Use this sailing calculation as a planning or educational cross-check for navigation, wind and current, rig loads, stability, anchoring, tides, visibility, performance, or recovery under explicitly stated conditions.

Own antenna height (ft)

Height of the own vessel AIS antenna above the sea surface.

Target antenna height (ft)

Height of the target vessel AIS antenna above the sea surface.

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. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Detection range (NM)

Approximate detection range between the two antennas.

• Actual conditions change with vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, regulations, and safety margins. Simplified formulas do not replace seamanship, approved stability data, or current navigation information.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Cross-check official charts, tide and weather services, instrument data, vessel manuals, and collision regulations; maintain conservative margins and a safe alternative plan.

• Lighthouse Geographic Range Calculator

  Compute the geographic range at which a light becomes visible as one point one seven times the sum of the square roots of observer and object heights in feet.

• SART Detection Range

  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.

• 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.