> For the complete documentation index, see [llms.txt](https://docs.wisej.com/hybrid/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.wisej.com/hybrid/start/api/location/wisej.hybrid.shared.geolocation.altitudereferencesystem.md).

# AltitudeReferenceSystem

Namespace: **Wisej.Hybrid.Shared.Geolocation**

Assembly: **Wisej.Hybrid** (3.5.0.0)

Indicates the altitude reference system to be used in defining a location.

{% tabs %}
{% tab title="C#" %}

```csharp
public enum AltitudeReferenceSystem : Enum
```

{% endtab %}

{% tab title="VB.NET" %}

```visual-basic
Public Enum AltitudeReferenceSystem As [Enum]
```

{% endtab %}
{% endtabs %}

## Fields

| Name            | Description                                                                                                                                                        |
| --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| **Ellipsoid**   | The altitude reference system is based on an ellipsoid (usually WGS84), which is a mathematical approximation of the shape of the Earth.                           |
| **Geoid**       | The altitude reference system is based on the distance above sea level (parametrized by a so-called Geoid).                                                        |
| **Surface**     | The altitude reference system is based on the distance above the tallest surface structures, such as buildings, trees, roads, etc., above terrain or ground level. |
| **Terrain**     | The altitude reference system is based on distance above terrain or ground level                                                                                   |
| **Unspecified** | The altitude reference system was not specified.                                                                                                                   |

## Used By

| Name                                                                                                                               | Description                                                                                                                                                 |
| ---------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [Location.AltitudeReferenceSystem](/hybrid/start/api/location/wisej.hybrid.shared.geolocation.location.md#altitudereferencesystem) | Specifies the reference system in which the [Altitude](/hybrid/start/api/location/wisej.hybrid.shared.geolocation.location.md#altitude) value is expressed. |


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