Source: https://maps.vietmap.vn/docs/map-api/geofencing/

# Geofencing API

[![geofencing]][geofencing]
[geofencing]: https://maps.vietmap.vn/docs/assets/geofencing-jpg.webp

**Geofencing** means checking whether a position falls inside a virtual boundary drawn around a real-world place. The VIETMAP Geofencing API takes a position (vehicle, device) together with a list of zone centers and a radius in metres, and returns `inside: true/false` per center. Each request is an independent check: the API stores no fences and emits no events. To detect enter/exit, call it on every position update and compare with the previous result.

## What you can build with it

| Use case | What the geofence does |
| --- | --- |
| **Proof of delivery** | Confirm the vehicle actually reached the customer address before the driver marks the order delivered. |
| **Fleet compliance** | Alert when a truck leaves its permitted operating zone or enters a restricted district. |
| **Automatic trip records** | Start and stop a trip when a vehicle leaves and returns to the depot, without the driver touching anything. |
| **Site attendance** | Record staff arriving at and leaving a construction site or branch. |
| **Proximity marketing** | Notify a customer when they are near one of your stores. |
| **Asset protection** | Raise an alarm the moment equipment moves outside the yard it belongs to. |

## Geofence vs. isochrone

A **geofence** is a zone *you* define by center and radius and check positions against. An **[isochrone](https://maps.vietmap.vn/docs/map-api/isochrone/)** is a boundary VIETMAP *computes* — the area reachable within a given travel time. They pair naturally: compute an isochrone to decide what a sensible serving area looks like, then use that area's center and an approximate radius as the geofence.

URL
---
```swift
https://maps.vietmap.vn/api/geofencing?apikey={your-apiKey}

```

Method
---
**POST**
 
Parameters
---
|Parameter|Type|Required|Default|Description|
|--- |--- |--- |--- |--- |
|apikey|string|yes|none|API key provided by VIETMAP for your account. [Register here](https://maps.vietmap.vn/console-v2/register)|


Example
---

```swift
URL:
https://maps.vietmap.vn/api/geofencing?apikey=”YOUR APIKEY”
```
```json
Body:
{
    "geometryCenters": 
    [
        {
            "id": "1",
            "long": 105.7487405,
            "lat": 9.8644254
        },
        {
            "id": "2",
            "long": 105.7491342,
            "lat": 9.8642686
        },
        {
            "id": "3",
            "long": 105.7489267,
            "lat": 9.8645398
        }
    ],
    "radius": 15,
    "long": 105.7488398,
    "lat": 9.8643837
}
```
### Request body description
| Parameter        | Type    | Description                                                            |
|------------------|---------|------------------------------------------------------------------------|
| geometryCenters | array   | Centers of the zones to check against, one object per zone. |
| geometryCenters.id | string | The identifier of the geometry center.                                 |
| geometryCenters.long | number | The longitude coordinate of the geometry center.                       |
| geometryCenters.lat  | number | The latitude coordinate of the geometry center.                        |
| radius           | number  | Radius in metres, applied to every center in `geometryCenters`. `inside` is `true` when the position is within `radius` of the center. |
| long             | number  | Longitude of the position to check (vehicle, device).                  |
| lat              | number  | Latitude of the position to check (vehicle, device).                   |


Response
---

```json
{ 
    "code": null,
    "message": null,
    "data": [
        {
            "id": "1",
            "inside": true
        },
        {
            "id": "2",
            "inside": false
        },
        {
            "id": "3",
            "inside": false
        }
    ]
}
```

### Response description
| Field      | Type    | Description                                                          |
|------------|---------|----------------------------------------------------------------------|
| code       | null    | Error code. `null` on success.                                       |
| message    | null    | Error message. `null` on success.                                    |
| data       | array   | One entry per center in `geometryCenters`.                           |
| data.id    | string  | The `id` you sent for this zone.                                     |
| data.inside| boolean | `true` if the position is within `radius` of this center, otherwise `false`. |