Cartographic Standards and Thematic Map Design

Posted on Nov 14, 2024 in Mathematics

Cartographic Standards for Series Mapping

These standards ensure uniformity across all pages of a series map. They specify the design of symbols, colors, and typography for a consistent result.

Lettering

Text size and spacing should reflect importance and extent. Lettering must be appropriate for its type (e.g., road, city, region) and consider order and qualitative differences.

Labeling Order

  1. Inflexible phenomena
  2. Point phenomena
  3. Linear features
  4. Surface features
  5. Contour lines

Basemap

The basemap (including projection type and item conditions) provides spatial referencing. It offers the necessary information to convey the message, a synthetic image of the area, and an important scale.

Thematic Map

This map highlights specific features. It uses the basemap as support and develops particular aspects.

Class Intervals

Types of class intervals:

  • Equal Intervals:
    • Rank (amplitude divided by the number of data points for rectangular distribution, isolines)
    • Normal distribution (useful for 2n intervals)
    • Quantiles (equally divided observed data occupy similar parts, quartiles)
  • Intervals in Progression:
    • Arithmetic (a + x + 2x + 3x)
    • Geometric (a + x + x2 + x3)
  • Irregular Intervals:
    • Breaking points (significant points of the distribution)
    • Limited exogenous (observed data values external to the subject matter, representing a natural limit, e.g., poverty)

Types of Thematic Maps

  • Qualitative Thematic Maps: Depict classified data groups measured nominally, without order or quantity relations. Surface data uses distinct colors, varying tone for qualitative differences. Black and white maps use frames with equal amounts of black and white. Repetitive frames are also used.
  • Quantitative Thematic Maps: Represent numerical spatial data with absolute or relative order and quantity. Examples include dot maps, proportional symbol maps, isoline maps, choropleth maps, cartograms, and flow maps.

Proportional Symbol Map (Absolute)

Uses linear or volumetric symbols. Symbol size reflects the value and area occupied. Perception is nonlinear. Linear surface-edge range is wider. Perception problems exist (volumes and areas are underestimated).

Dot Map

Quantitative information is represented by dots. Dot size (large covers more area, small less), value (high unit value, few points, insufficient; low unit value, mass of points), and scale are important. Size and value are analyzed in combination. Maps are easy to understand but difficult to illustrate density variations effectively. Intermittent, expensive, and laborious.

Isoline Map

Represents continuous variations in magnitude. Derived from interpolation using intervals and colors. Isometric (point data from the territory), isopleths (data per unit area).

Choropleth Map (Quantitative, Discrete, Relative)

Represents quantitative data associated with discrete enumeration units. Value remains constant within each unit. Data displayed in relative terms, classified into intervals, with darker colors for higher amounts. Corograms (enumeration units, smaller size, more detail).

Dasymmetric Map

Shows spatial variation, indicating change direction and speed. Choropleth map areas are divided to provide more detailed information. Achieves a more realistic representation.

Differences: Dasymmetric, Choropleth, and Isoline Maps

Specific data in cities use choropleth maps. For geographic organization of magnitudes, use isolines. Dasymmetric maps are used for more detailed representation. In choropleth maps, data limits coincide with the corogram. In dasymmetric maps, data limits do not coincide. In isoline maps, lines have a constant numeric value, while in choropleth and dasymmetric maps, they do not.

Flow Map (Width Proportional to Value)

Represents linear movements, such as transportation. Uses linear symbols (radial and network distribution). Target screening is important.

Cartograms (Quantitative, Continuous, Measured)

Quantitative data associated with enumeration units, resizing areas proportionally. Advantages and disadvantages (powerful representation, aids communication, but difficult to read, appears incomplete, and has low precision).

Map Generalization

Reduces complexity and the number of elements. Steps: remove (unimportant and confusing elements), simplify, and emphasize (important elements). The cartographic image strives for readability and expressiveness. Positioning maintains relative and absolute ranges. Influencing factors: scale (90% of cases), map objective (public, private), graphic limitations (production, reproduction, paper type), and information quality. Examples: maintaining proportion, maintaining joint geometry, emphasizing principal characteristics, and incorporating small forms.

Relief Representation

Structural lines are crucial. Normal lines use a metric system of representation. Contours: normal (thin, master, intermediate), bathymetric (f, m, i), depression (f, m, i), and bathymetric depression (f, m, i). Factors for choosing equidistance: scale, terrain type (maximum or minimum slope), map purpose, and production means (line thickness). Interpolated curves do not provide information. Interpolated curves provide information, unnecessary if it agrees with interpolation, excessive equidistance, local character, not without intermediate points.

Shading

Useful for understanding the terrain. Atmospheric perspective or air: based on real landscape vision, natural shades evoke a three-dimensional effect. High contrast in high areas, low contrast in low areas.

Hypsometric Tints

Represents terrain heights with different colors by altitude. Height intervals are selected with their rank and color.

Digital Terrain Models (DTM)

Simplified representation of reality. A DTM is a numeric representation of topographic characteristics expressed by XYZ coordinates.

Triangulated Irregular Networks (TIN) (Vector)

A network of irregular triangles whose vertices are the original terrain points. Delaunay triangulation can be introduced. Break lines are retained within the triangles. Thiessen polygons are generated from the union of side bisectors of neighboring triangles.

Regular Grid Models (Raster)

A grid superimposed on the ground, extracting the average height of each cell. Origin, data definitions, and row by column vector. No breaklines, small scale, large terrain data, simple structure.

TIN vs. DEM

No difference in smooth terrain. TIN is more effective with structured lines.

Douglas-Peucker Algorithm

Deletes points from linear entities. Simplifies by increasing the threshold.

Question

Representation techniques: surface (proportional symbols, absolute data), percentages (relative data, choropleth), time (varying color, proportional symbol). Equi-area projection (proportional areas).