Geographic Context

Everything happens somewhere

Knowing where things happen can

help us understand why things

happen.

Location and Health

There is a close link between geography and

health.

Question

What are some ways that people‟s health can be

affected by geography?

Geography can affect health through landscape,

location of services, location of population in

need, human interaction with landscape

Medical geography

A branch of geography that looks at the relation

between location and people‟s health

Concepts are useful beyond medical geography

Long history of use of geography to understand

health and disease patterns.

John Snow cholera map

1854 London

Used map to

illustrate cholera

outbreak was

centered around a

pump on Broad St

Locking pump led to

decrease in disease

Malaria in India

Maps

Valuable tool for displaying data and helping

people understand data and direct action

Picture of a place which can give you a better

understanding

When well-made, a map can give both content

and context

Important Properties of Maps

When creating maps there are four factors that are important

Scale

Legend

Title

Source

All affect the context of data displayed and how the data is and can be INTERPRETED

Scale of a Map

What is scale?

It is the „representative fraction‟ and states the

relationship between the distance on the map (such

as one centimeter) and the distance on the ground

(such as one kilometer)

Why is scale so IMPORTANT?

The scale affects the level of detail a map shows

Large-scale maps cover small areas, but can

include a higher level of detail than small-scale

maps which depict larger areas at lower detail.

There are no precise definitions of large- or small-scale, but for

most map users, the following general scale categories apply:

• Large-scale: 1:250 to 1:1,000

• Medium-scale: 1:1,000 to 1:10,000

• Small-scale: 1:10,000 to 1:100,000

• Very Small-scale: 1: 100,000 to above

Map Scale

Source: ICIMOD, 2000

Small ScaleLarge Scale

1:500,0001:50,000

Scale

What are the general rules with scale?

Do not zoom below the scale as stated for the dataset (that is

scale at which the data was collected)

Only integrate GIS datasets that have been collected at the

same or at a similar scale

The maximum scale a dataset should be viewed is

approximately 100 times the Scale that is stated in the Metadata.

For Example: Data collected at 1:5,000 should not be viewed

above 1:500,000

Title

Scale

Bar

North

Arrow

Legend

Data

Source

TYPES OF MAP

Graduated Circle Map

Size of symbol corresponds to data.

Advantages:

•Easily see extreme ends of the

data distribution

•Geographic patterns emerge

Disadvantages

•Can be challenging to differentiate

the middle of the distribution since

the eye can‟t easily detect small

differences in size

Concentration of Vulnerable Population-Meerut City(Using 2 Km Radius)

POPULATION DISTRIBUTION

Population distribution is critical in health planning

Map credit UHRC

Choropleth

Polygons are shaded to match data

distribution

Advantages:

•Easy to see geographic distribution

•Easy for most people to interpret

Disadvantages

•Polygons can hide uneven

distributions within boundaries

•If patterns/colors aren‟t chosen

wisely the map can be difficult to

interpret

Continuous surface

maps

Data is distributed continuously

across space

Advantages:

• Very easy to see hot spots or

areas that deviate from other

areas

Disadvantages

• Not all data can be distributed

continuously

Depiction of Malaria incidences in Trans Yamuna Region (Allahabad District)

Village-wise Slide Positivity Rate (Malaria) of Trans-Yamuna Region

2002 2004

Low High

Depiction of Malaria incidences in Trans Yamuna Region (Allahabad District)

Village-wise Slide Positivity Rate (Malaria) of Trans-Yamuna Region

2002 2004

Low High

Depiction of Malaria incidences in Trans Yamuna Region (Allahabad District)

Village-wise Slide Positivity Rate (Malaria) of Trans-Yamuna Region

2002 2004

Low High

Other types

With advanced software it‟s

possible to produce diagram maps

that display data using charts.

Advantages

•Effectively displays complex

information

•Lots of information on each map

Disadvantages

•Can have too much information

•Can be difficult to structure data to

produce such maps

•Requires an advanced GIS

Which map style should you use?

Depends on type of data you have

What purpose you want the map to serve

Sometimes a matter of experimentation to find

the map style that best fits the data and purpose

of the map

It‟s important to pick the type of map that makes the

data most useful

Basic cartographic concepts

Map Design

Cartographic standards

Generalization

Graphic Variables

Use of Color

Classification of Data

Methods of Mapping

Map making is both science and art.

Maps influence people‟s perception of space. This

influence is partly because of convention and partly

because of the graphics used.

People understand the world differently, express this

understanding differently in maps, and gain different

understanding from the maps.

Map Design

Cartographic standards

There are cartographic standards that have emerged that

make it easier to interpret and read maps.

These standards do not have to be followed, but if they aren‟t

your map may be less readable.

Administrative

Boundaries

--Most often black or

gray.

--The higher the

administrative unit

the thicker the line

Roads

Color and line styles to

represent road type with

major roads being

thicker or more

distinctively colored than

minor roads.

Rivers and Lakes

--Blue

--Streams dashed,

lines light blue

Map Design

Generalization

Maps contain a

certain level of detail

depending upon the

scale and purpose.

Sometimes the map

maker will need to

simplify features to

make them more

readable.

Use of Color

Color perception has psychological, physiological and

conventional aspects.

It has been noted that it is difficult to perceive color in small areas,

and more contrast is perceived between some colors than

between others.

In addition to distinguishing nominal categories, color differences

are also used to show deviations or gradation.

Hue

Saturation

Intensity

Source: ICIMOD 2000

Use of Color

Color blindness

5-8% of men

0.5% of women

Black-and-white

Consider

method of

reproduction

or output of

maps

Making an effective map is a

matter of finding the right balance

between the limitations of the

data, the needs of the map reader

and the message you, as the map

maker, want to convey.

Issues to Remember

Maps can LIE!!

Maps are just one person‟s representation of the

“real world”

Like any source of information they can be

misleading especially when used out of context

How maps can be deceiving

Inappropriate Legend

Inappropriate Scale

Inappropriate Data Classification

Source: ICIMOD, 2000

Key points

Everything happens somewhere

Geography is a common denominator across

human activity

There are different types of maps. Picking the

right style means balancing the needs of the

reader, the data and the message you as

mapmaker want to convey.

Key points

The mapmaker can use colors, symbology, and

generalization techniques to make maps

readable to the audience.

Any questions?