Displaying speed though water and distance through water data

[Chuck - Raymarine - Moderator]

Displaying speed though water and distance through water data

Two types of speed/distance can be displayed by Raymarine's MFDs:
- GPS speed over ground (SOG) / distance (Ground Log, Ground Trip 1-4) over ground and
- speed through water (Speed) / distance through water (Log, Trip).

If you are be satisfied with GPS speed/distance over ground, then no additional sensors need be installed to a MFD which is receiving a GPS position FIX. The MFD would simply need to be configured to display SOG, Ground Log, and Ground Trip within the Databar, within a Data application panel, or within Databoxes. However, if you desire to view speed/distance through water, then a speed instrument or a compatible fishfinder transducer with speed through water transducer (may be included in the depth transducer or the depth transducer may be accessorized with a compatible speed/temp transducer) must be installed.

Speed through water (Speed) is particularly useful in conjunction with SOG in determining through water efficiency calculations as well for trolling and sailing applications. Should the the currently installed fishfinder transducer not support speed through water (i.e. it does not feature a paddle wheel), then speed through water may be added by added to the system by:
- replacing the currently installed fishfinder transducer with a compatible depth/speed/temperature fishfinder transducer
- interfacing the currently installed transducer to a compatible fishfinder speed/temp transducer
- interfacing the MFD to a speed sensing instrument system (ex. i40 Speed/Bidata, i50 Speed/Tridata, i70 MFID w/iTC-5 and instrument speed/temperature transducer).

Most sailboats or vessels operating for extended periods of time on battery would be advised to install a speed instrument as the fishfinder sonars draw more current. Installing a fishfinder sonar module with a fishfinder depth/speed/temp transducer will enable a greater number of features than would be offered by installing a speed instrument alone (most notably bottom/structure imaging and fish location).

If speed is provided by the fishfinder transducer, then the speed must be calibrated (HOME->FISHFINDER->MENU->SET-UP->TRANSDUCER SET-UP->SPEED OFFSET). If speed is provided by an instrument, then it must be calibrated via the instrument display. Failure to calibrate speed will cause the through water speed / log / trip and GPS speed / GPS log / GPS trip values to differ when not operating under influence of current (ex. slack tide, on lake, etc.). Additionally, products supporting single point speed calibration (ex. fishfinding products, i40 Speed/Bidata, i50 Speed/Tridata, ST40 Speed/Bidata, ST60 Speed/Tridata, etc.) will most accurately report speed and trip when the vessel is operating at the speed at which the the speed sensor was calibrated. For those seeking the most accurate speed and trip values, it is recommended that an instrument supporting multi-point speed through water calibration and an instrument speed through water transducer should be included within the system. SOG and Speed will always differ due to the effects of leeway. Similarly, GPS trips and GPS logs will always differ due to the effects of leeway. In the most extreme example should a vessel be drifting in a strong current, then SOG, GPS Trips, and GPS Log will respond to the movement of the vessel. However, when so drifting, the Speed, Trip, and Log values may indicate little or no movement relative to the water, as the vessel's reported speed relative to the water (i.e. current) would be zero.

Please note that log/trip will generally differ from GPS log / GPS Trip due to affects of current. Under slack conditions, calibrated log / trip should be fairly close in value to GPS log / GPS Trip. Speed through water sensors feature non-linear error. As such, these sensors will be most accurate at the speed that the are calibrated at. Hi performance instruments (ex. i70, ST70, ST290) feature multi-point speed though water calibration, while fishfinders and some instruments (ex. i40 Speed/Bidata, i50 Speed/Tridata, etc.) feature single-point speed through water calibration.

With respect to resetting these log and trip distances:
- Ground Log: designed to run continuously, much like a vehicles odometer ... may be reset only by executing the System Settings Reset (HOME->SET-UP->MAINTENANCE->SYSTEM SETTINGS RESET) or System Settings and Data Reset (HOME->SET-UP->MAINTENANCE->SYSTEM SETTINGS & DATA RESET) commands ... these will reset all of the system's settings and the latter will additionally cause all waypoints, routes, and tracks stored within the MFD's memory (excluding those saved onto memory cards) to be deleted.
- Ground Trip 1 - 4: may be reset via the command sequence HOME->SET-UP->TRIP RESETS->GROUND TRIP 1-4 RESET
- Log: designed to run continuously, much like a vehicles odometer ... may be reset only by resetting the fishfinder sonar module is providing speed data to the system or by commanding the a factory reset to the instrument which is providing speed data to the system
- Trip: may be reset via the command sequence HOME->SET-UP->TRIP RESETS->TRIP RESET should a fishfinder sonar module is providing speed data to the system
or by a Trip Reset command on the instrument which is providing speed data to the system

It is recommended that one verify that the MFD's Fishfinder application settings have been properly configured to specify the model of transducer installed (HOME->FISHFINDER->MENU->SET-UP->TRANSDUCER SET-UP->TRANSDUCER) (EX. B744V/B744VL, P58/P65/P66, etc). When interfaced to a B744V, B744VL, P58, P65, or P66 transducer, the Speed Transducer configuration setting (HOME->FISHFINDER->MENU->SET-UP->TRANSDUCER SET-UP->SPEED TRANSDUCER) should be configured to "DEFAULT".

The a/c/e/eS/gS-Series MFDs support the following three options for showing Speed (through water) within your system:
- Customize the MFD's Databar to add Water Temperature
- Configure the application to display a Databox which has been configured to display Water Temperature
- Customize one of data cells within a Data application data panel to display Water Temperature.

Information concerning these data related features maybe found within the LightHouse II Release 19 Operating Instructions.

The procedures below specifies how a Databox may be displayed and then populated with the Water Temp data item. Detailed instructions may be found within Chapter 5.6 Databar and databox overview of the LightHouse II Release 19 Operating Instructions. The MFD supports displaying up to two databoxes with an application (ex. Chart, Fishfinder, Radar, Weather, etc.) page/pane. Within the application being viewed use the following command sequence:
1. Select MENU->PRESENTATION->OVERLAYS->DATABOXES->DATABOX 1 (or Databox 2)->ON.
2. Select MENU->PRESENTATION->OVERLAYS->DATABOXES->SELECT DATA (menu option beneath Databox 1 or Databox 2)->SPEED->SPEED

The procedures below specifies how to customize the Databar to display the Water Temp data item:
1. Select HOME->CUSTOMIZE->DATABAR SET-UP->EDIT DATABAR
2. Select the Databar cell to be modified
3. Select SPEED->SPEED from the Select Data menu

Should your system not be equipped with a Speed (through water) sensing transducer and should you desire to display SOG, then substitute "GPS->SOG" for "SPEED->SPEED" within the procedures specified above. Similarly, these databoxes may be populated with Ground Log, Ground Trip 1-4, Log, or Trip data items.

RAYFAQ#