Topic 2: Portraying Earth: Using
Maps, Remote Sensing and GIS
 Introduction
-
to Maps:
What is a Map?
Benefits of Maps
Marginal information on Maps
Map Scale
Map Projections:
- Cylindrical Projections
- Plane Projection
- Conic Projection
Topic 2: Portraying Earth: Using
Maps, Remote Sensing and GIS
- Map Projections:
- Equivalent Projection
- Conformal Projection
 Remote Sensing:
- Aerial Photographs
- Orthophoto Maps
- Visible light & Infrared Sensing
- Thermal Infrared Sensing
- Microwave Sensing
Topic 2: Portraying Earth: Using
Maps, Remote Sensing and GIS

Remote Sensing:
- Microwave Sensing
- Multispectral Remote Sensing
 Geographic Information Systems (GIS)
- What is GIS
- GIS Automation Tools
 Isolines and Applications
Introduction to Maps: What is a Map?
 Geographic
information describing
earth’s surface features are often
displayed by geographers on:
- maps: examples include road map,
topographic map, surveyor’s map, etc)
- aerial photographs
- satellite imageries
- GIS, etc
Introduction to Maps: Benefits of Maps?

A map is a two-dimensional
representation of the spatial distributions
of features of interest in a place or region
 Maps
show spatial relationships between
features, especially:
- direction
- distance
- size and shape
Introduction to Maps: What is a Maps?

May provide clue why things are located
where they are
 The main purpose of maps is to show the
spatial distribution of one or more
features of interest
Orthophoto Map
Topographic Map
Geologic Map - Rock Types
Road Map
Orthophoto Map from Aerial Photograph
USGS Topographic Map Quadrangle
Introduction to Maps: Benefits of Maps?
 Benefits
-
-
of Maps:
Map is the geographer’s most important
tool
Represents earth’s features on a flat
paper
it shows spatial relationships with great
efficiency
It can show true courses for navigation
and true shapes of earth’s features
Introduction to Maps: Benefits of Maps?
 Benefits
-
-
of Maps:
It can be used to measure areas and
distances
It can be reproduced easily and
inexpensively
It is easier to handle and transport
It is often smaller than the areas they
represent and contains less details
Introduction to Maps: Benefits of Maps?
 Benefits
of Maps:
- The accuracy and amount of
information contained in a map will
depend on its scale and projection
 Disadvantages
of Maps:
- It distorts the earth in some ways, hence
could not depict the earth with complete
accuracy
Introduction to Maps: Benefits of Maps?
 Disadvantages
of Maps:
- Map distortions become progressively
pronounced as the part of the globe
depicted gets larger
Introduction to Maps – Map Scale
Map Scale:

Scale is a mathematical expression or
statement of a relationship between distances
or sizes on map and their actual measurements
on the ground

Types of scale:
1. Statement Scale or Verbal or Word Scale
2. Fractional Scale and
3. Graphical Scale
Types of Map Scale
Three Types of Map Scale
Three Types of Map Scale
Introduction to Maps – Map Scale
Map Scale:
 Statement Scale or Verbal or Word Scale
A scale stating in words the distance on map
compared to the actual distance on the ground
Example: one inch on the map represents one
mile on the ground or 1 inch = 1 mile)

Representative Fraction or Ratio Scale
A scale in which map distance is represented
as a proportional number of its actual distance
on the ground
Introduction to Maps – Map Scale
Example: 1:63360 or 1/63360, meaning a
unit length on the map equals 63360 units on
the ground
-
Common Ratio Scales used on maps:
a. world map (1:264,000,000)
b. road map of a state (1:1,000,000
to 1:2,000,000)
c.
street map of a city (1:10,000)
d. residential lot (1:100)
Introduction to Maps – Map Scale

Graphical or Bar Scale:
A scale shown as a line marked off in
graduated distances
Introduction to Maps – Map Scale

Graphical or Bar Scale:
A major advantage is that it remains valid when
map is reduced into another size (through
photocopying) because the graphical scale line
and map size change in same dimension
Introduction to Maps – Large and Small
Scale Maps
 Two types of maps based on map scale are:
- Small-Scale Maps
- Large-Scale Maps

Small-scale maps show large portions of the
earth cramped into a small paper

It is indicated by a map scale with a large
denominator (1/1,000,000)

Examples of small-scale maps: World map, US
Map
Introduction to Maps – Large and Small Scale Maps
Introduction to Maps – Large and Small Scale Maps
Introduction to Maps – Large and Small
Scale Maps
 Large-scale
maps show a very small area
of the earth in a large space
 It
is indicated by a map scale with a
small denominator (1/100)
 Examples
of large-scale maps:
- a house plan
- a school map
Different Scales: From Small To Large Scale Maps
Small Scale
Large Scale Map
Introduction to Maps – Large and Small
Scale Maps
 Class
Practice Exercises:
 convert
a statement scale (1inch = 2400
feet) to:
- a fractional scale
- a graphical scale
 List
three maps you consider to be a largescale map
Introduction to Maps: Marginal
Information on Maps

Maps are drawn for different purposes:
- general purpose maps (e.g. world map)
- thematic maps showing distribution of a
specific phenomenon(population density)
-
In general, maps contain useful
information to help in map interpretation
-
Most of such useful information are often
shown on the margins of the map
Introduction to Maps: Marginal
Information on Maps

Maps are drawn for different purposes:
- general purpose maps (e.g. world map)
- thematic maps showing distribution of a
specific phenomenon(population density)

In general, maps contain useful information to
facilitate their use and interpretation

Most of such useful information are often
shown on the margins of the map
Introduction to Maps: Marginal
Information on Maps

Some of these marginal information include:
- Map title
- Dates
- Legend
- Direction
- Scale
- Location
- Data Source
- Map projection, etc
Introduction to Maps: Marginal
Information on Maps

Map Title:
- It usually should reflect map content or
purpose and identifies the area covered (e.g.
Road Map of St. Louis)

Date:
- Date of data collection and publication gives
clear indication of how current or out-ofdate the information on the map is
Introduction to Maps: Marginal
Information on Maps

Legend:
- Often shown as a box explaining symbols
used on the map
-

Symbols, colors, shadings used in
representing features on the map explained
Direction:
- Directions are indicated using geographic
grids (e.g. latitude and longitude) and north
pointing arrow
Introduction to Maps: Marginal
Information on Maps

Direction:
- The north arrow points at the Geographic
(True) North Pole
- The Magnetic North Pole is the direction a
magnetic compass points

Location:
- Longitude and latitude coordinates are
useful for locating places on maps
Introduction to Maps: Marginal
Information on Maps

Map Scale:
- Gives the relationship between length
measures on the map and the
corresponding distance on the ground
-
Map scale helpful when measuring
distances between points or calculating the
area occupied by any geographic feature on
map
Introduction to Maps: Marginal
Information on Maps

Data Source:
- Information on data source is important in
establishing credibility of the final map
-
It indicates the level of data quality and
accuracy
Introduction to Maps: Map Projection
 The
Earth is spherical in shape as
represented by the globe
Introduction to Maps: Map Projection
 The
globe accurately represents the shape
of our planet
 It is useful in maintaining the geometric
relationships of:
- longitudes to latitudes
- equator to the poles
- continents to oceans
 It can also maintain correct:
- comparative distances
Introduction to Maps: Map Projection
 Without
distortion, the globe can also
maintain correct:
- comparative sizes and
- directions
 But the globe has its own problems:
- only half of the globe can be viewed at
a time
- only very little details can be displayed
on a globe
Introduction to Maps: Map Projection
 But
the globe has its own problems:
- globes are cumbersome to use and
difficult to handle or carry around
- computations on globe surfaces
require complex and difficult
equipment and techniques
- globe construction is labor-intensive
and costly
Introduction to Maps: Map Projection
 In
order to overcome some of the
problems of working with the globe, flat
maps are preferred because:
- flat maps are portable
- less expensive to reproduce
- easy to work with
 But this comes with some costs and
disadvantages that include:
- it may lead to geometric distortions
Introduction to Maps: Map Projection
 But
this comes with some costs and
disadvantages that include:
- violation of the continuity of the earth
surface
- distortion of reality
- no true solutions to these problems
hence all maps are not perfect
Introduction to Maps: Map Projection
 Maps
are flat whereas the Earth is
spherical in shape
 To
produce a map, we need to transfer
location information on spherical earth
surface to their appropriate locations on a
flat map
Introduction to Maps: Map Projection
 The
map projection process results in the
distortion of four attributes of places on
the globe:
-
distance between points
place orientation or direction
actual shape
actual size (i.e. area)
Introduction to Maps: Map Projection

The distortion problem progressively
increases with the size of the globe
being represented on a flat map
 Common methods of map projections
involves deliberate effort to preserve:
- Conformal Projection
(shape & direction preservation)
- Equal-area or Equivalent Projection
(size or area preservation)
Preserves Area or Size
Preserves Shapes
Map Projection - conformal projection

It distorts size but preserves shape (or
orientation)

Angular relationships are maintained
such that shape of any geographic
feature is the same as observed on the
spherical earth

Meridians and parallels cross at right
angles
Map Projection - conformal
projection Continued

Sizes of geographical features become
progressively larger towards the
higher latitudes (hence Greenland
appears bigger than necessary)

A good example is the Mercator
projection (directions remain constant
and rectangular shape fits a flat map
model
Map Projection - conformal & Equal
Area projections
Map Projection - Equal-area
projection

It preserves size but distorts shape and
avoids misleading impressions of size

Great for showing distributions of
geographic features

Shapes are sacrificed in order to maintain
proper area relationships

Example: Lambert’s equal-area projection
Compromise
Projections
Map Projection 
Not purely conformal nor purely
equivalent

Robinson’s Projection is in this category
and ensures accurate shape and scale (size)
representation
Introduction to Maps: Map Projection

involves deliberate effort to preserve:
- Compromise Projection
(not truely conformal nor equivalent)

Preservation of one geometric property
may lead to the distortion of another

Hence, not all distortions can be
controlled on a single map
Compromise Projection Between
Conformal and Equivalence
Map Projections:

Types of Map Projections:
- Cylindrical Projections
- Plane Projection
- Conic Projection
- Pseudocylindrical Projection

Projection type based on main source of light:
- gnomonic projection (center light source)
- orthographic projection (outside the earth)
- stereographic projection (earth surface light)
Map Projections: Cylindrical Projection

It is produced by mathematically wrapping
paper cylinder around the globe and
touching the globe along the equator
Map Projections: Cylindrical Projection

This is called equatorial tangency which
helps to produce:
- right-angled grid network which become
rectangular grids on flat maps
- no distortions (e.g. size) along the circle of
equatorial tangency
- but distortion increases poleward, hence
Greenland & Antarctica are larger than
normal
Map Projections: Cylindrical Projection
Map Projections: Cylindrical Projection

Circle of tangency outside the equator are
also used

Mercator projection is a good example of a
cylindrical projection

Other examples of cylindrical projections:
- Gall’s stereographic cylindrical projection
- Lambert’s cylindrical Equal area
Projection
Map Projections: Cylindrical Projection

Could show the map of the whole world but
often cut off in the higher latitudes because
of distortion issues
Map Projections: Cylindrical Projection

It preserves shapes (conformal) but distorts
sizes on maps
Map Projections: Mercator Projection

Developed in 1569 and remains the most
famous of all projections

Originally designed to facilitate navigation
by sailors

It is a conformal projection, hence:
- preserves shapes
- size distortion increases rapidly poleward
Map Projections: Mercator Projection

It keeps the meridians parallel to one another
instead of converging at the poles

This causes east-west stretching such that area
or size is exaggerated by four times at lat. 60o
and thirty-six times at lat. 80o

To maintain conformity, latitudes were spaced
increasingly using mathematical formula to
keep north-south stretching uniform
Map Projections: Mercator Projection


It shows loxodrome or rhump line as straight
line
A loxodrome is a straight line anywhere on a
map and in any direction oblique to the grid
lines and maintain a constant compass
direction
Light source at the globe centre
Map Projections: Mercator Projection

Great Circle route on a spherical Earth surface
Map Projections: Mercator Projection

On Mercator Projection, the curved Great Circle
approximated with four loxodromes
Map Projections: Plane Projection

It is also called azimuthal projection or zenith
projection

It is a projection of the Earth on a flat paper placed
on any point of the globe though polar tangency is
common

Distortion increases away from point of tangency

No more than half of the globe can ne displayed
Map Projections: Plane Projection
Map Projections: Plane Projection
Orthographic Plane Projection Showing Earth as
it would appear from space
Map Projection – Conic Projection

It is a projection onto a cone surface with
its apex placed above the pole
Map Projection – Conic Projection


Latitudes are projected as concentric arcs
of circles
Meridians are projected as straight lines
radiating from the apex of the cone
Map Projection – Conic Projection

Only one-fourth of Earth’s surface can be
projected at a time

Best for mapping relatively small areas
with great east-west extent

Useful for mapping the United States,
China and other areas in the mid-latitudes
Map Projection – Conic Projection

Map distortion increases away from the
apex of the cone
Conic Projector
Map Projection – Pseudocylindrical Projection

It is also called:
- elliptical projection
- oval projection

Used in mapping the entire globe

But smaller areas could be mapped if
located at the central parallel meeting the
central meridian with the least distortion
Map Projection – Pseudocylindrical Projection

Final maps look oval in shape and meridians
converge at the pole

The meridians are curved except for the
central meridian that drawn as straight line

Goode’s interrupted homolosine projection
is a good example

It is equivalent projection
Map Projection – Pseudocylindrical Projection

But also maintains the shapes of continental
coastlines

Projection is interrupted in the oceans to
greatly reduce shape and size distortions
It distorts shapes of areas in the high
latitudes


Hence, Goode splits his map in the southern
oceans at selected meridians
Isolines

Isolines are lines joining places of equal values
 There are many types of Isolines:
-
-
Isobar: Line joining places with the same
pressure value or line of constant pressure
Isotherm: Line joining places with the same
temperature value or line of constant
temperature
Isoamplitude: Line joining places with the
same wave amplitude or line of constant
wave amplitude
Isolines
-
Isohyet: Line joining places with the same
rain fall value or line of rain
Isolines
Isolines
Isolines

Isoline joining places of
the same elevation is
called contour line

Very closely spaced
contours represent
steeper terrains

Widely spaced contours
represent gentle to flat
terrains
GPS: Global Positioning System

GPS is global navigational satellite system for
determining the location of a place

Developed in the 1970s and 1980s by the US
DOD and once called NAVSTAR GPS
(Navigation Signal Timing and Ranging GPS)

It consists of at least 24 high-altitude satellites
with a minimum of four to six in view at any
location
GPS: Global Positioning System
GPS: Global Positioning System

GPS accuracy may fall within ±15 meters
 Wide Area Augmentation System (WAAS) has
significantly improved GPS accuracy to ±3
meters

WAAS ground-based stations monitor satellite
signals & generate correction signal to GPS units.

NOAA Continuously Operating GPS Reference
Stations (CORS) detect location changes of <1cm
GPS: Global Positioning System

GPS applications include:
-
earthquake forecasting
ocean floor mapping and mapping in general
volcanic monitoring
data collection and damage assessment
navigation GPS in vehicles
military uses, etc
Remote Sensing: Introduction

Remote sensing is the collection of data about
an object by a device not in direct contact with
the object

Common types of remote sensing include:
- Aerial photographs
- Orthophoto maps
- Visible light and Infrared (IR) Scanning
- Thermal IR scanning
- Radar and Sonar, etc
Remote Sensing: Introduction

Remote sensing originally involved the use of
airplanes but today 100s of satellites are used

Satellites in low orbits of less than 20,000km
orbit the earth taking photographs

Satellites on geosynchronous orbit (36,000km)
remain in one spot to gather data
Remote Sensing: Aerial Photography

Aerial photograph taken for some height above
the ground using:
- balloons (France 1858 & USA 1860)
- airplane (as from WW1 1914-1918)
- rockets

Based on camera angle, aerial photographs are
classified as:
- vertical (great for precise measurement)
- oblique (measurement is more difficult)
Remote Sensing: Aerial Photography
Remote Sensing: Orthophoto Maps

Orthophoto maps are derived from aerial
photographs and images

Distortions caused by camera tilt and difference
in ground elevation are removed

Shows landscapes in greater details, multicolored;
and great for showing low-lying areas

Georeferenced; distance measurement is possible
ORTHOPHOTO MAP
Remote Sensing: Visible Light & Infrared
 Uses
cameras with films sensitive to the
visible light or Infrared portions of the
electromagnetic spectrum
Remote Sensing: Visible Light and
Infrared Sensing
 Conventional
photographic films were
only sensitive to visible light but other
wavelengths could produce more
information omitted by visible light
 During
WWII Infrared sensing using
electronic sensors or films sensitive to
near infrared wavelength was introduced
Remote Sensing: Visible Light and
Infrared Sensing
 IR
imagery produces false-color images
such that:
- healthy vegetation is red
- bare ground is gray-blue
 IR
imagery is useful for the identification
and evaluation of vegetation
Remote Sensing: Thermal Infrared
Sensing?
 Involves
the use of middle or far infrared
portion of the spectrum called thermal IR
 Useful
for sensing:
- temperature of objects
- forest fires
- weather parameters (e.g. GOES
Weather satellites)
Remote Sensing: Multispectral Remote
Sensing
 Involves
multiband sensing
 Satellites
equipped with instruments
imaging at several regions of the
electromagnetic spectrum simultaneously
Remote Sensing: Multispectral Remote
Sensing
 Examples
of multispectral Sensing
systems:
- Landsat
- SPOT
- IRIS
 Landsat:
- launched a four-band multispectral
Scanning System (MSS) with a scene of
115 by 106 miles
Remote Sensing: Multispectral Remote
Sensing
 Landsat:
- launched Landsat 4 and 5 in early
1980s with seven-band Thematic
Mapper (TM) of 30m by 30m pixels
- Launched Landsat 7 in 1999 with
eight-band Enhanced Thematic
Mapper plus (ETM+)
Remote Sensing: Multispectral Remote
Sensing
Remote Sensing: Multispectral Remote
Sensing
Geographical Information System (GIS)

It is a database management system that
facilitates the collection, analysis and
display of geographic data

Owes its origin to a group of new
computer-based technologies developed in
surveying, photogrammetry, cartography,
spatial statistics, and remote sensing

It has the ability to accept digital satellite
imageries and other data sources
Geographical Information System (GIS)

It stores the geo-referenced data and
integrates multi-layers of attributes of
a place into a single usable map

GIS accepts both raster-based
(rectangular grid cells) and vectorbased (points, lines or polygon) data

It could be used to analyze both
environmental and social processes
REVIEW QUESTIONS FOR TOPIC 2
1) A map scale which says “1 in. = 21 mi” is a
A. divisional map scale.
B. fractional map scale.
C. graphic map scale.
D. verbal map scale.
E. orthonormal map scale.
1) A map scale which says “1 in. = 21 mi” is a
A. divisional map scale.
B. fractional map scale.
C. graphic map scale.
D. verbal map scale.
E. orthonormal map scale.
Figure 2-4
Explanation: A verbal map scale tells you, with words, what the
between area on the map and area on Earth is.
2) _____________ are automated systems for the
capture, storage, retrieval, analysis, and display
of spatially referenced data.
A. Cartography
B. Geographic Information
systems
C. Remote Sensing
D. Global positioning systems
E. Geomatic engineering
Figure 2-29
2) _____________ are automated systems for the
capture, storage, retrieval, analysis, and display
of spatially referenced data.
A. Cartography
B. Geographic Information
systems
C. Remote Sensing
D. Global positioning systems
E. Geomatic engineering
Figure 2-29
Explanation: By definition, geographic information systems are
systems which store, retrieve, analyze, and display spatial data.
3) Radar systems use radio waves as a means for
remote sensing. Radio waves are shorter than
which of these waves in the electromagnetic
spectrum?
A. Microwaves
B. X-rays
C. Visible waves
D. Infrared waves
E. Radio waves are
the longest waves
3) Radar systems use radio waves as a means for
remote sensing. Radio waves are shorter than
which of these waves in the electromagnetic
spectrum?
A. Microwaves
B. X-rays
C. Visible waves
D. Infrared waves
E. Radio waves are
the longest waves
Figure 2-22
Explanation: On the electromagnetic spectrum (Figure 222), radio waves have the longest wavelengths of all types of
4) Isoline is a generic term that refers to lines joining
places of equal value or something. Isolines
joining places of equal elevation are known as
A. isotherms.
B. isobars.
C. isohyets.
D. contour lines.
E. isogonic lines.
Figure 2-15
4) Isoline is a generic term that refers to lines joining
places of equal value or something. Isolines
joining places of equal elevation are known as
A. isotherms.
B. isobars.
C. isohyets.
D. contour lines.
E. isogonic lines.
Figure 2-15
Explanation: By definition, the lines of constant elevation on a
elevation map are called contour lines.
5) Map projections that preserve the correct shapes
of places and compromise area are known as
A. conformal.
B. equivalent.
C. cylindrical.
D. Mercator.
E. isotropic.
Figure 2-7
5) Map projections that preserve the correct shapes
of places and compromise area are known as
A. conformal.
B. equivalent.
C. cylindrical.
D. Mercator.
E. isotropic.
Figure 2-7
Explanation: A map projection that maintains the correct
shapes of geographic locations in exchange for preserving their
size is called a conformal map projection.
6) Globes are less frequently used than maps
except for classroom purposes. This is because
globes
A. are illegible compared to maps.
B. are hard to read.
C. are cumbersome.
D. do not maintain the correct
geometric relationship between
locations.
E. are inaccurate when compared
to maps.
Figure 2-6
6) Globes are less frequently used than maps
except for classroom purposes. This is because
globes
A. are illegible compared to maps.
B. are hard to read.
C. are cumbersome.
D. do not maintain the correct geometric
relationship between locations.
E. are inaccurate when compared to
maps.
Figure 2-6
Explanation: Globes have many advantages and
disadvantages. They maintain the correct geometric locations
of places on Earth, but are large and bulky, making them
inconvenient for settings outside of a classroom.
7) Which of the following is not an example of a
remote sensing system?
A. Satellites
B. Radar
C. Global positioning system
D. Aerial photography
E. Lambert-conformal maps
7) Which of the following is not an example of a
remote sensing system?
A. Satellites
B. Radar
C. Global positioning system
D. Aerial photography
E. Lambert-conformal maps
Explanation: Lambert-conformal maps are a special type of
conformal map projection. As a result, they are not a type of
remote sensing system.
8) The map legend tells you
A. the history of the map.
B. what direction is north.
C. the map projection.
D. how to interpret the
map.
E. latitude and longitude.
8) The map legend tells you
A. the history of the map.
B. what direction is north.
C. the map projection.
D. how to interpret the
map.
E. latitude and longitude.
Figure 2-5
Explanation: Maps have many different components. The map
legend gives you information about how to interpret colors,
shapes, locations, etc. on a map.
9) Maps nearly always have a special purpose.
This purpose is to
A. show the exact size and height of
physical features.
B. represent an enlargement of a
section of Earth.
C. resolve misunderstandings
regarding positional relationships
on Earth’s surface.
D. show as much spatial information
as the paper can possibly hold.
E. show the distribution of selected
phenomena.
Figure 2-2b
9) Maps nearly always have a special purpose.
This purpose is to
A. show the exact size and height of
physical features.
B. represent an enlargement of a
section of Earth.
C. resolve misunderstandings
regarding positional relationships
on Earth’s surface.
D. show as much spatial information
as the paper can possibly hold.
Figure 2-2b
E. show the distribution of
selected phenomena.
Explanation: A map’s purpose is to provide a spatial
distribution of desired phenomena.
10) The global positioning system (GPS)
A. uses satellite measurements
to provide navigation on
Earth’s surface.
B. is based off of radar.
C. only works in urban areas.
D. provides location based on
miles from a major city.
E. allows for the layering of maps
on each other.
10) The global positioning system (GPS)
A. uses satellite measurements
to provide navigation on
Earth’s surface.
B. is based off of radar.
C. only works in urban areas.
D. provides location based on
miles from a major city.
E. allows for the layering of maps
on each other.
Figure 2-19
Explanation: The GPS system is a remote sensing system that
is used to identify locations on Earth based on latitude and
longitude.