Lesson 2 Geographic Context and Map Fundamentals

MEASURE EvaluationPHFI Training of Trainers

May 2011

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

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 and the distance on the ground

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 dataset 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 MapSize 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

ChoroplethPolygons are shaded to match data distributionAdvantages:• 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 mapsData is distributed continuously across spaceAdvantages:• Very easy to see hot spots or

areas that deviate from other areas

Disadvantages• Not all data can be distributed

continuously

Other typesWith 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 standardsThere 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 BoundariesMost often black or gray.

The higher the administrative unit the thicker the line

RoadsColor and line styles to represent road type with major roads being thicker or more distinctively colored than minor roads.

Rivers and LakesBlueStreams dashed lines light blue

Map Design

Generalization Maps contain a

certain level of detail depending upon its 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

Classification of Data The representation of data for mapping will depend on the measurement scale of the data.  

Nominal scale: The differences in data are only of qualitative nature, e.g., differences in facility type, land use or geology. 

Interval scale: Both the hierarchy and the exact distance is known, but it will not be possible to know the ratios, e.g., the temperature or the altitude values. Ratio scale: Data can be measured on a ratio measurement scale, e.g., the number of children in a family or income. 

Ordinal scale: Only the order of the attribute values is known, such as more than or less than, “small - medium – large” or “cool - tepid - hot”.  

Source: ICIMOD 2000

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

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 is 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 among other techniques to make maps readable to the audience.

Any questions?