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GEOG 2240A/B (14)

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Lecture

# Geography 2240A/B Lecture Notes - Times New Roman, Main Source, Corel

14 pages64 viewsWinter 2014

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**preview**shows pages 1-3. to view the full**14 pages of the document.**Lecture 1

Objectives

1. How to produce maps

•To illustrate reports and papers

2. How maps are made

•To help understand them (e.g. more skeptical about contours after you have drawn some)

•To understand their possibilities and limitations

3. Some basic computer graphic skills

•Background for other courses in remote sensing, GIS

•Preparation of web graphics

Cartography

-Definition:

oThe art and science of making maps

-Art:

oDesign:

Aesthetics – For an attractive map

Functionality – For a useful map

oCreativity

Cartographers have to follow certain conventions

But there is still room for individuality, creativity

-Science:

oSurveying – Accurate measurement of location

oData collection – Contents of the map

oPerception – How we extract information from a map

-History of cartography:

oA major area of study itself

Maps

-Definition:

o“…graphic representations that facilitate a spatial understanding of things, concepts, conditions,

processes or events…”

o(from Harley, J.B. and Woodward, D., The History of Cartography, Vol. 1)

oMany textbooks give inadequate definitions, biased towards modern geographic maps

-Plans and charts:

oNo different from maps

oPlan – Usually refers to a map of a small object like a building, room or even a machine

oChart – Usually refers to a map used for navigation

oBut they are both just types of map. The distinction is arbitrary and unnecessary

Coordinates

Location On The Earth

-Coordinate reference points:

oEarth is nearly spherical (within 0.5%)

oAssume it is a perfect sphere

oEarth rotates around its axis of rotation

oMain reference line for coordinates

oMeets surface at north and south poles

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oEquator defined by plan perpendicular to axis, passing through the planet’s centre

-Latitude

oAngular distance north or south from equator to poles

oGeocentric Latitude – Angle between the equatorial plane and radius (centre of Earth to a point)

oGeographic Latitude – Angle between the equatorial plane and vertical line at a point

-Longitude

oMeasured east or west from a meridian (line from pole to pole)

oInternational convention: Prime meridian runs through the Greenwich Observatory in London,

England

oMeasured 180 degrees to East and West (rarely: 360 degrees around the globe, east from the prime

meridian)

oTwo angles, latitude N or S of the equator and longitude E or W from the prime meridian, define a

position on the globe

Location On A Map

-Latitude and longitude:

oGrid drawn on map or marked along the edges

oE.g. A point is at 45 degrees, 50 minutes 22 seconds north, and 78 degrees, 20 minutes, 10 seconds

west

oWritten as: 45° 50’ 22” N, 78° 20’ 10” W

oCheck out this link for more information:

http://www-istp.gsfc.nasa.gov/stargaze/Slatlong.htm

-Universal Transverse Mercator (UTM) grid (military grid)

oUniversal – Covers the whole world

oTransverse Mercator – Map projection it is based on

oSquare grid, 1km spacing

oDrawn in long narrow strips (zones) – Total of 60 zones

oEach zone covers 80° N to 80° S, only 6° of longitude wide

oPoles mapped separately with a grid centred on the pole

oCheck out this link for more information:

http://geology.isu.edu/geostac/Field_Exercise/topomaps/utm.htm

-Grid reference:

oLike stating x-y coordinates on a graph

oEdges of map are labelled like axes of a graph

oGive Easting – Distance in east-west direction, estimated to a tenth of a grid square (100m for a

1km grid)

oGive Northing – Distance north-south estimated to 1/10 square

Example: 43.7 easting, 55.3 northing, written as 427553

oBut note that this is an abbreviated grid reference, just used for convenience. 100km north or east of

here would be another place with the same numbers. The full reference avoids this – see link below.

A full grid reference tells us which zone we are in and gives unambiguous coordinates, as in the

linked example

oCheck this link for more information:

http://maps.nrcan.gc.ca/topo101/utm_references_e.php

-Arbitrary grid of letters or numbers

oCommon on street maps

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Lecture 2

Map Scale, Directions

Scale

-Precise geometric relationship between a map and the region it portrays

oOne of the most important characteristics of a modern map

oMost maps are greatly reduced in size compared to their subjects, so scale is a small fraction

-Definition:

oRatio of the size of the map to its subject

oScale = Distance on a map / distance on the ground

-Example:

oTwo points on the ground are 1000m apart

oRepresented on the map by points only 1cm apart

oCalculate scale as follows:

1cm represents 1000m

1000m = 100,000cm

So 1cm represents 100,000cm

So scale = 1cm / 100,000cm = 1/100,000

-Scale is a fraction expressed in 3 ways:

oRepresentative Fraction (RF) – E.g. 1 : 100,000

oVerbal Scale – ‘One cm represents one km’

oGraphic Scale – A line labeled with the distance it represents

-Graphic scale remains accurate if map is enlarged or reduced. Verbal ad RF scales do not

-On a graphic scale, the intervals must be convenient round numbers

Scale Examples

-Example: Ground distance = 5 km, map distance = 2 cm

oStep 1: 2 cm represents 5 km (write in full)

oStep 2: 1 cm represents 2.5 km (divide so left side = 1)

oStep 3: 1 cm represents 250,000 cm (convert to same units)

oStep 4: Scale is 1: 250,000 (express as a representative fraction)

-Example: Distance on map = 3.5 cm, map scale = 1: 15,000

oWhat is the real distance?

oStep 1: 1 cm represents 15,000 cm (express scale in words, same units as your measurement)

oStep 2: 3.5 cm represents (3.5 x 15,000) cm = 52500 cm (multiple both sides by map distance)

oStep 3: 3.5 cm represents 525 m (convert to more convenient units)

oAnswer: 525 m

Scale

-Large and small scales:

oScale is a fraction

o½ is larger than ¼

o1/5000 is larger than 1/100,000

o1: 5000 is a larger scale than 1: 100,000

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