Geocoding Fundamentals

Geocoding converts addresses to geographic coordinates (latitude/longitude). Reverse geocoding does the opposite.

Forward Geocoding

Address → Coordinates

1"123 Main St, New York, NY 10001"
2        ↓
3{ lat: 40.7484, lng: -73.9967 }

Use cases:

• Plot customer locations on maps
• Calculate delivery distances
• Verify address existence

Reverse Geocoding

Coordinates → Address

1{ lat: 40.7484, lng: -73.9967 }
2        ↓
3"123 Main St, New York, NY 10001"

Use cases:

• Mobile app location sharing
• GPS coordinate conversion
• Location-based services

Free Geocoding APIs

Using Nominatim

javascript
1async function geocode(address) {
2  const url = new URL('https://nominatim.openstreetmap.org/search');
3  url.searchParams.set('q', address);
4  url.searchParams.set('format', 'json');
5  url.searchParams.set('limit', '1');
6
7  const response = await fetch(url, {
8    headers: { 'User-Agent': 'MyApp/1.0' }
9  });
10
11  const data = await response.json();
12
13  if (data.length === 0) return null;
14
15  return {
16    lat: parseFloat(data[0].lat),
17    lng: parseFloat(data[0].lon),
18    displayName: data[0].display_name
19  };
20}

Confidence Scores

Geocoding results include confidence indicators:

javascript
1function isHighConfidence(result) {
2  return result.importance > 0.6 &&
3         ['building', 'house'].includes(result.type);
4}

Best Practices

1. Normalize addresses first - Standardize before geocoding
2. Cache results - Coordinates rarely change
3. Handle failures - Graceful fallback
4. Respect rate limits - Don't get blocked
5. Validate results - Check confidence scores