How do I get geospatial data from an API for a map app?

To get geospatial data from an API for a map app, the usual flow is:

1) Find an API that provides map data

Common sources:

• OpenStreetMap-based APIs: Overpass API, Nominatim
• Commercial map APIs: Google Maps, Mapbox, HERE, TomTom
• Government/open data APIs: city GIS portals, open data catalogs
• Your own backend: if you store locations, routes, boundaries, etc.

2) Decide what kind of geospatial data you need

Examples:

• Points: stores, users, landmarks
• Lines: roads, routes, trails
• Polygons: neighborhoods, parks, delivery zones
• Tiles: raster/vector map tiles for basemaps

3) Request the data from the API

Most geospatial APIs return:

• JSON / GeoJSON for features
• Protocol Buffers / vector tiles for map rendering
• XML sometimes for legacy APIs

Example: GeoJSON-style response

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": { "type": "Point", "coordinates": [-73.9857, 40.7484] },
      "properties": { "name": "Example Place" }
    }
  ]
}

4) Use the right query parameters

Typical parameters:

• bbox / bounds: map area to fetch
• lat, lng, radius: nearby search
• category: restaurants, parks, etc.
• zoom: for tile-based APIs
• limit: how many results to return

Example request:

curl "https://api.example.com/places?bbox=-74,40,-73,41"

5) Parse and convert it into map layers

If your map library is:

• Leaflet: add GeoJSON directly
• Mapbox GL JS: use GeoJSON sources or vector tiles
• Google Maps: convert to markers/polylines/polygons

Leaflet example

fetch('/api/places')
  .then(res => res.json())
  .then(data => {
    L.geoJSON(data).addTo(map);
  });

6) Handle common geospatial concerns

• Coordinate order: GeoJSON uses [longitude, latitude]
• Projection: most web maps use WGS84 / EPSG:4326 for data, Web Mercator for display
• Pagination / clustering: large datasets need clustering or viewport-based loading
• Caching: important for performance
• API rate limits: many APIs restrict requests

7) If you’re building a production map app

Best practices:

• Load data only for the current viewport
• Use clustering for many points
• Cache responses by tile or bounding box
• Prefer vector tiles for large datasets
• Validate and sanitize API data
• Store API keys securely on the backend

Simple architecture

1. User pans/zooms map
2. App gets current bounds
3. App requests API data for that bounds
4. API returns GeoJSON/features
5. App renders features on the map

If you want to build your own API

A common stack:

• Database: PostGIS
• Backend: FastAPI / Node / Django / Go
• Format: GeoJSON or vector tiles
• Frontend: Leaflet / Mapbox GL / OpenLayers

If you want, I can show you:

1. a Leaflet example,
2. a Mapbox GL example, or
3. how to design your own geospatial API.