Principles of gis by Gokhale Lecture12_BGTD.ppt

GIS

1. GEOL 403/503 GEOL 403/503
Principles of GISPrinciples of GIS
Bhushan GokhaleBhushan Gokhale
Ted DunsfordTed Dunsford
Fall 2007Fall 2007

2. Lecture 8Lecture 8
Cartography: Symbology, Cartography: Symbology,
Labeling, and ClassificationLabeling, and Classification

3. Why we need Cartography?
 Time, effort and cost savings
 Increase common understanding
 Sharable symbology and guidance
among different agencies

4. Concept of Cartography?
Common map appearance
Common interactive map experience
across different agencies

5. Characteristics of
Cartography
Scale Dependencies
Symbology and Labeling
(Type, Color, Size, Fill, Transparency,
etc.)
Layer Display Order
Extents

6. How can you have good
Cartographic practices?
What layers?
FGDC and National Map framework standards
What symbology?
Use existing cartographic standards when they
are available
USGS National Mapping Program
Publication Symbols
What are other people using?
What looks reasonably good?

7. Symbology BasicsSymbology Basics

Maps - hardcopy or digital symbolic Maps - hardcopy or digital symbolic
representations of geographic phenomenarepresentations of geographic phenomena
Geographic phenomena include location, Geographic phenomena include location,
distance, volume, movement, function, process, distance, volume, movement, function, process,
correlation, etc. correlation, etc.

Four types of geographic phenomenaFour types of geographic phenomena
PointPoint (non-dimensional data) (non-dimensional data)

LineLine (one-dimensional data) (one-dimensional data)

AreaArea (two-dimensional data) (two-dimensional data)

VolumeVolume (three-dimensional data) (three-dimensional data)

8. Typical SymbologyTypical Symbology

9. Symbol DesignSymbol Design

Select the geographical features you want on the Select the geographical features you want on the
map map

Define scale of the map so that the intended features Define scale of the map so that the intended features
are visible and legibleare visible and legible

Avoid congestion and sparsityAvoid congestion and sparsity

Two types of symbol designTwo types of symbol design

Pictorial map symbolsPictorial map symbols

Abstract map symbolsAbstract map symbols

10. Symbol Design in Different Symbol Design in Different
EnvironmentsEnvironments

General ConsiderationsGeneral Considerations

Screen resolution - for digitalScreen resolution - for digital

Map scaleMap scale

ColorColor

Size Size

The level of detailThe level of detail

Features you want to representFeatures you want to represent

Intended audienceIntended audience

11. Data ClassificationData Classification

When a data set is large, it is not practical to When a data set is large, it is not practical to
assign a unique symbol to each data recordassign a unique symbol to each data record

Therefore, it is essential to group the recordsTherefore, it is essential to group the records

Several methods of classifying data in ArcGISSeveral methods of classifying data in ArcGIS

Check for Check for

Qualitative dataQualitative data

Quantitative dataQuantitative data

Nominal dataNominal data

Ordinal dataOrdinal data

12. Constructing Data ClassificationConstructing Data Classification
Statistical methods for the classification or Statistical methods for the classification or
ranging of interval/ratio data ranging of interval/ratio data
Classification could be based onClassification could be based on

Equal intervalEqual interval
Defined intervalDefined interval

QuantileQuantile

Standard deviationStandard deviation

Natural breaks (Jenks)Natural breaks (Jenks)

13. Data SymbolizationData Symbolization

Nominal data Nominal data
symbolsymbol

Ordinal data Ordinal data
symbolsymbol

Interval and ratio Interval and ratio
data symboldata symbol

Color palettesColor palettes

14. Labeling a MapLabeling a Map

Look for neatness of the mapLook for neatness of the map

Some features need a labeling but some don’tSome features need a labeling but some don’t

Use proper font size and color for clarity in reading Use proper font size and color for clarity in reading
labelslabels

In a particular feature look for which attribute is a In a particular feature look for which attribute is a
good representation of the feature and should be good representation of the feature and should be
used for labelingused for labeling

Do not use repeated labelingDo not use repeated labeling

In some cases, halo effect is required to bring In some cases, halo effect is required to bring
prominence to your labelprominence to your label

In many cases, scale rendering function need to In many cases, scale rendering function need to
used to show labeling at a particular scale while used to show labeling at a particular scale while
zoomingzooming

15. Base ElementsBase Elements

Internal Internal

ExternalExternal

16. Internal Base ElementsInternal Base Elements

Geographic featuresGeographic features

Physical and culturalPhysical and cultural

landmarks, boundaries, roads, rivers, topography.landmarks, boundaries, roads, rivers, topography.

Textual labelsTextual labels

words and numbers identifying or describing words and numbers identifying or describing
features.features.

17. External Base ElementsExternal Base Elements

TitlesTitles

North ArrowNorth Arrow

LegendLegend

Scale bar and representative fractionScale bar and representative fraction

Source and creditsSource and credits

InsetsInsets

etc.etc.

18. Designing a mapDesigning a map

Include the base elements.Include the base elements.

Customized for the audience.Customized for the audience.

Focus on the messageFocus on the message

19. What is emphasized???What is emphasized???

20. GeneralizationsGeneralizations

Every map contains errorsEvery map contains errors

Primary source of error in cartography is Primary source of error in cartography is
GeneralizationGeneralization

21. GeneralizationsGeneralizations

22. ScaleScale

Large-scale = relatively smaller numbers Large-scale = relatively smaller numbers
(1:10,000), more detail, and less area (1:10,000), more detail, and less area
(smaller geographic extent).(smaller geographic extent).

Small-scale = relatively larger numbers Small-scale = relatively larger numbers
(1:250,000), less detail, and more area (1:250,000), less detail, and more area
(larger geographic extent).(larger geographic extent).

These comparisons are relative.These comparisons are relative.

23. ResolutionResolution

Absolute resolutionAbsolute resolution

Relative resolutionRelative resolution

24. AccuracyAccuracy

Absolute accuracyAbsolute accuracy

Relative accuracyRelative accuracy

25. PrecisionPrecision

Measure of repeatabilityMeasure of repeatability
Accuracy Accuracy
versus versus
PrecisionPrecision

26. MMUMMU

Minimum Mapping UnitMinimum Mapping Unit

27. DEMODEMO