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Geospatial Queries

ZiWound's interactive map is powered by MongoDB geospatial queries over the report model's GeoJSON point field. This page is a focused look at the geo side — it builds directly on the Report model and the Search & Indexes pages.

The data model​

A report carries a GeoJSON Point — longitude/latitude, in that order:

// report.ts
point: geoJSONStruct("Point"),   // { type: "Point", coordinates: [lng, lat] }

geoJSONStruct comes from the mongodb driver's schema types (re-exported through npmDeps). The index must be 2dsphere for GeoJSON queries:

await db.collection("report").createIndex({ point: "2dsphere" });

The act — getRelatedByGeo​

Source: back/src/report/getRelatedByGeo/.

export const getRelatedByGeoFn: ActFn = async (body) => {
  const { set } = body.details;
  const { center, radiusKm } = set;

  // $centerSphere takes radius in RADIANS: kilometers / earth's radius
  const filter = {
    point: {
      $geoWithin: { $centerSphere: [center, radiusKm / 6371] },
    },
  };
  if (set.status) filter.report_status = set.status;
  if (set.searchTerm) filter.$text = { $search: set.searchTerm };

  return await reports.find({ filter, projection: get, limit, skip });
};

Validator shape:

export const getRelatedByGeoValidator = () =>
  object({
    set: object({
      center: array(number()),        // [lng, lat]
      radiusKm: number(),
      status: optional(enums(report_status_array)),
      searchTerm: optional(string()),
      limit: optional(number()),
      skip: optional(number()),
    }),
    get: coreApp.schemas.selectStruct("report", { ... }),
  });

How the frontend drives it​

The map (MapLibre GL + Leaflet) listens for a viewport change, computes the visible center + radius, and calls getRelatedByGeo. Because the act returns approved reports by default, the frontend passes status: "Approved" to keep pending reports off the public map.

// front/src/app/[locale]/map/... (simplified)
const { docs } = await callLesan("getRelatedByGeo", {
  set: { center: mapCenter, radiusKm: visibleRadius, status: "Approved" },
  get: { title: true, point: true, report_status: true },
});

Key takeaways​

  • geoJSONStruct("Point") + 2dsphere index is all Lesan needs for geospatial — there's no Lesan-specific geo API, just the MongoDB field type and index.
  • Radians math: $centerSphere radius is in radians; the act converts km (km / 6371).
  • Composable filters — geospatial, text, and status filters combine in one filter object, so map search and text search work together.
  • Reuse the same projection — the act's get validator reuses selectStruct("report", ...), so the client controls exactly what each map marker carries.

Next: File Uploads.