# Echo sounders

You can connect Trimble Access to an echo sounder and use it to measure the depth of positions on the sea floor or objects under water. The depth information is stored with the point. You can generate reports of continuous topo points stored in Trimble Access with the depth applied.

Storing depth measurements from the echo sounder is supported only when using the Continuous topo measurement method during a conventional or GNSS survey.

To configure the echo sounder

Trimble Access supports a number of echo sounder models as standard. An ESD file for each supported echo sounder is installed in the C:\ProgramData\Trimble\Trimble Data\System Files folder when you install the Trimble Access software. Alternatively, you can download them from the Template files page of the Trimble Access Help Portal.

To edit the ESD file, edit the file in a text editor. The name of the ESD file appears in the Type field in the Echo Sounder screen.

Trimble Access supports as standard the following models of bathymetric echo sounders:

- CeeStar Basic High Freq

  CeeStar Dual Frequency echo sounders, BASIC output format, when the High Frequency depth is to be stored. The unit must be set to output 'prefixes' and not 'commas' in the output data Menu / Advanced / Prefix / Comma outfm set to [Use prefix].

- CeeStar Basic Low Freq

  CeeStar Dual Frequency echo sounders, BASIC output format, when the Low Frequency depth is to be stored. The unit must be set to output 'prefixes' and not 'commas' in the output data Menu / Advanced / Prefix / Comma outfm set to [Use prefix].

- NMEA SDDBT device

  Any generic echo sounder device that can output the NMEA DBT (Depth Below Transducer) sentence. The "talker ID" must send the standard "SD" identifier (so that output lines all begin with "$SDDBT,..". Trimble Access will accept the data in feet, meters, or fathoms and will convert values as appropriate.

- SonarMite

  Any SonarMite device. The unit will be switched into 'Engineering mode' (output format 0) and other settings may be adjusted by Trimble Access.

When using an echo sounder to record depths that equal zero, you need to add the allowZero="True" flag immediately after the isDepth="True" flag. For example: "<Field name... isDepth="True" allowZero="True" />"

NMEA strings for echo sounders

Echo sounders may output one of several NMEA 0183 sentences. The most common sentences are described below for reference.

NMEA DBT – Depth Below Transducer

The NMEA DBT sentence reports water depth referenced to the transducer's position. The depth value is expressed in feet, meters, and fathoms.

For example: $xxDBT,DATA_FEET,f,DATA_METRES,M,DATA_FATHOMS,F*hh<CR><LF>

NMEA DBS – Depth Below Surface

The NMEA DBS sentence reports water depth referenced to the surface. The depth value is expressed in feet, meters, and fathoms.

For example: $xxDBS,DATA_FEET,f,DATA_METRES,M,DATA_FATHOMS,F*hh<CR><LF>

To add support for another model of echo sounder

The Trimble Access software uses XML Echosounder protocol description (*.esd) files and so may support bathymetric echo sounders that are not supported as standard, provided that their communications protocols are similar to the protocols currently supported. To do this, download one of the additional ESD templates provided or use one of the ESD files installed with the software and use it as a template. You will need to find out the format for your echo sounder and modify the ESD file accordingly.

You can download additional ESD templates from the Template files page of the Trimble Access Help Portal.

To configure echo sounder settings in the survey style

1. Tap and select Settings / Survey styles / <Style name>.
2. Tap Echo sounder.
3. Select an instrument from the Type field.
4. Configure the Controller port:
   - If you set the Controller port to Bluetooth, you must configure the echo sounder Bluetooth settings.
   - If you set the Controller port to COM1 or COM2, you must configure the port settings.

5. If required, enter the Latency value.

   The latency caters for echo sounders where the depth is received by the controller after the position. The Trimble Access software uses the latency to match and store the depth when it is received with continuous topo points that were saved previously.

   There are many factors involved in correctly pairing positions with accurate depths. These include sound velocity – which varies with water temperature and salinity, hardware processing time, and the speed at which the boat is moving. Make sure that you use the appropriate techniques to achieve the required results.

6. If required, enter the Draft value.

   The Draft affects how the antenna height is measured. If the Draft is 0.00 then the antenna height is the distance from the transducer to the antenna. If a Draft is specified, then the antenna height is the distance from the transducer to the antenna, minus the draft.

7. Tap Accept.
8. Tap Store.

To connect to the echo sounder

To connect to the echo sounder, enable Bluetooth on the echo sounder. In Trimble Access, tap and select Settings / Connections and then select the Bluetooth tab to scan for devices and pair with the echo sounder. The default PIN to pair with the Ohmex SonarMite echo sounder is 1111. For more information, see Bluetooth connections.

To store depths using an echo sounder

1. Connect the echo sounder to the controller using a cable or Bluetooth.
2. Configure the Echo sounder settings in the survey style.
3. To store depths with measured points, use the continuous topo method for your survey type.

   The depth is displayed in the Continuous topo screen and in the map. If you have configured a Latency value in the survey style, the continuous topo points are initially stored without depths and later updated. When a latency has been configured, the depth that is displayed is an indicator that depths are being received but it may not be the depth that is stored with the point name that is displayed at the same time.

4. To change Latency and Draft values, tap Options. For more information, see To configure echo sounder settings in the survey style.

5. To disable storing depths with continuous topo points during the survey, tap Options and then clear the Use echo sounder check box.

To generate reports that include depths

The elevations of continuous topo points stored in Trimble Access do not have the depth applied to them. Use Export custom format files to generate reports with depths applied.

The following report stylesheets are available for download:

- Comma Delimited with elevation and depths.xsl
- Comma Delimited with depth applied.xsl

These stylesheets can be downloaded from the Stylesheets page of the Trimble Access Help Portal.

If a Sonarmite instrument is connected, Trimble Access configures it to use the correct output format and mode. For an instrument from another manufacturer, you must manually configure it to use the correct output format.