The style guide

The sheet above is not a drawing of the style but a product of it: ulg sheet renders it from the same data that styles your maps, so the guide and the maps cannot drift apart. The German version is img/style-sheet-de.png.

2.1 Five principles#

The UrbanSens reference sheet names five design principles. The library turns each of them into something that can be checked:

Vector-based (polygonizable, GIS compatible) · Subtle, natural color palette · Consistent iconography and line weights · Minimal, non-photorealistic, architectural style · Scalable detail (works at all zoom levels)

UrbanSens, reference sheet of the Ecological Vector Style, "Design principles"

2.2 Colour#

The palette has 21 families of primitive colours, addressed as family.step. Elements, themes and exporters refer to tokens only; changing a token changes every map, sheet and export at once.

Rules

• Areas use the light steps (100–400); texture marks use darker steps of the same family (600–900), so a texture always reads as part of its surface.
• Outlines are the fill darkened by a fixed amount (settings.json → outline_darken), unless an element sets its own.
• Saturated colour is reserved for meaning: the signal family marks what is planned, removed, protected or highlighted. Never use it for land cover.
• Neighbouring land covers must differ by at least ΔE₀₀ 10 in colour, or else in texture or outline (checked by ulg check, see 2.8).

For analysis layers there are ready ramps and class palettes in the same tonal range:

ulg.ramp("heat", 5)                  # ['#F7F1DC', '#F6D5A5', '#EFAC77', '#DB805F', '#B5574F']
ulg.category_of("utci", 34.2)        # {'id': 'strong_heat', 'min': 32, 'max': 38, 'color': '#F0B273', ...}

2.3 Textures#

Seventeen texture motifs draw every surface. Each element picks one or two motifs and their inks from the palette:

How textures behave

• Anchored to the ground. Mark positions are derived from ground coordinates, not from the feature. Two neighbouring polygons of the same element continue each other's pattern, and a map panned or tiled shows the same marks in the same places.
• Seamless tiles. For QGIS, SLD and the web the same motifs are drawn into periodic tiles that repeat without seams.
• Clipped to their area. Crowns and marks never spill over the feature edge, so drawing order never changes the look of clean data.
• Density by level of detail (2.6), not by feature size, so a texture looks the same on a small and a large polygon.

2.4 Lines#

Line elements use the ISO 128 series from settings.json → line_weights: hair 0.13, fine 0.18, regular 0.25, medium 0.35, bold 0.5, heavy 0.7, extra 1.0 mm. Texture marks are drawn finer than the finest outline on purpose: they must never compete with a boundary.

Lines and roads or paths that arrive as centre lines (OpenStreetMap highways) are drawn above all land cover. Area elements such as roads and footways become strips of their real width (see 2.7).

2.5 Symbols#

Trees are drawn to scale. A crown is a lobed outline of the tree's real diameter (attribute crown_diameter, or the element default), with a branch star from 1:1 500 upwards. When a stem diameter or girth (stammumfang in cm) is known, the stem is drawn to scale too.

Status follows the standards. One grammar serves all planning drawings:

The root protection zone (ulg.root_protection_zone()) is the crown drip line plus 1.50 m (columnar trees plus 5.00 m) after DIN 18920; the minimum distance for trenches is four times the stem girth, at least 2.50 m.

Pictograms mark furniture and ecological structures (bench, bin, lamp, bicycle stand, sign, play equipment, planter, bollard, deadwood, stone pile, nesting aid …). They are drawn at a fixed paper size, so they stay legible at every scale, and enlarged automatically in legends and sheets.

2.6 Levels of detail#

ulg.lod_for_scale(500) → 3, ulg.lod_for_zoom(18) → 2. Give the scale; do not switch textures off by hand.

2.7 Drawing order#

Real data is often stacked: OpenStreetMap maps a park as one polygon and the lawn, the pond and the paths inside it as further polygons on top. The style draws in bands so that stacked data looks right and clean data is unaffected:

Inside the ground band smaller areas are drawn on top of larger ones, the rule OpenStreetMap Carto uses for land cover. A playground inside a park, a lawn covering the park, a meadow inside the lawn and a clearing inside a wood all stay visible, and a complex such as a park never hides the surfaces mapped inside it. Water comes above the ground band because ponds are routinely mapped on top of parks and woods. ulg.flatten() applies the same order to the geometry itself, which turns stacked data into a clean partition for area statistics.

2.8 Legibility#

ulg check (and the test suite) enforces three rules:

1. Distinguishable. Two land covers that are closer than ΔE₀₀ 10 must differ in texture or outline. Pairs that differ in nothing are errors.
2. Colour-vision safe. The same test is repeated after simulating protanopia, deuteranopia and tritanopia (Machado et al. 2009). Meaning never depends on hue alone (WCAG 2 success criterion 1.4.1).
3. Marks with contrast. Texture marks are measured against their fill; the report lists the weakest, and symbols and boundaries follow WCAG 1.4.11 for non-text contrast.

2.9 Typography and layout#

Sheets, legends and titles use a humanist sans-serif (Avenir Next, falling back to Nunito Sans, Source Sans 3, Helvetica Neue, Arial), ink.900 for titles and ink.500 for secondary text, small capitals with wide tracking for section heads, and thin ink.200 rules. Maps are laid out in paper millimetres at the chosen scale.

2.10 Themes: the same map in other conventions#

The house style is mellow. Six further themes redraw the same data in an official or familiar convention, with the colour values of the published source: planzv (land-use and zoning plans), alkis (cadastral map), basemap (basemap.de), bfn (landscape planning), osm (OpenStreetMap Carto) and mono (black-and-white drawing after ISO 11091). Official themes use flat colours and exact lines. Sources and evidence: Standards and reference/themes.md.

2.11 Do and don't#

2.12 The mark#

The logo spells ulg with three things of a landscape plan, each drawn by the library from a catalog element: a pond in the shape of a u (water), a tree-lined path as the l (waterbound and tree), and a tree crown with a stream as the tail of the g (tree and watercourse). The hand-drawn outline and the texture marks are the renderer's, so the mark is a specimen of the style: exact geometry underneath, an imperfect drawing on top.

The name is set in Rethink Sans (SIL Open Font License) and converted to outlines, so the files need no font. Keep a free margin of half the height of the mark around it, show it at no less than 24 px tall (use ulg-mark-small.svg below 40 px), and do not recolour it: the colours are palette tokens (water.300, sand.300, leaf.300–leaf.600). python tools/build_logo.py redraws every file from the catalog, so a change of the palette changes the logo with it.

The UrbanSens mark. The style sheet, the catalog sheets and the figures of this documentation carry the small UrbanSens logo in a corner, with the website and the version; credit=False leaves it out. Details and the credit request: Licence and credit.