Use this sailing calculation for planning or education when the vessel, units, reference directions, environmental conditions, and assumptions are explicitly known.

SART height (ft)

Required number in ft. Mounting height of the SART above the water in feet.

Responder antenna height (ft)

Required number in ft. Antenna height of the responding vessel above the water in feet.

The cited overview of Maritime safety supplies background for the terminology and domain context used by this tool.^[1]

Estimate the radar detection range of a search and rescue radar transponder as one point one seven times the sum of the square roots of the SART mounting height and the responding antenna height in feet, capped at forty nautical miles. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Detection range (NM)

Returned number in NM. Expected radar detection range of the SART.

• Vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, and safety margins can make real conditions differ from a simplified result.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Cross-check current charts, tide and weather services, instrument data, vessel manuals, and applicable navigation rules, and retain a conservative alternative plan.

• AIS Range Estimate

  Estimate the range at which an automatic identification system target is received as one point one seven times the sum of the square roots of the own and target antenna heights in feet.

• VHF Range Calculator

  Estimate very high frequency radio range over water as one point one seven times the sum of the square roots of the vessel and shore antenna heights in feet.

• Horizon Range Calculator

  Compute the distance to the visible horizon in nautical miles as one point one seven times the square root of the observer height in feet.