topojson6.7 KB

TopoJSON — Coarse 100-Step Quantization (visible rounding)

The same territory quantized to only 100 steps, so rounding error reaches roughly 220 m and several vertices collapse onto the same grid cell. Use it to prove that a tolerance in your comparison code is actually being applied rather than accidentally passing.

Geospatial Conversion testing Error handling

Preview — first 50 linestopojson

{
  "type": "Topology",
  "transform": {
    "scale": [
      0.0028282828282828396,
      0.0019191919191918962
    ],
    "translate": [
      -12.64,
      46.95
    ]
  },
  "objects": {
    "territory": {
      "type": "GeometryCollection",
      "geometries": [
        {
          "type": "Point",
          "properties": {
            "name": "Kestrel Bay",
            "code": "KB",
            "kind": "town",
            "population": 4820,
            "founded": 1786
          },
          "coordinates": [
            -12.482,
            47.064
          ]
        },
        {
          "type": "Point",
          "properties": {
            "name": "Marram",
            "code": "MR",
            "kind": "town",
            "population": 1180,
            "founded": 1834
          },
          "coordinates": [
            -12.3915,
            47.112
          ]
        },
        {
          "type": "Point",
          "properties": {
            "name": "Holloway",
            "code": "HW",
            "kind": "town",

… 439 lines total — download for the full file.

Specifications

Format: TopoJSON 1.0
Crs: WGS 84 (EPSG:4326)
Encoding: UTF-8
Line Endings: LF
Objects: 1
Arcs: 10
Quantization: 100
Transform: true
Max Position Error Metres: 220
Delta Encoded: true

Testing contract

Expected to pass

Scenario: Decode and diff against the unquantized twin with a tight tolerance, then with a 250 m tolerance.
Expected result: The tight comparison fails with errors up to roughly 220 m; the 250 m comparison passes, and collapsed vertices are visible as repeated positions.

What is a .topojson file?

TopoJSON is an extension of GeoJSON that encodes topology. Shared boundaries are stored once as arcs and referenced by the geometries that use them, coordinates are quantised to an integer grid and delta-encoded, and a transform object records the scale and translation needed to recover real positions. For data with many adjacent polygons — administrative boundaries especially — files are dramatically smaller than the equivalent GeoJSON.

How to use this file

Use an example .topojson file to test TopoJSON readers and GeoJSON converters, verifying that arcs are dereferenced in the right direction, that negative arc indices are handled, and that the quantisation transform is reversed exactly.

How to use this file for testing

“TopoJSON — Coarse 100-Step Quantization (visible rounding)” is a deterministic Novus Examples fixture for Geospatial, Conversion testing, Error handling. GeoJSON, GPX, and KML files with points, lines, polygons, and tracks — for testing map tools, route parsers, and geo importers.

Documented properties for this file: UTF-8 · LF · TopoJSON 1.0. Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.

Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.

Geospatial fixtures publish one invented territory across formats, with the coordinate reference system and feature counts documented in specs. Convert or reproject and diff against the twin in the same group; edge-case geometries state exactly which assumption they are built to break.