Generate GeoJSON

@orbat-mapper/control-measures is a pure function library: give it a control-measure kind, a list of input points, and an options object, and it returns MIL-STD-2525 / APP-6 tactical graphics as plain GeoJSON Features. No map engine, no canvas, no framework — works in a browser, a Node service, a test, or an SVG pipeline like the catalog previews.

Install

npm install @orbat-mapper/control-measures

Render a control measure

renderControlMeasure(measure, options?) is the single entry point. A ControlMeasure is { id, kind, controlPoints, options? } — id is your stable identifier, kind selects the measure, and controlPoints are [lon, lat] pairs.

import { renderControlMeasure } from "@orbat-mapper/control-measures";

const render = renderControlMeasure({
  id: "ambush-1",
  kind: "ambush",
  controlPoints: [
    [-0.871, 49.369],
    [-0.861, 49.369],
    [-0.866, 49.374],
  ],
});

// `render` is a GeoJSON FeatureCollection you can hand to any map.
render.features.forEach((f) => console.log(f.geometry.type));

Each output feature carries a properties.part tag (which piece of the graphic it is) and a resolved properties.style. Stable feature ids follow ${id}:${part}:${index}, so you can reconcile renders across edits.

How many points does a control measure need?

Every kind declares a point contract — a minimum (and sometimes maximum) number of input coordinates. Below the minimum, the render is empty rather than throwing. Read the contract from the metadata:

import {
  listControlMeasureMetadata,
  getControlMeasureMetadata,
} from "@orbat-mapper/control-measures";

// Every measure, with geometry, point contract, params, and symbology.
const all = listControlMeasureMetadata();

const ambush = getControlMeasureMetadata("ambush");
ambush.minCoordinates; // 3
ambush.geometry; // "line"

The catalog is generated from exactly this metadata. See it for the full list of kinds and their point contracts.

Options and defaults

Most measures expose tuning parameters (head size, tooth count, fill, …). Each kind ships defaults; fetch them with getDefaultOptions and override what you need.

import { getDefaultOptions, renderControlMeasure } from "@orbat-mapper/control-measures";

const options = { ...getDefaultOptions("ambush"), arrowheadLengthRatio: 0.25 };

const render = renderControlMeasure({
  id: "ambush-1",
  kind: "ambush",
  controlPoints,
  options,
});

Parameters per kind — keys, types, and defaults — are in the catalog. For colors and stroke, see Styling.

Validation

An invalid input (too few points, non-finite coordinates) yields an empty render silently by default. Pass validationMode when you'd rather be told:

renderControlMeasure(measure, { validationMode: "warn" }); // "silent" | "warn" | "throw"