#### Positioning Sensor Operational Features

Positioning sensor data is recalculated by ECDIS taking into account the receiver offset relative to the vessel's CCRP, and is displayed in the {doc}`**Navigational Panel** </sections/graphical-user-interface/navigational-panel/index>` and the {doc}`**Log book** </sections/navigational-log/standard-position/index>`.

The vessel's course vector is constructed from the positioning sensor data. For vector display settings, see the {doc}`**Vectors and Trajectory** </sections/vessel-settings/vectors-and-trajectory/index>` section. The course vector is constructed from the CCRP set in {doc}`vessel dimensions </sections/vessel-settings/vessel-dimensions/index>`.

If **Differential receiver** is enabled in the GNSS receiver settings, but the differential signal receiver is absent — ECDIS will generate a **Differential signal lost** warning (see table). The coordinate, COG, and SOG fields on the navigational panel will be highlighted in yellow.

![Navigation Panel](images/GNSS_1.png)

| No. | Field | Description |
|---|---|---|
| 1 | Coordinates | Coordinates received from the GNSS receiver. Coordinate system **WGS 84**. Received from sentences: `$--RMC`, `$--GLL`, `$--GNS` |
|   | **POS** | Navigation parameter type — positioning |
|   | **GLONASS** | Name of the sensor providing the data |
|   | **Diff** | Sensor operating mode indicator |
| 2 | Date/Time | Ship date and ship time, adjusted for the {doc}`time zone </sections/system-settings/measurement-units/index>`. Received from sentences: `$--RMC`, `$--ZDA` |
| 3 | **RMS** | Root mean square error of position determination. Received from sentence: `$--GSA`. |
```{important}
When switching to dead reckoning mode, it is recommended to calculate RMS and enter it manually after each manual observation
``` 
||||
|---|---|---|
| 4 | Course over ground | Course over ground received from the GNSS receiver. Received from sentences: `$--RMC`, `$--VTG`, `$--GNS` |
|   | **COG** | Navigation parameter name |
|   | **GLONASS** | Name of the sensor providing the data |
| 5 | Speed over ground | Speed over ground received from the GNSS receiver. Received from sentences: `$--RMC`, `$--VTG`, `$--GNS` |
|   | **SOG** | Navigation parameter name |
|   | **GLONASS** | Name of the sensor providing the data |

#### Position Discrepancy

When two or more position sensors are connected to ECDIS, the discrepancy between the Primary and Secondary sensors will be calculated.

![Misclousure POS](images/Misclousure_1.png)

| No. | Element | Description |
|---|---|---|
| 1 |  | Primary position sensor with priority **0** |
| 2 |  | Secondary position sensor with priority **1** |
| 3 |  | Secondary position sensor coordinates |
| 4 | Discrepancy | Direction and distance between Primary and Secondary positions |
| 5 | **DR misclousure** | Display Secondary position on the ENC. Hide Secondary position — press again |

![Misclousure POS ENC](images/Misclousure_2.png)

| No. | Element | Description |
|---|---|---|
| 1 | Primary position | Based on data from Position sensor with priority **0** |
| 2 | Secondary position | Based on data from Position sensor with priority **1** |

#### Position Sensor Warnings

| Text | Category | Condition |
|---|---|---|
| Position (COG/SOG) error: \<sensor name\> | Warning | When data from the sensor stops being received according to the configurable timeout. |
| HDOP exceeded: \<sensor name\> | Caution | When the **HDOP (Horizontal Dilution of Precision)** parameter value is greater than 4. Operates only when the GNSS receiver transmits `$--GSA`, `$--GNS` messages. |
| No GNSS fix: \<sensor name\> | Warning | Mode indicator in the message has value N (No fix) for packets: `$--RMC`, `$--GLL`, `$--GNS`. |
| Position lost: \<sensor name\> | Alarm | Positioning system mode indicator has value E in messages: `$--RMC`, `$--GLL`, `$--GNS`, or when unable to obtain latitude/longitude from any packet: `$--RMC`, `$--GLL`, `$--GNS`. |
| Differential signal lost: \<sensor name\> | Warning | Positioning system mode indicator transitions from value D to any other value in messages: `$--RMC`, `$--GLL`, `$--GNS`, or when unable to obtain latitude/longitude from any packet: `$--RMC`, `$--GLL`, `$--GNS`. |
| Differential corrections not applied: \<sensor name\> | Warning | Age of differential GPS data indicator. GNSS data staleness indicator in differential mode in `$--GGA`, `$--GNS` messages — empty field. If the receiver was previously in differential mode |
| GNSS data integrity violation: \<sensor name\> | Warning | If the sentence fails the CRC check. |
| Coordinate discrepancy | Warning | If data from the `$--DTM` sentence is absent or the `$--DTM` sentence transmits a coordinate system other than **WGS 84** |
