Plan with the reference, not just the number.
Six practical guides for the details that change a bridge-passage plan. Read the explanation, try the tool, keep the unresolved checks visible.
How to record your boat’s real air draft
Start at the loaded waterline, finish at the highest point, and keep the buffer separate.
Read the field guide Bridge planningCharted bridge clearance vs measured air gap
A chart attribute, a sensor observation and your remaining margin are three different things.
Read the field guide Tides & referencesMLLW, MHW and the datum trap
Matching units is not enough. Heights also need a compatible vertical reference.
Read the field guide Tides & referencesWhy low tide is not a slack-current forecast
A high/low table answers a water-height question, not a current-speed question.
Read the field guide Data confidenceLive, stale or unavailable: read the data state first
A successful request is not the same thing as a current observation.
Read the field guide Passage workflowA bridge-passage checklist you can actually use
Record the evidence for each check—not just a row of reassuring ticks.
Read the field guideA field guide should lead somewhere useful.
These guides pair source definitions with worked examples and a next action. They do not reproduce a live chart, opening schedule or conditions forecast. Use the linked official source to verify information for your intended passage.
NOAA: What is air gap? ↗NOAA tidal datum definitions ↗NOAA ENC Direct to GIS limitations ↗USCG Local Notices to Mariners ↗