Methods

Lumen Survey works the margins that official charts pass over — inshore shoals, tidal creeks and the unmarked hazards that matter to small boats. This page records how the work is done.

Instruments

Echo sounder

A dual-frequency transducer mounted on a survey dinghy; logged at 5 Hz and corrected for vessel speed.

GNSS

Differential GNSS for horizontal position; accuracy typically 0.3–0.8 m over the surveys we run.

Tide gauge

Pressure logger anchored at a fixed benchmark; readings reduce all soundings to chart datum.

Sketch rod

For the shallow margin where the boat can't reach, we wade and mark by rod and tape.

Reference datum

All depths reduced to Lowest Astronomical Tide. Heights of drying features given above LAT. We note the date, state of tide and reference benchmark on every survey sheet.

Tide windows

Most surveys need two to three tide cycles. We plan for neap tides when we want the shallow margin exposed; spring ebb for harbour-mouth depths. Work sometimes waits weeks for the right window.

How notes reach the Atlas

Corrections and new soundings go to Lumen Atlas as annotated sketch charts. Lumen Press pulls them into the next issue as fold-out inserts. The cycle from survey to print is usually one to two seasons.

Commissions

Harbour plans and mooring-area sketches by arrangement. We work slowly and do not take more than two or three commission jobs per season. Enquiries: survey@harbor-lumen.com.