topojson1.5 KB

TopoJSON — Geometry Ids Alongside Properties

Five town geometries that each carry both an `id` member and a `properties` object. TopoJSON keeps these separate, and converters that fold the id into properties (or drop it) break joins against an external attribute table.

Geospatial JSON parsing Metadata testing

Preview — first 50 linestopojson

{
  "type": "Topology",
  "objects": {
    "towns": {
      "type": "GeometryCollection",
      "geometries": [
        {
          "type": "Point",
          "properties": {
            "name": "Kestrel Bay",
            "population": 4820,
            "founded": 1786
          },
          "coordinates": [
            -12.482,
            47.064
          ],
          "id": "KB"
        },
        {
          "type": "Point",
          "properties": {
            "name": "Marram",
            "population": 1180,
            "founded": 1834
          },
          "coordinates": [
            -12.3915,
            47.112
          ],
          "id": "MR"
        },
        {
          "type": "Point",
          "properties": {
            "name": "Holloway",
            "population": 2670,
            "founded": 1801
          },
          "coordinates": [
            -12.551,
            47.018
          ],
          "id": "HW"
        },
        {
          "type": "Point",
          "properties": {
            "name": "Ninepin",
            "population": 640,

… 77 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
Geometries: 5
Arcs: 0
Ids Present: true
Properties Present: true
Quantization: none

Testing contract

Expected to pass

Scenario: Convert to GeoJSON and inspect where each identifier ends up.
Expected result: Every geometry keeps its id as a Feature id — KB, MR, HW, NP, QC — rather than having it merged into or replaced by a property.

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 — Geometry Ids Alongside Properties” is a deterministic Novus Examples fixture for Geospatial, JSON parsing, Metadata testing. 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.