Topic 2: Portraying Earth: Using Maps, Remote Sensing and GIS Introduction to Maps: - What is a Map?...

Topic 2: Portraying Earth: Using Topic 2: Portraying Earth: Using Maps, Remote Sensing and GISMaps, 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

Incoming Solar Radiation:- Electromagnetic Spectrum- Insolation- Daily Insolation Pattern


- Map Projections:- Equivalent Projection- Conformal Projection

Remote Sensing:- Aerial Photographs- Orthophoto Maps- Visible light & Infrared Sensing- Thermal Infrared Sensing- Microwave Sensing


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?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?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?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 MapTopographic Map

Road Map

Geologic Map - Rock Types

Orthophoto Map from Aerial Photograph

USGS Topographic Map Quadrangle


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


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


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


Disadvantages of Maps: - Map distortions become progressively

pronounced as the part of the globe depicted gets larger

Introduction to Maps – Map ScaleIntroduction 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 ScaleTypes of Map Scale

Three Types of Map Scale

Three Types of 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


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)


Graphical or Bar Scale:

A scale shown as a line marked off in graduated distances


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 Introduction to Maps – Large and Small Scale MapsScale 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 MapsIntroduction 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 MapsDifferent Scales: From Small To Large Scale Maps

Small Scale

Large Scale Map


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 large-scale map

Introduction to Maps: Marginal Introduction to Maps: Marginal Information on MapsInformation 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


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


Some of these marginal information include:- Map title- Dates

- Legend

- Direction

- Scale

- Location

- Data Source

- Map projection, etc


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-of- date the information on the map is


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


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


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


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 ProjectionIntroduction to Maps: Map Projection

The Earth is spherical in shape as represented by the globe


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


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


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


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


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


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


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)


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 Map Projection -- conformal projectionconformal 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 Map Projection -- conformal conformal projectionprojection Continued 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 Map Projection -- conformal & Equal conformal & Equal Area projectionsArea projections

Map Projection Map Projection -- Equal-area Equal-area projectionprojection

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

Map Projection Map Projection -- Compromise Compromise ProjectionsProjections

Not purely conformal nor purely equivalent

Robinson’s Projection is in this category and ensures accurate shape and scale (size) representation


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: 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 Map Projections: Cylindrical Projection

It is produced by mathematically wrapping paper cylinder around the globe and touching the globe along the equator


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


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


Could show the map of the whole world but often cut off in the higher latitudes because of distortion issues


It preserves shapes (conformal) but distorts sizes on maps

Map Projections: Mercator Projection 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


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


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


Great Circle route on a spherical Earth surface


On Mercator Projection, the curved Great Circle approximated with four loxodromes

Map Projections: Plane Projection 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


Orthographic Plane Projection Showing Earth as it would appear from space

Map Projection – Conic ProjectionMap Projection – Conic Projection

It is a projection onto a cone surface with its apex placed above the pole


Latitudes are projected as concentric arcs of circles

Meridians are projected as straight lines radiating from the apex of the cone


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 distortion increases away from the apex of the cone

Conic Projector

Map Projection – Pseudocylindrical ProjectionMap 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


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


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

IsolinesIsolinesIsolines are lines joining places of equal valuesThere 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

IsolinesIsolines

- Isohyet: Line joining places with the same rain fall value or line of rain

IsolinesIsolines

IsolinesIsolines

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 SystemGPS: 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 accuracy may fall within ±15 metersWide 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 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: IntroductionRemote 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: IntroductionRemote 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 PhotographyRemote 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 PhotographyRemote Sensing: Aerial Photography

Remote Sensing: Orthophoto MapsRemote 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 & InfraredRemote Sensing: Visible Light & InfraredUses cameras with films sensitive to the

visible light or Infrared portions of the electromagnetic spectrum

Remote Sensing: Visible Light and Remote Sensing: Visible Light and Infrared SensingInfrared 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 Remote Sensing: Visible Light and Infrared SensingInfrared 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 Remote Sensing: Thermal Infrared Sensing?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 Remote Sensing: Multispectral Remote SensingSensing

Involves multiband sensing

Satellites equipped with instruments imaging at several regions of the electromagnetic spectrum simultaneously


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


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+)

Geographical Information System (GIS)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)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 vector-based (points, lines or polygon) data

It could be used to analyze both environmental and social processes

REVIEW QUESTIONS FOR TOPIC 2REVIEW 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 a1) 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.

Explanation: A verbal map scale tells you, with words, what the relationshipbetween area on the map and area on Earth is.

Figure 2-4

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 2) _____________ are automated systems for the capture, storage, retrieval, analysis, and displaycapture, storage, retrieval, analysis, and displayof spatially referenced data.of spatially referenced data.

A. Cartography

B. Geographic Information systems

C. Remote Sensing

D. Global positioning systems

E. Geomatic engineering

2) _____________ are automated systems for the 2) _____________ are automated systems for the capture, storage, retrieval, analysis, and displaycapture, storage, retrieval, analysis, and displayof spatially referenced data.of spatially referenced data.

Explanation: By definition, geographic information systems are computer-basedsystems which store, retrieve, analyze, and display spatial data.

Figure 2-29

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 3) Radar systems use radio waves as a means for remote sensing. Radio waves are shorter than remote sensing. Radio waves are shorter than which of these waves in the electromagnetic which of these waves in the electromagnetic spectrum?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 3) Radar systems use radio waves as a means for remote sensing. Radio waves are shorter than remote sensing. Radio waves are shorter than which of these waves in the electromagnetic which of these waves in the electromagnetic spectrum?spectrum?

Explanation: On the electromagnetic spectrum (Figure 2-22), radio waves have the longest wavelengths of all types of electromagnetic radiation.

Figure 2-22

A. isotherms.

B. isobars.

C. isohyets.

D. contour lines.

E. isogonic lines.

4) 4) IsolineIsoline is a generic term that refers to lines joining is a generic term that refers to lines joiningplaces of equal value or something. places of equal value or something. IsolinesIsolines joining places of equal elevation are known asjoining places of equal elevation are known as

Figure 2-15

A. isotherms.

B. isobars.

C. isohyets.

D. contour lines.

E. isogonic lines.

4) 4) IsolineIsoline is a generic term that refers to lines joining is a generic term that refers to lines joiningplaces of equal value or something. places of equal value or something. IsolinesIsolines joining places of equal elevation are known asjoining places of equal elevation are known as

Explanation: By definition, the lines of constant elevation on aelevation map are called contour lines.

Figure 2-15

A. conformal.

B. equivalent.

C. cylindrical.

D. Mercator.

E. isotropic.

5) Map projections that preserve the correct shapes 5) Map projections that preserve the correct shapes of places and compromise area are known asof places and compromise area are known as

Figure 2-7

A. conformal.

B. equivalent.

C. cylindrical.

D. Mercator.

E. isotropic.

5) Map projections that preserve the correct shapes 5) Map projections that preserve the correct shapes of places and compromise area are known asof places and compromise area are known as

Explanation: A map projection that maintains the correctshapes of geographic locations in exchange for preserving their size is called a conformal map projection.

Figure 2-7

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.

6) Globes are less frequently used than maps 6) Globes are less frequently used than maps except for classroom purposes. This is because except for classroom purposes. This is because globesglobes

Figure 2-6

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.

6) Globes are less frequently used than maps 6) Globes are less frequently used than maps except for classroom purposes. This is because except for classroom purposes. This is because globesglobes

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.

Figure 2-6

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 7) Which of the following is not an example of a remote sensing system?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 7) Which of the following is not an example of a remote sensing system?remote sensing system?

Explanation: Lambert-conformal maps are a special type of conformal map projection. As a result, they are not a type of remote sensing system.

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 you8) 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 you8) The map legend tells you

Explanation: Maps have many different components. The map legend gives you information about how to interpret colors, shapes, locations, etc. on a map.

Figure 2-5

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.

9) 9) Maps nearly always have a special purpose. Maps nearly always have a special purpose. This purpose is toThis purpose is to

Figure 2-2b

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.

9) 9) Maps nearly always have a special purpose. Maps nearly always have a special purpose. This purpose is toThis purpose is to

Explanation: A map’s purpose is to provide a spatial distribution of desired phenomena.

Figure 2-2b

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) 10) The global positioning system (GPS)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) 10) The global positioning system (GPS)The global positioning system (GPS)

Explanation: The GPS system is a remote sensing system that is used to identify locations on Earth based on latitude and longitude.

Figure 2-19

Topic 2: Portraying Earth: Using Maps, Remote Sensing and GIS Introduction to Maps: - What is a Map?...

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Transcript of Topic 2: Portraying Earth: Using Maps, Remote Sensing and GIS Introduction to Maps: - What is a Map?...