. preserves shape, not size is conformal, i.e. preserves shape, not size is the only map projection that shows true compass bearings for navigation is the only map projection that shows true compass bearings for navigation straight lines on a Mercator projection will always intersect longitude lines at the same angle - Mercator is the only map projection that does that. straight lines on a Mercator projection will always intersect longitude lines at the same angle - Mercator is the only map projection that does that.

MERCATORMERCATOR PROJECTIONPROJECTION

Conformal projection — preserves shapes Note the size of South America and Greenland South America = 17,819,000 sq km Greenland = 2,166,086 sq km

Mercator Conic Azimuthal How does North America compare between these three projections? Note how the lat-long lines are aligned in each of the projections.

Equal Area Projection Why is it used here? How do South America & Greenland compare in area? (p. 92)

Equal Area Projection (p. 2) Shows distribution of habitable and non-habitable land

Berghaus Star Equidistant, interrupted, modified azimuthal. Equidistant, interrupted, modified azimuthal. Viewed from the North Pole, the Northern Hemisphere is a polar Azimuthal Equidistant projection. The Southern Hemisphere is divided into five equal triangular lobes that are arranged in a star pattern around the Northern Hemisphere. Viewed from the North Pole, the Northern Hemisphere is a polar Azimuthal Equidistant projection. The Southern Hemisphere is divided into five equal triangular lobes that are arranged in a star pattern around the Northern Hemisphere. Used for the logo of the American Association of Geographers. Used for the logo of the American Association of Geographers.

Overlaying Maps If you could overlay one map on the other - the population map over the physical map - what would you be able to see? Is this a correlation? What kind of relationship does it describe? This is called spatial analysis

Isolines Any line that joins points of equal value of some feature Any line that joins points of equal value of some feature Some represent tangible features, i.e. elevation Some represent tangible features, i.e. elevation Some represent intangible features, i.e. temperature Some represent intangible features, i.e. temperature Some express relative values, i.e. proportions or ratios Some express relative values, i.e. proportions or ratios

Contour Line A line joining points of equal elevation 100 feet 50 feet

Contour Lines

Isobar A line joining points of equal atmospheric pressure

Isogonic Line A line joining points of equal magnetic declination

Isohyet A line on a map connecting points that receive equal precipitation. A line on a map connecting points that receive equal precipitation.

Isotherm A line joining points of equal temperature

Most Common Isolines Rainfall = Isohyets Temp = Isotherm Atm P = Isobars

Isolines do not occur in nature Isolines do not occur in nature They are artificial constructs They are artificial constructs Most important for patterns that are too large, too abstract, or too detailed for ordinary comprehension Most important for patterns that are too large, too abstract, or too detailed for ordinary comprehension They reveal and describe spatial relationships They reveal and describe spatial relationships

GIS - GPS – RS Geographic Information Systems Geographic Information Systems Global Positioning System Global Positioning System Remote Sensing Remote Sensing Geographic Information Technology - GIT

GIS Store, manipulate, retrieve, update and display data Store, manipulate, retrieve, update and display data Data is location or geographic data, i.e. it has a lat/long or is associated with a geographic region, which has a Data is location or geographic data, i.e. it has a lat/long or is associated with a geographic region, which has a

GPS A satellite based system that enables accurate positioning A satellite based system that enables accurate positioning Location determined by triangulation Location determined by triangulation Network of 24 high-altitude, earth orbital satellites Network of 24 high-altitude, earth orbital satellites 4 of these are always in view from anywhere on Earth 4 of these are always in view from anywhere on Earth Highly precise location data for any point on the planet, in any weather. Highly precise location data for any point on the planet, in any weather.

GPS can calculate positions accurate to a few meters. GPS can calculate positions accurate to a few meters. With advanced forms of GPS - to better than a centimeter With advanced forms of GPS - to better than a centimeter GPS is finding its way into cars, boats, planes, construction equipment, movie making gear, farm machinery, even laptop computers. GPS is finding its way into cars, boats, planes, construction equipment, movie making gear, farm machinery, even laptop computers.

Remote Sensing RADARSAT ScanSAR Narrow image shows flooded areas of North Carolina RADARSAT ScanSAR Narrow image shows flooded areas of North Carolina Final product shows flooded areas in light blue, rivers in dark blue, roads in red and coastline in green. Final product shows flooded areas in light blue, rivers in dark blue, roads in red and coastline in green.

Aerial Photographs Taken from an elevated platform, i.e. plane, rocket, satellite, etc. Taken from an elevated platform, i.e. plane, rocket, satellite, etc. Either oblique or vertical Either oblique or vertical Oblique shows features from a familiar point of view Oblique shows features from a familiar point of view Vertical gives precise measurement Vertical gives precise measurement

Vertical Aerial Photographs An advantage of vertical aerial photographs over oblique aerial photographs is that An advantage of vertical aerial photographs over oblique aerial photographs is that measurements of surface distances are usually easier

Overlapping Aerial Vertical Photographs Remote Sensing is any kind of recorded image captured by a device that is not in contact with the Earth

A reason for using color infrared photography versus conventional photography is that A reason for using color infrared photography versus conventional photography is that it shows differences in vegetation more accurately Color Infrared

Thermal Infrared Thermal infrared remote sensing is most widely used Thermal infrared remote sensing is most widely used for weather forecasting

The thematic mapper remote sensor is placed on The thematic mapper remote sensor is placed on Landsat Multispectral Scanning System - MSS