GeoJSON serialiser that doesn't explode your nested coordinate arrays

GeoJSON Transforms

This example demonstrates how GeoJSON geometry types can be transformed into simplified or filtered representations by applying custom point, line, and polygon handlers. It builds on the D3 geo module’s type dispatch system, explicitly defining default handlers for Feature, FeatureCollection, and GeometryCollection objects alongside primitive geometries. The code uses d3_geo_type and d3_noop to create a reusable translator, showing how to override or extend processing for each GeoJSON type. The rendering approach is not shown, focusing solely on the data-transformation pipeline.

62% match

Simplify GeoJSON using d3-plugins/simplify (thanks @jasondavies for preserving topology!)

This example demonstrates how to simplify complex GeoJSON geometry while preserving topological relationships, using the `d3.simplify` API from the d3-plugins/simplify package. It shows a command-line conversion workflow that reads a GeoJSON input file, applies a simplification algorithm with zero area tolerance and topology-aware processing, and writes the simplified output to a new file. The implementation uses Node.js file I/O with `fs`, JSON parsing, and a custom projection function that passes coordinates through unchanged, making it a practical tool for reducing map data size without breaking shared boundaries.

RRandomEtc

62% match

Clean Up for Natural Earth GeoJSON

This example presents a command-line Node.js script for cleaning Natural Earth GeoJSON data. It reads a GeoJSON collection from standard input and outputs a simplified version, retaining only the `name` property and an `id` derived from either the `ISO_A3` or `FIPS` code. The script uses `JSON.parse` and `JSON.stringify` for data processing, and it rounds all coordinate values to six decimal places via a custom `round` function applied to `Polygon`, `MultiPolygon`, and `LineString` geometries. The process logs warnings for invalid country codes.

60% match

GeoJSON Contours Test

This example tests the rendering of contour lines stored as GeoJSON MultiPolygon features, with each feature carrying a numeric value property. The visualization displays these contours as filled regions across a geographic area, creating a layered map that resembles a topographic or density surface. The code uses D3’s `geoPath` to project and draw the GeoJSON geometry onto an SVG canvas, with the contour values determining the visual appearance of each region. The data comes from a gist by curran, showcasing how pre-generated contour polygons can be directly translated into a map visualization.

CCurran Kelleher

Custom Cartesian Projection

This example displays a set of land parcel polygons from a GeoJSON file, drawn as light gray shapes with black outlines on an SVG canvas. It creates a custom Cartesian projection by implementing a `d3.geoTransform` that maps raw coordinates through two `d3.scaleLinear` scales for the x and y axes. The resulting transform feeds into a `d3.geoPath` generator, which renders the geographic features using the projected coordinates, bypassing standard geographic projections.

Simplifying and cleaning Shapefiles.

This example demonstrates how to simplify and clean geographic data by rounding coordinates within a TopoJSON file. It uses D3’s `d3.round` function to reduce each point’s precision to two decimal places, then outputs the cleaned result as a JSON string. The code maps over the nested structure of polygons, line strings, and points, applying the rounding operation at each coordinate level. The visualization gallery shows the transformed data as plain text, highlighting the coordinate simplification process. The source is a GeoJSON-derived TopoJSON file, processed entirely in the browser with D3 v3.

Gist 8393714

This visualization displays a set of GeoJSON polygon features—irregular, detailed land-boundary shapes—plotted as an interactive geographic map. The polygon coordinates, which trace long, meandering outlines around the 50.6°N latitude band, are rendered as a filled region, likely using a mapping library to project the coordinates. The example appears to focus on showing raw GeoJSON geometry on a map, with the single polygon standing out against the base map, and could serve as a template for viewing or testing geographic data.

Aadkatrit