## Bearing and Distance Measurement (ERBL)

The **ERBL (Electronic Bearing and Range Line)** tool is designed to measure directions (bearings) and distances from the vessel to an arbitrary point, or between two arbitrary points on the chart.

### Tool activation

The tool is activated by clicking the ERBL icon ![ERBL](images/erbl-icon.png) in the tool selection menu. When activated, the ECDIS cursor changes to ![ERBL cursor](images/erbl-cursor.png).

```{important}
**In bearing and distance measurement mode, chart panning is blocked!**
```

### Measuring bearing and distance from the vessel

To measure the bearing and distance from the current vessel position, left-click (tap) the point of interest on the chart.

![Measurement from vessel](images/ERBL_1.png)

**Features:**
- The bearing is measured from the current vessel position to the selected point
- The distance is calculated automatically
- If the mouse button is released (finger lifted), the **initial point resets** to the vessel position

### Measuring between two points

To measure between two arbitrary points on the chart:

1. Press and hold the left mouse button at the first point
2. Drag the cursor to the second point
3. Release the mouse button

![Measurement between points](images/ERBL_2.png)

### Measurement parameters

| Parameter | Description |
|----------|----------|
| **Bearing** | The angle between the north direction and the measurement line (in degrees). Forward direction (`T`) — from the vessel to the point, and reverse direction (`R`) — from the point to the vessel.<br><br> When measuring between two arbitrary points, only the forward direction from the first point to the second is displayed |
| **Distance** | The distance between the measurement points (in nautical miles, meters, or kilometers) |
| **Origin point** | The vessel position or the first selected point on the chart |
| **Endpoint** | The selected measurement point |

```{note}
The **ERBL** line type is always a great circle (GC).
```

### Operating features

**Measurement modes:**
- **From vessel:** click a point on the chart — measurement from the current vessel position
- **Between points:** press and drag — measurement between two arbitrary points

**Indication:**
- The measurement line is displayed on the chart
- Measurement parameters (bearing and distance) are shown in the information window or on the chart

**Reset:**
- Releasing the mouse button without dragging returns to the origin point (vessel position)
- To start a new measurement, simply select a new point

```{tip}
**Use the ERBL tool for rapid estimation of distances and directions when planning maneuvers or working with navigational objects on the chart.**

For accurate measurements, select points on the chart considering the current scale — the larger the scale, the more accurate the measurement.
```

```{note}
The ERBL tool is an indispensable means for performing navigational calculations and assessing the situation on the chart without the need to construct complex graphical plots.
```
