Snap to Road

POST/routing/snap

Snap GPS coordinates to the nearest road segment. Corrects GPS drift and ensures coordinates align with the road network.

Request Body

Field	Type	Required	Description
`coordinates`	Coordinates[]	Yes	Array of GPS coordinates to snap
`radius`	number	No	Maximum snap distance in meters (default: 50)

Coordinates

Field	Type	Required	Description
`lat`	number	Yes	Latitude
`lng`	number	Yes	Longitude

{ "lat": 40.7128, "lng": -74.0060 }

Example Response

{
  "snapped": [
    {
      "location": { "lat": 40.712801, "lng": -74.005982 },
      "originalIndex": 0,
      "distance": 2.3,
      "name": "Broadway"
    },
    {
      "location": { "lat": 40.713512, "lng": -74.005791 },
      "originalIndex": 1,
      "distance": 1.8,
      "name": "Broadway"
    },
    {
      "location": { "lat": 40.714198, "lng": -74.005489 },
      "originalIndex": 2,
      "distance": 2.1,
      "name": "Broadway"
    }
  ],
  "unsnapped": []
}

Response Fields

Field	Type	Description
`snapped`	SnappedPoint[]	Successfully snapped coordinates
`unsnapped`	number[]	Indices of points that couldn't be snapped within radius

SnappedPoint

Field	Type	Description
`location`	Coordinates	Snapped position on road
`originalIndex`	number	Index in the original input array
`distance`	number	Distance from original point in meters
`name`	string	Road name (if available)

Use Cases

GPS Correction: Fix inaccurate GPS readings from mobile devices
Route Reconstruction: Convert raw GPS traces to road-following paths
Address Validation: Ensure pickup/dropoff coordinates are on valid roads
Map Matching: Align vehicle positions to the road network for tracking

Handling Unsnapped Points

Points that cannot be snapped within the specified radius are returned in the unsnapped array. This can happen when:

The point is too far from any road
The point is in an area without road coverage
The radius is set too small

{
  "snapped": [
    {
      "location": { "lat": 40.712801, "lng": -74.005982 },
      "originalIndex": 0,
      "distance": 2.3
    }
  ],
  "unsnapped": [1, 2]
}

In this example, points at indices 1 and 2 could not be snapped.

Best Practices

Use a radius of 50-100m for typical GPS accuracy
For high-accuracy GPS (RTK/DGPS), use a smaller radius (10-20m)
Process coordinates in batches for efficiency
Handle unsnapped points gracefully in your application

On this page