CPA/TCPA Risk Calculator
Compute closest point of approach and time to CPA with risk banding.
Enhanced Category
Marine & Navigation Tools
Marine navigation calculators for passage planning, closest-point checks, under-keel clearance, tide windows, route distance, set and drift, fuel range, anchoring, COLREGs training, and vessel manoeuvring estimates.
Start with these tools
Use this collection as a practical starting point for marine planning calculations, then verify consequential decisions with official charts, tide/current sources, weather, vessel data, local notices, pilotage guidance, COLREGs, and bridge procedures. For a step-by-step workflow, start with the Marine Navigation Calculators toolkit.
Anchor Scope & Holding Calculator
Check required scope and estimate holding confidence for anchoring setup.
COLREGs Encounter Classifier
Classify head-on, crossing, or overtaking geometry from bearing/course data.
Drift Estimator
Estimate set-and-drift impact on course over ground and offset.
ETA Current/Wind Compensation Calculator
Estimate ETA delay from current and wind speed penalties.
Fuel Endurance + Reserve Calculator
Calculate endurance and range after applying reserve fuel policy.
Choose by navigation task
Collision risk and relative motion
Use these tools when another vessel, encounter geometry, or close-quarters situation needs structured review.
Tide and depth planning
Use these before draft-limited entries, bar crossings, channel transits, and shallow-water approaches.
Route and distance planning
Use these to turn positions, speed, and fuel assumptions into passage-planning numbers.
Great Circle vs Rhumb Line Calculator
Best for comparing shortest-path and constant-bearing route geometry.
ETA Current/Wind Compensation Calculator
Best for adjusting ETA when current and wind reduce effective speed.
Fuel Endurance + Reserve Calculator
Best for checking endurance and range after reserve fuel is excluded.
Set, drift, and current
Use these when current, leeway, or wind drift can move the vessel away from the intended track.
Manoeuvring and vessel handling
Use these for briefing scale, margins, and setup checks before relying on vessel-specific data.
Common workflow
- Start with route distance, vessel speed, timing, and position assumptions.
- Check tide windows, under-keel clearance, fuel reserve, and environmental effects before committing to an arrival plan.
- Use encounter and manoeuvring tools when traffic, crossing geometry, restricted water, or vessel handling margins matter.
- Verify every consequential result against charts, instruments, rules, bridge procedures, and current local information.
Related collections
Full Marine & Navigation tool list
CPA/TCPA Risk Calculator
Compute closest point of approach and time to CPA with risk banding.
Anchor Scope & Holding Calculator
Check required scope and estimate holding confidence for anchoring setup.
COLREGs Encounter Classifier
Classify head-on, crossing, or overtaking geometry from bearing/course data.
Drift Estimator
Estimate set-and-drift impact on course over ground and offset.
ETA Current/Wind Compensation Calculator
Estimate ETA delay from current and wind speed penalties.
Fuel Endurance + Reserve Calculator
Calculate endurance and range after applying reserve fuel policy.
Great Circle vs Rhumb Line Calculator
Compare great-circle and rhumb-line distance, bearing, and ETA.
Tide Window Planner
Estimate passable tidal windows around high tide for draft-limited transits.
Turning Circle / Advance / Transfer Estimator
Estimate turning radius, tactical diameter, advance, and transfer.
Under Keel Clearance Calculator
Assess UKC using depth, tide, squat, wave allowance, and safety margin.
FAQ
Can these tools be used for live navigation?
They are planning aids only. Live navigation requires official charts, instruments, watchkeeping, weather, tide/current data, local rules, and bridge judgment.
Why combine tide, fuel, route, and encounter tools?
A passage can fail on any one of those constraints. Checking them together gives a more realistic plan than distance alone.
What should I verify outside ToolPatch?
Verify chart datum, tide/current predictions, weather, vessel performance, safety margins, local notices, and regulatory requirements.
How many tools are in this collection?
This category currently includes 10 focused tools, with the most practical starting points shown first.