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Configure and display water depth

BoatKit keeps the depth and offset reported by each sounder, then derives three explicit measurements for displays and integrations:

  • Below waterline is the full water depth. This is the default for gauges and for outputs that support only one depth number.
  • Below sensor is the adjusted distance from the transducer to the bottom.
  • Below keel is the water depth beneath the vessel’s configured keel.

Review these values after installing a sounder, changing its internal offset, or seeing a depth that appears to be counted twice.

Review the sounder calculation​

  1. Open Settings > Vessel & Data > Sensors.
  2. Expand Water Depth and open the physical sounder’s settings.
  3. Under Calculated/Adjusted Data, compare Sensor depth and Sensor offset with Adjusted depth and Adjusted offset. BoatKit shows the adjusted pair only when it differs from the reported pair.
  4. Check Depth below waterline, Depth below sensor, and Depth below keel against the installation and current conditions.

All values use your selected length unit. Sensor depth and Sensor offset are the incoming values; the three “below” values are what BoatKit derives after applying the settings below.

Understand the calculated offset​

A positive sounder offset normally means the distance from the waterline down to the transducer. A negative offset normally means the distance from the transducer down to the keel. For a negative offset, BoatKit combines the sounder value with the configured vessel draft to calculate the transducer’s depth below the waterline.

For example, a vessel with an 8 ft draft and a sounder reporting a -2 ft keel-relative offset produces an adjusted 6 ft waterline-to-transducer offset.

If the reported offset or the vessel geometry is not usable, select Override sensor offset and enter the actual positive distance from the waterline down to the transducer. The override cannot be deeper than the configured vessel draft; if it should be, correct Draft in Vessel Info settings first. Clearing the checkbox returns to the reported/calculated offset.

Correct a sounder that applies its own offset​

Some sounders apply their configured offset to the depth value before transmitting it. Select Subtract offset from reported sensor depth for those devices. The calculated values above update immediately as you edit the override and checkbox, before you save.

For example, a sounder may transmit 42 ft of depth and a 5 ft offset even though the bottom is 37 ft below its sensor. With this option enabled, BoatKit removes the 5 ft from the reported depth, keeps the 5 ft adjusted offset, and derives:

  • 37 ft below sensor
  • 42 ft below waterline
  • 34 ft below an 8 ft draft keel

Leave the option clear when the sounder reports the ordinary transducer-to-bottom measurement. Enabling it for an ordinary sounder will understate the below-sensor value.

Choose the reference on a gauge​

When a dashboard gauge uses Depth, its settings include Depth reference. Choose Below waterline, Below keel, or Below sensor. New and existing gauges default to Below waterline. The gauge keeps Depth as its main label and shows the selected “below …” reference beside it.

BoatKit also uses below-waterline depth for single-value external outputs. When an output protocol can carry both depth and offset, BoatKit sends the adjusted below-sensor depth and adjusted transducer offset so the receiving system can reconstruct the same full water depth.

The Draft under Vessel Info must be accurate for below-keel depth and for calculating a waterline offset from a negative keel-relative sounder offset. Anchoring has separate Anchor Rode Exit Height Above Waterline and Bow Sprit Height Above Waterline settings; neither replaces the sounder’s per-sensor offset configuration.