David Burch Navigation Blog
Notes on marine navigation and weather
Wednesday, March 4, 2026
Grib Offsets for Routing in qtVlm
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When we compute the optimum sailing route in a nav app like qtVlm, we use the polar diagram of the boat to provide its performance expectati...
Saturday, January 10, 2026
Access Historic OSCAR Currents in GRIB Format
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We have long suggested that the satellite based measurements of ocean currents called OSCAR ( Ocean Surface Current Analyses Real-time ) are...
Saturday, December 27, 2025
Evaluating wind models in 2025 Sydney-Hobart Race
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We have been following the TransPac52 fleet in the 2025 Sydney Hobart Race as a way to learn about evaluation of currents and winds and ro...
Wednesday, December 10, 2025
The Three Sets of Nautical Chart Symbols We Need to Know
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In 2025, all traditional paper charts were permanently discontinued, after which the only official NOAA nautical charts are the electronic n...
Monday, November 10, 2025
NOAA's New Nautical Chart Numbering System
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Official US charts with chart numbers started with the founding of the US Coast Survey in 1807 that evolved through several forms into the m...
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