mini-gis-geo

Point-in-polygon and distance helpers for miniGis map export JSON: categories plus markers with lat / lng. No map UI—pure functions for Node or any ESM JavaScript runtime.

Designed for JSON exported from the miniGis editor (or any object with the same categories / markers shape).

Install

npm install mini-gis-geo

This package is ESM only ("type": "module"). Use import, not require.

Quick start

import { readFileSync } from 'node:fs'
import {
  parseMiniGisExport,
  checkIfInAnyPolygon,
  findFirstCategoryContainingPoint,
} from 'mini-gis-geo'

const raw = readFileSync('./zones.json', 'utf8')
const data = parseMiniGisExport(raw)

const lat = 42.123456
const lng = 21.123456

const served = checkIfInAnyPolygon(lat, lng, data)
const zoneId = findFirstCategoryContainingPoint(lat, lng, data)
const zoneName =
  zoneId != null ? data.categories[String(zoneId)]?.name : null

Export JSON shape

The parser expects an object with at least:

| Field | Description | | --- | --- | | categories | Record of id (string key) → { id, name, color, ... } | | markers | Record of id (string key) → { id, categoryId, coords: { lat, lng } } |

Optional top-level fields (e.g. version, exportedAt, selectedCategoryId) are ignored by the geo logic but preserved on the parsed object.

Rings: For each categoryId, markers are ordered by ascending marker id to form one closed ring. At least three markers per category are required for polygon containment; fewer yield no fillable area for hit tests.

API

parseMiniGisExport(raw)

• Input: JSON string or already-parsed object.
• Output: The same object after validating categories and markers.
• Throws if JSON is invalid or required fields are missing.

Call once when loading your file; pass the result as data to everything below.

getCategoryIds(data)

Sorted array of numeric category ids present in categories.

getSortedMarkersForCategory(data, categoryId)

Markers for that category, sorted by marker id (ring order).

getCategoryPolygonXY(data, categoryId)

Vertices as { x, y } with x = lng, y = lat, or null if fewer than three markers.

latLngToXY(lat, lng) / isPointInPolygon(point, polygon)

• latLngToXY maps a WGS84 point to the plane used internally (x = longitude, y = latitude).
• isPointInPolygon is ray-casting on an array of { x, y } in order.

findCategoriesContainingPoint(lat, lng, data)

All category ids whose polygon contains the point (ascending id order). Can be empty or multiple if zones overlap.

checkIfInAnyPolygon(lat, lng, data)

true if the point lies inside at least one category polygon.

findFirstCategoryContainingPoint(lat, lng, data)

First matching category id, or null. When several polygons contain the point, this is the lowest category id among matches.

toRad(deg) / haversineMeters(lat1, lng1, lat2, lng2)

Radians helper and great-circle distance in meters between two WGS84 points.

findNearestPoint(lat, lng, data)

Nearest marker in the export by Haversine distance:
{ markerId, categoryId, distanceMeters, coords } or null if there are no markers.

Limitations

Containment uses latitude and longitude as Cartesian x/y (lng → x, lat → y). That matches the miniGis editor preview and is reasonable for city-scale zones. It is not a full spherical polygon library; for large geographic areas consider a dedicated GIS stack.

Development

From this package directory:

npm test

License

MIT