## ARPA Setup

The sensor connection and setup are performed in accordance with the {doc}`procedure </sections/sensors/navigation-sensors/index>`.

| Menu path |
|-------------|
| {{ menu }} → {{ settings }} → Sensors → ARPA |

Ensure that received message processing is correctly configured, header and message processing is enabled, and checksum verification is enabled.

ARPA transmits the following IEC 61162 sentence header:
- **RA** — Radar;

#### Recommended ARPA Sentences

![ARPA Sentences](images/ARPA_1.png)

- `$--RSD` – Radar system data;
- `$--TLB` – Target label;
- `$--TLL` – Target latitude and longitude;
- `$--TTD` – Tracked target data;
- `$--TTM` – Tracked target message.


```{important}
If messages are not transmitted in the correct format or are transmitted with incorrect data, the display and processing of ARPA targets will not be possible.

**Data transmission settings are configured in ARPA, not in ECDIS.**
```
```{tip}
After connecting and configuring ARPA, enable the {doc}`ARPA layer </sections/graphical-user-interface/operational-settings/index>`.
```

#### Target Association Setup

![ARPA Sentences](images/ARPA_Settings.png)

| No. | Parameter | Description |
|---|----------|----------|
| 1 | **Supports targets association** | Target association indicator in the ARPA sensor |

```{caution}
Depending on the model, the radar may or may not support target association. Target association may be disabled in the radar by the user. Target association in the radar may not work for other reasons.
```
When configuring the ARPA sensor, specify whether the sensor supports target association:
 1. Checkbox disabled — the sensor does not support target association. In this case, ECDIS independently performs association of targets received from ARPA (radar) and AIS.
 2. Checkbox enabled — the sensor supports target association. In this case, ECDIS displays associated targets received from ARPA. ECDIS internal target association is disabled.

```{caution}
Incorrect ARPA sensor association settings may cause target duplication: the targets table and the screen will always display two targets instead of one associated target: an ARPA target and an AIS target.
```