Developing on d3-geo-projection for d3 v4

projection debugging

This example visually compares two map projections of the same world dataset by layering them in red and blue on a canvas. Using D3’s `geoTransform` and `geoProjection`, a standard equirectangular projection (blue) is juxtaposed with a custom sheared transform (red) that skews longitude by latitude. The code loads world country boundaries from a local JSON file and renders both outlines overlaid, making differences in shape, rotation, and distortion immediately visible. The canvas drawing highlights how tiny variations in projection logic can produce significant spatial divergence, offering a quick, intuitive way to debug or inspect map projections.

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visualizing map distortion d3v4

A side-by-side visualization demonstrates map projection distortion by pairing an interactive Aitoff projection with a fixed orthographic globe. The user can pan and zoom the left map via `d3.zoom`, while the right globe rotates to match the map’s center using `projection.invert` and `projection.rotate`. A grid of red dots, generated as screen coordinates, is overlaid on both views; on the map they appear directly, while on the globe their positions are computed through the inverse projection, revealing how distances and shapes stretch across different projections. The implementation uses `d3.geoPath`, `d3.geoGraticule`, `d3.geoProjection`, and TopoJSON world data, with SVG rendering.

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Poor man's Composite projection

Four map projections—Lagrange, azimuthal equal-area, orthographic, and azimuthal equidistant—are arranged in a 2x2 grid to form a single composite projection. The d3.geoPath renderer draws world landmasses from TopoJSON, a graticule, and the sphere outline, with each projection clipped to its quadrant. A custom `projection.invert` method tests each quadrant to locate mouse positions, and the red inverted point follows the cursor. Continuous rotation of all four projections via d3.timer produces an animated display.

66% match

Tobler–Mercator

This example demonstrates the Tobler–Mercator projection, a modified Mercator projection that preserves area. The world map is rendered with graticule lines, country boundaries, and a white sphere outline. Built with D3 v4, it combines `d3.geoProjection` with a custom projection function and `d3.geoPath` for geographic rendering. The map uses TopoJSON data from the world-atlas package, with land and country boundary geometries loaded via `d3.json` and processed using `topojson.feature` and `topojson.mesh`. The visualization is fully SVG-based.

Mmbostock

d3v5 - Selective Projection Map

This example visualizes a world map with a dropdown menu to switch between over 40 different geospatial projections, including Miller, Mercator, and Robinson. The map is rendered as SVG using d3.geoPath, while the projection options are defined with d3-geo-projection methods like d3.geoMercator and d3.geoMiller. World coastlines come from a GeoJSON file, and a graticule and sphere outline are added to each view.

HHirosaji

Zoom and Rotating (Reprojecting)

This example demonstrates map reprojection with zoom and rotation using D3 v4 and canvas rendering. It displays geographic data from `ne_110m_admin_0_sovereignty.geojson` and a graticule, drawn with `d3.geoPath` and a `d3.geoEquirectangular` projection that rotates over time via `d3.timer`. The scene is embedded in an A-Frame 0.5.0 environment with multiple canvas textures applied to 3D entities, including a sphere and plane, using the `draw-canvas` component.

AAlexanderDavidson

Tetrahedric Gnomonic Projection

This example visualizes the world using a tetrahedric gnomonic projection, a polyhedral map projection that unfolds the globe onto four triangular faces. The map renders landmasses and graticules on a Canvas via `d3.geoPath`, with the projection implemented through a custom `d3.geoTetrahedralLee` function that uses `d3.geoPolyhedral` and per-face gnomonic projections. The code includes a dashed inner triangle and outlined sphere boundary, and loads world data from the World Atlas TopoJSON dataset. It also spins the projection interactively using D3's rotation APIs and renders at devicePixelRatio for sharp output.

Projection Transitions

A drop-down menu and an auto-advancing timer cycle through dozens of map projections, each rendered over a world map with a graticule and sphere outline. The example shows how D3’s `d3.geo.path` and the `d3.geo.projection` plugin smoothly interpolate between projections using the `transition` API, with land from TopoJSON. A menu allows manual selection, while a periodic random selection demonstrates animated morphing between projections.

Mmbostock