GIS Maps

The same building heights data can be unreadable or immediately clear depending on how you style it. This module covers the three main styling approaches: single symbol, graduated (for continuous numeric data), and categorised (for categorical data).

Create a new project (Project → New) and add the Neighbourhoods, Blocks, Buildings, and Premises GeoPackages from the datasets page.

Tip

This exercise requires the Layer Styling panel. If not visible, go to View → Panels → Layer Styling. This opens a docked panel for styling the selected layer. Alternatively, double-click any layer and select Symbology, but this opens a separate dialog you’ll need to reopen for each layer.

Warning

Save your project regularly (Ctrl+S / Cmd+S). Frequent saves prevent lost work.

Neighbourhoods

  • Notice the ordering of the layers in your Layers panel. Select the individual layers and drag to reorganise them so that the smallest (premises) is at the top, then buildings, then blocks, then neighbourhoods.
  • Hide all layers except neighbourhoods by unchecking their visibility boxes in the Layers panel. Double-check that the neighbourhood layer is selected.
  • Then, in the Layer Styling panel, select the Symbology tab, then choose a default style or create your own by selecting Single Symbol and setting the fill colour, opacity, stroke width, and stroke colour.
  • Use the Identify Features tool to select a neighbourhood. Inspect the available fields. Notice that the NOMBRE field contains the neighbourhood name.
  • Go back to the Layer Styling panel, select the Labels tab, then select Single Labels, then select the NOMBRE field. Set the font, size, style, and be sure to pick a colour of sufficient contrast. Notice that the neighbourhood names are now displayed.
  • Take some time to explore some of the more advanced text styling options such as buffers, masks, placement, and rendering options

Blocks

  • Activate visibility for the blocks layer.
  • Inspect (Identify Features tool) one of the blocks to see available data fields. If you see information for a different layer, check that the correct layer is currently selected in the Layers panel, and that the Identify Results panel Mode is set to Current Layer. Notice the block_orientation field, which represents the predominant orientation angle of each block.
  • Go to the Layer Styling panel and select the Symbology tab. The data field is continuous numeric data, so select the Graduated display option, then select block_orientation for the Value.
  • For Color Ramp, select Random Color Ramp. For orientation data, random colours work because there’s no inherent “high” or “low” value: 0° and 45° aren’t better or worse than each other, they’re just different directions.
  • Below the Classes panel, select Fixed Interval for the Mode and set the interval to around 5-10 degrees. This creates colour bands at fixed intervals, making it easy to see which blocks share similar orientations.

Blocks Style

Buildings

  • Activate visibility for the buildings layer. This time, we’ll visualise the mean_height field.
  • In the Layer Styling panel, select Symbology. Building heights are continuously distributed numeric data, so use the Graduated display option and select mean_height for the Value field.
  • For Color Ramp, select a sequential scheme like Rocket or YlOrRd. Unlike orientation, height has meaningful “low” and “high” values, so a sequential colour ramp (light to dark, or cool to warm) communicates that relationship.
  • Select Equal Count for the mode and increase the number of Classes to around 10-20.
  • Expand the Histogram section at the bottom of the Symbology tab and click Load Values. This shows you the distribution of building heights and where the classification breaks fall. Most buildings are low-rise, with a long tail of taller buildings.
  • Experiment with different Mode options:
    • Equal Interval spreads thresholds evenly, but doesn’t work well here because the outliers (few very tall buildings) mean most of the colour range is wasted on heights that rarely occur.
    • Equal Count puts the same number of features in each class, which uses the full colour range but can obscure the actual distribution.
    • Logarithmic Scale handles long-tailed distributions well by compressing the high end, but can be unstable when the data contains zeros.
    • Natural Breaks (Jenks) finds natural groupings in the data. It can be slow on large datasets but often produces intuitive results.

Buildings Style

Premises

  • Activate visibility for the premises layer. Here, we’re interested in the land uses contained in the section_desc field.
  • Select the premises layer, then go to the Layer Styling panel and select the Symbology tab. This time, select Categorized because section_desc contains discrete categories rather than continuous numbers.
  • Select section_desc for the Value field, then click Classify to populate the category list. Click on the Symbol button to fine-tune the colour, size, opacity, and stroke settings.

Premises Style

Assignment: Map data from your data catalogue

NoteChallenge

Using datasets from your data catalogue, create 2-3 maps that showcase different data types or themes from one of the pilot cities.

Consider: What story does this data tell? What patterns or relationships become visible when mapped?

Focus on clarity. Someone unfamiliar with the data should understand the key patterns at a glance.

NoteReading

Module: Laying out the Maps