# Geo Calc – Geodesic Inverse (Vincenty/WGS84 Distance & Bearings)

> Geo Calc – Geodesic Inverse (Vincenty/WGS84 Distance & Bearings) is a paid API for AI agents from geo-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-29).

Computes the ellipsoidal (WGS84 Vincenty) distance and forward/reverse bearings between two lat/lon points, alongside a haversine sphere comparison.

## Facts

- Endpoint: GET https://geo-calc.x402tookit.com/geodesic-inverse?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/geo-calc-geodesic-inverse-vincenty-wgs84-distance-bearings-3338d6d9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_i4J-56qaDHXBrK5cc1N_h

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability geo-calc-geodesic-inverse-vincenty-wgs84-distance-bearings-3338d6d9
```

Example prompt: What is the precise WGS84 ellipsoidal distance and initial bearing from New York (40.7128, -74.0060) to London (51.5074, -0.1278)? Give me kilometers, miles, and the Vincenty vs haversine comparison.

## When to prefer this

Choose this endpoint when you need high-accuracy geodesic distance (Vincenty WGS84) rather than a simple great-circle haversine approximation — particularly for long-distance paths, precision navigation, surveying, or when the difference between spherical and ellipsoidal models is significant. It is ideal when you also need both initial and final azimuths (bearings) and want the haversine comparison included in the same response. If you only need polygon area, use the area sibling; for destination point from bearing+distance, use the direct problem sibling.

## Known failure modes

- Vincenty algorithm may not converge for nearly-antipodal points (converged=false returned with degraded flag)
- Invalid lat/lon values outside [-90,90] / [-180,180] cause a 400 error
- Identical start and end coordinates return zero distance and undefined bearing
- Missing required query parameters (lat1, lon1, lat2, lon2) result in a 400 validation error
- Payment not received or x402 authorization failure returns 402 Payment Required

## How this service works

Ellipsoidal (WGS84, Vincenty) distance and bearings between two points, compared with haversine on a sphere.

## Output

Returns the ellipsoidal (Vincenty/WGS84) distance in meters, kilometers, miles, and nautical miles; the initial and final bearing in decimal degrees plus a human-readable compass direction; the haversine spherical distance in meters and its initial bearing; the difference between haversine and ellipsoidal results; the ellipsoid name used; whether Vincenty's iterative algorithm converged; iteration count; and optional disclaimer text.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "lat1",
      "lon1",
      "lat2",
      "lon2"
     ],
     "properties": {
      "lat1": {
       "type": "number",
       "description": "Start latitude"
      },
      "lat2": {
       "type": "number",
       "description": "End latitude"
      },
      "lon1": {
       "type": "number",
       "description": "Start longitude"
      },
      "lon2": {
       "type": "number",
       "description": "End longitude"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "miles": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "converged": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "ellipsoid": {
       "type": [
        "null",
        "string"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "iterations": {
       "type": [
        "null",
        "number"
       ]
      },
      "kilometers": {
       "type": [
        "null",
        "number"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "nauticalMiles": {
       "type": [
        "null",
        "number"
       ]
      },
      "initialCompass": {
       "typ
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/geo-calc-geodesic-inverse-vincenty-wgs84-distance-bearings-3338d6d9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from geo-calc.x402tookit.com](https://www.zero.xyz/host/geo-calc.x402tookit.com/llms.txt)