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# verticalAccuracy

The validity of the altitude values, and their estimated uncertainty, measured in meters.

```
var verticalAccuracy: CLLocationAccuracy { get }
```

## Discussion

A positive [`verticalAccuracy`](/documentation/CoreLocation/CLLocation/verticalAccuracy) value represents the estimated uncertainty associated with [`altitude`](/documentation/CoreLocation/CLLocation/altitude) and [`ellipsoidalAltitude`](/documentation/CoreLocation/CLLocation/ellipsoidalAltitude). This value is available whenever altitude values are available.

If [`verticalAccuracy`](/documentation/CoreLocation/CLLocation/verticalAccuracy) is `0` or a negative number, [`altitude`](/documentation/CoreLocation/CLLocation/altitude) and [`ellipsoidalAltitude`](/documentation/CoreLocation/CLLocation/ellipsoidalAltitude) values are invalid. If [`verticalAccuracy`](/documentation/CoreLocation/CLLocation/verticalAccuracy) is a postive number, [`altitude`](/documentation/CoreLocation/CLLocation/altitude) and [`ellipsoidalAltitude`](/documentation/CoreLocation/CLLocation/ellipsoidalAltitude) values are valid.

A positive [`verticalAccuracy`](/documentation/CoreLocation/CLLocation/verticalAccuracy) value represents an uncertainty that’s approximately 68 percent, or one standard deviation, above and below the altitude values.

> Note:
> In iOS, this property is declared as `nonatomic`. In macOS, it’s declared as `atomic`.

---

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