Styling and Labelling Layers

Lesson 4 of 8 · GIS Software Fundamentals · Beginner

Styling controls how your data looks on the map. Good styling makes a map readable and meaningful. Poor styling can obscure patterns, mislead viewers, or make a map impossible to interpret.

What Styling Does

Styling changes the visual appearance of a layer — colours, symbols, line widths, fill patterns, transparency, and labels. It does not change the underlying data. A park styled in red is still a park; the source data is unchanged.

Layer Order

Layers are drawn in order from bottom to top in the layers panel. Polygon layers (such as neighbourhood boundaries) should generally sit below point and line layers so they do not cover features you need to see. Adjust layer order by dragging layers in the panel.

Symbol Types

• Single symbol — all features in the layer use the same symbol. Useful when the category is uniform (all parks, all roads of one type).
• Categorized — features are styled by a text or category field. Each unique value gets a distinct colour or symbol. Useful for land-use types, facility categories, or road classifications.
• Graduated — features are styled by a numeric field, grouped into class intervals. Useful for population counts, area sizes, or other quantities.

Choosing the wrong symbol type for your data type is a common mistake. Graduated styling applied to a category field produces misleading results.

Classification and Class Intervals

When using graduated styling, you must choose how to divide your data into classes. Common methods include equal intervals, quantiles, and natural breaks. Each method produces a different visual result and can tell a different story. Review the distribution of your data before choosing a classification method.

Too many classes reduce readability. Five to seven classes is a common practical limit for choropleth maps.

Labels

Labels display text from an attribute field on the map. Common choices include feature names, identifiers, or values. Label settings control font, size, colour, placement, and whether labels appear at all zoom levels or only at certain scales.

Overlapping labels reduce readability. Most GIS software has automatic label placement options that reduce overlap, but manual adjustment is sometimes needed for important features.

Accessibility and Colour

Colour choices affect who can read your map. Consider:

• Sufficient contrast between features and background.
• Colour-blind accessibility — avoid red-green combinations as the sole distinguishing factor.
• Sequential colour schemes for ordered data (light to dark).
• Diverging colour schemes for data with a meaningful midpoint.
• Qualitative colour schemes for unordered categories.

Default styling in GIS software is not designed for accessibility or communication — it is a starting point only.

Practical Example

You have a parks layer for Riverton with a field called park_type containing values such as "neighbourhood park," "sports field," and "natural area." You apply categorized styling, assigning a distinct colour to each type. You add labels from the park_name field, set to appear only at scales larger than 1:10,000 to avoid clutter at small scales.

Common Mistakes

• Using too many colours or classes, making the map hard to read.
• Applying graduated styling to a category field.
• Choosing colours that are indistinguishable for colour-blind viewers.
• Leaving default styling without reviewing whether it communicates your data clearly.
• Forgetting that styling changes are not saved to the source data — they are part of the project.

Key Takeaways

• Styling changes appearance, not source data.
• Layer order controls which features are visible on top.
• Match symbol type to data type: single symbol, categorized, or graduated.
• Choose classification methods thoughtfully for graduated styling.
• Design for colour-blind accessibility and sufficient contrast.