Lecture 3

Question 1

What is the primary difference between discrete and continuous spatial data?

A. Discrete data refers to gradually varying data, while continuous data consists of distinct points.

B. Continuous data refers to data existing in distinct locations, while discrete data varies smoothly.

C. Discrete data exists in distinct, separate locations, while continuous data varies smoothly over space.

D. Continuous data refers to abrupt variations, and discrete data refers to smooth variations.

Answer 1

C. Discrete data exists in distinct, separate locations, while continuous data varies smoothly over space.

Explanation: Discrete data consists of distinct, separate entities (e.g., cities), while continuous data changes smoothly across space (e.g., elevation).

Question 2

Which colour model is most commonly used for printing purposes?

A. RGB
B. HSV
C. CMYK
D. Munsell

Answer 2

C. CMYK

Explanation: CMYK (Cyan, Magenta, Yellow, Key/Black) is specifically designed for printing, ensuring accurate reproduction of colours.

Question 3

What visual variable is best suited for representing quantitative differences on a map?

A. Shape
B. Size
C. Colour hue
D. Texture

Answer 3

B. Size

Explanation: Changes in size are commonly used to represent quantitative differences, such as population or intensity.

Question 4

Explain the difference between mathematical and perceptual scaling when using size as a visual variable.

Answer 4

• Mathematical scaling directly relates the size of the symbol to the data value but can lead to misinterpretation because readers often underestimate large symbols.
• Perceptual scaling adjusts sizes to account for human perception, often using range grading to make symbols more visually intuitive.

Explanation: This distinction ensures effective data representation by considering both accuracy and user perception.

Question 5

Describe the advantages and limitations of using the HSV colour model in thematic mapping.

Answer 5

Advantages:
- Intuitive representation of hue, saturation, and value, making it user-friendly for certain mapping tasks.
- Useful for thematic applications requiring distinctions in saturation and brightness.
- Limitations: Inconsistent perception of lightness across different hues, leading to potential misinterpretation.

Explanation: While HSV is intuitive, its perceptual inconsistencies require careful application in cartography.

Question 6

A map shows population density using proportional circles. Symbols overlap heavily in urban areas. Suggest a strategy to address this issue.

Answer 6

Use range grading to classify population density into classes and assign non-overlapping sizes. Alternatively, employ transparency or arrange symbols hierarchically by size.

Explanation: These methods reduce visual clutter while preserving the map’s readability.

Question 7

Given rainfall data for a region, recommend a suitable colour scheme and justify your choice.

Answer 7

A sequential colour scheme is appropriate, as it uses a progression of lightness to represent rainfall intensities, with lighter colours for lower rainfall and darker colours for higher.

Explanation: Sequential schemes are ideal for continuous quantitative data, ensuring clear representation of variations.

Question 8

You are designing a geological map showing abrupt changes in rock types and their spatial extent.

• What type of data structure would you use (discrete/continuous)?
• Which visual variables would be most effective for this map?

Answer 8

• Data Structure: Discrete, as geological units are distinct entities.
• Visual Variables: Shape and colour hue for distinguishing categories, and texture for additional differentiation.

Explanation: Discrete data and appropriate visual variables ensure the map accurately conveys the categorical differences in rock types.

Question 9

Design a thematic map illustrating unemployment rates in a country.

Discuss:
- The level of measurement.
- The most appropriate visual variables and colour scheme.

Answer 9

• Level of Measurement: Ratio, as unemployment rates are quantitative with a true zero point.
• Visual Variables: Size for proportional symbols or a sequential colour scheme for choropleth maps.
• Colour Scheme: Sequential, with lighter shades for lower rates and darker shades for higher rates.

Explanation: These choices optimize clarity and accuracy, aligning visual representation with the data’s quantitative nature.