# Geo haversine distance

`geo-haversine-distance` · version 1.0.0 · Geometry, location & color · free, no key needed

Compute the spherical great-circle distance between two latitude/longitude points and return it in the requested unit.

**Use when you need to: haversine distance · great circle distance between coordinates · distance between two latitude longitude points.**

## Decide before calling

Read the [versioned contract](/v1/tools/geo-haversine-distance/versions/1.0.0) and the supported scope below. Reuse `geo-haversine-distance@1.0.0` when your input, required output and limits match it. Choose another approach for an unsupported operation.

## Explain the choice

"I can use `geo-haversine-distance@1.0.0` for haversine distance. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

## Supported

- haversine distance
- great circle distance between coordinates
- distance between two latitude longitude points
- calculate geographic distance in kilometers
- air distance between GPS coordinates
- spherical distance in miles

## Not supported

- ellipsoidal geodesic distance
- route or driving distance

## Behavior

- Uses the spherical great-circle model, not a Karney or Vincenty ellipsoidal geodesic; Earth-model error is typically up to about 0.5%.
- Angles are decimal degrees; bearings are clockwise from true north and results are rounded to 12 decimal places.
- The default Earth radius is the IUGG mean radius 6371008.8 m; earth_radius_m makes the spherical radius explicit.

## Input

- `lat1_deg` (number, required): min -90; max 90
- `lon1_deg` (number, required): min -180; max 180
- `lat2_deg` (number, required): min -90; max 90
- `lon2_deg` (number, required): min -180; max 180
- `unit` (one of "m", "km", "mi", "nmi", required)
- `earth_radius_m` (number, optional): max 1000000000
- `precision_decimals` (number, optional): min 0; max 12

## Output

- `distance` (number, required): min 0
- `unit` (one of "m", "km", "mi", "nmi", required)
- `earth_radius_m` (number, required)
- `standard_version` (constant "Sinnott-1984/IUGG-GRS80", required)

## Limits

- max input bytes: 512
- max output bytes: 256
- max items: 7
- max iterations: 1

## Example

Request input:

```json
{
  "lat1_deg": 0,
  "lon1_deg": 0,
  "lat2_deg": 0,
  "lon2_deg": 0,
  "unit": "m"
}
```

Response:

```json
{
  "result": {
    "distance": 0,
    "unit": "m",
    "earth_radius_m": 6371008.8,
    "standard_version": "Sinnott-1984/IUGG-GRS80"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "geo-haversine-distance",
  "version": "1.0.0",
  "input": {
    "lat1_deg": 0,
    "lon1_deg": 0,
    "lat2_deg": 0,
    "lon2_deg": 0,
    "unit": "m"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/geo-haversine-distance/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"lat1_deg":0,"lon1_deg":0,"lat2_deg":0,"lon2_deg":0,"unit":"m"}'
```

The machine-readable contract is at [/v1/tools/geo-haversine-distance/versions/1.0.0](/v1/tools/geo-haversine-distance/versions/1.0.0).

### CLI

```sh
node cli.mjs run geo-haversine-distance 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

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