Geographic Information Systems (GIS) in Planning and ...

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Geographic Information Systems (GIS)in Planning and Resource Management

ENVS 6189 3.0 - lecture 2

John Sorrell

York University. [email protected]

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Consolidated Consolidated Definition:Definition:

GIS in Environmental Studies

measurementrepresentationoperations

transformations

institutional context

social and cultural context

Geographic Information System – An organized activity by which people measure and represent geographic phenomena then transform these representations into other forms of information while interacting with social structures

- Chrisman 2002.

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Session Purpose:Session Purpose:

To introduce the various types of map representations, cartographic elements, and geo-referencing mechanisms used to prepare data for use in geographic information systems.


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History of Map History of Map Making:Making:

Evidence of map making suggests maps evolved independently in various times, cultures and locations on the Earth.

Babylonian cuneiform tablet – 1400 B.C.


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History of Map History of Map Making Making (cont’d)(cont’d): :

“The Character and Technology of mapmaking may have changed… but the potential of maps has not. Maps embody a perspective of that which is known and a perception of that which may be worth knowing.”

John Noble Wilford


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Cartography as Cartography as Communication:Communication:

-Maps represent a deposit of geographic knowledge;

-Cartography is the art and science that deals with the construction, use and principles of map design;

- Keith Clarke, draw on analogies between cartographic communication and language (use of grammar and syntax as a rule system to convey a clear message);

- Basic principles of cartography are required (production & end-user perspective).


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Cartographic Cartographic Abstraction:Abstraction:

Maps are abstractions or generalizations of reality.

Cartographic Abstraction: 1) Selection2) Simplification3) Exaggeration 4) Symbolization5) Classification

Distortion vs. Precision = Paradox

Mark Monmonier


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Type of Maps in Type of Maps in GIS:GIS:

Generally two (2) types of maps used:

Topographical (reference) : convey the outlines of selected natural and built features of the Earth. Topographical refers to the shape of the surface, represented by contours and/or shading.


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Thematic (special purpose) : Conveys statistical concepts such as distribution or density across space.

Type of Maps in Type of Maps in GIS GIS (cont’d)(cont’d)::

Types of Thematic map:

Choropleth – Boundaries of zones are determined independently from the data;

Area Class – Boundaries are determined from the spatial configuration of phenomenon under scrutiny;

Isopleth – Shows a surface by means of lines of equal values (isolines) to display a trend or distribution across space.


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Basic Map Basic Map Elements:Elements:

• Title• Legend• Direction * Scale• Source * Symbolization • Neat line• Date of Production• Body of Map• Supplementary Material


>Overhead

Bunch, M (2002) "Cartographic Conventions" York University.

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Scale (spatial):Scale (spatial):

All maps are smaller than the reality they represent.

• 3 types: Ratio Scale 1:20,000Verbal Scale “inch to the mile”Graphic Scale


1:1000 1:50,000 1:1,000,000large scale medium scale small scale

Temporal scale: more measures of Ti, the higher the temporalresolution and finer the temporal scale

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Symbolization:Symbolization:

Graphic symbols complement map scale and projection by making visible the features and location information represented on the map.

Logic of Map Symbols & Design:

- Geometric & Visual Variables- Shading and Hatching- Colour and Cultural Conventions


>Overhead

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Basic Coordinate Basic Coordinate Systems: Systems:

A coordinate is one of a set of numbers that determines the location of a point in space ofa given dimension.


Two (2) basic types of coordinatesystems on a plane (2-D) surface:

- Plane Rectangle;- Plane Polar.

P

X- X

-Y

Y + X+ Y

- X+ Y

- X- Y

+ X- Y

O M

N

>Overhead

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Basic Coordinate Basic Coordinate Measurement Systems: Measurement Systems:

A coordinate is one of a set of numbers that determines the location of a point in space ofa given dimension.


Two (2) basic types of coordinatesystems on a plane (2-D) surface:

- Plan Rectangle; - Plane Polar.

P

X- X

-Y

Y

O M

N

rθ

(r, θ)

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Typical Coordinate Typical Coordinate Systems in GIS:Systems in GIS: Numeric methods of representing

locations on the Earth’s surface.

1) Geographic - GCS (Spherical)- Latitude (parallels) Longitude (meridians) where Equator and

Prime Meridian are used as standard reference lines to form a network (graticule).


EW

The position of a point isdetermined by two anglesof planes that intersect withthe Origin

>Overhead

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Map Projection:Map Projection:

A Map projection can distort four geographic relationships: Area, Shape, Distance, and Direction

Mercator Projection

A projection is identified by the relationship it preserves.


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Typical Coordinate Typical Coordinate Systems in GIS:Systems in GIS:

Numeric methods of representing locations on the Earth Surface.

2) Projected UTM- Universal Transverse Mercator (UTM Grid)- local or regional geo-referencing system using a Cartesian

rectangular coordinate system.- 60 grid cells measuring 6 degrees in longitude width and 8

degrees in latitude height

GIS in Environmental Studies>Overhead

• The projection is repeated at 6 degree intervals;• Projection zones are limited at 84 ° N and 80 ° S• other measures have been taken to minimize distortion of scale

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Geodetic and Vertical Geodetic and Vertical DatumsDatums: :


• Earth’s shape is not a perfect sphere but is highly irregular;

• The ellipsoid-geoid model is the most commonly used mathematical surface to represent the shape of the Earth.

A Datum is a model that describes the position, direction and scale of a reference system to positions on the Earth’s surface (Lo & Yeung 2002).

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Geographic Geographic Referencing:Referencing:

Georeferencing involves a series of transformations that progressively flatten the irregular surface of the Earth so measurements on an irregular spheroid surface can be represented on a flat surface.


Geoid –ellipsoid Datum

graticule

Mathematicalrepresentation

Mathematical/empiricaldefinition

Map projection

Geographic Information Systems (GIS) in Planning and ...

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