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Practical Use of ASCAT Winds in Weather Routing
ASCAT winds are satellite scatterometer measurements of wind speed and direction on the surface of the ocean and other large bodies of water, normalized to a 10 m height. The data resolution is 25 km,...
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Viewing ASCAT Wind Measurements in OpenCPN
This article outlines the value of ASCAT wind data, and shows how work we have done at Starpath to make these files available on Google Earth can be transcribed to the format needed to be viewed in...
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Loading Surface Analysis Graphic Maps into qtVlm
After spending some time trying to build a KML file that would reproduce OPC graphic maps in qtVlm, I have had to give up for a while on this. We used it successfully for the small (~150 nmi square)...
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Measure the Eye Relieve of a Sextant Scope
The question came up today of the eye relief of the 7 x 35 monocular we sell for taking sun sights with more precision—it is also valuable for more accurate index correction measurements. Eye relief is...
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Reducing Station Pressure to Sea level pressure
The following is taken from The Barometer Handbook By David Burch. All references are to that text.Recalling that the vertical rate of pressure change is always thousands of times higher than the...
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Great Circle Distance — The Three Options
The great circle (GC) route is the shortest distance between two points on the globe, so we must always keep it in mind when planning an ocean crossing, even if we do not end up following that route....
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How to Remember the Equation of Time
On Valentine’s Day, February 14, the sun is late on the meridian by 14 minutes (LAN at 1214); three months later, it is early by 4 minutes (LAN at 1156). On Halloween, October 31, the sun is early on...
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Special Uses of the Star Finder and Sight Reduction Tables
The 2102-D Star Finder is essentially a hand-held planetarium designed for mariners to assist with celestial navigation. It can be used to plan the best sights as well as its main function which is to...
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A New Revolution in Barometers
We have worked for many years promoting the use of accurate pressure in marine navigation, which had literally fallen out of all standard texts on marine weather twenty years ago. The word "barometer"...
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Role of the Safety Depth in ENC Display
When viewing an official electronic navigational chart (ENC), the user selects three depth contours (shallow, safety, and deep) and also sets one specific depth value called the safety depth. These...
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Choosing the Best Sextant Sights
The criteria for choosing best sights is outlined in the Star Finder Book and in the manual to the StarPilot programs, but this online course has shown us that we need more specific notes on this....
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Japan Weather — A Sample of What We Can Do For All Global Waters
We had an excellent question come up in class asking simply what are the best weather resources for the waters of Japan? In our textbook (Modern Marine Weather) and in our training and resources app...
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The World Sees Atmospheric Pressure at Work
This week is the 30th anniversary of the opening of the EuroTunnel (Chunnel) between England and France. The BBC commemorated the event with a story about the first underground meeting of the tunnels...
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Landmark Labels on ENC
We are one of the first in line to lament the poor coverage of terrestrial charting in electronic navigational charts (ENC) compared to the paper chart coverage we are used to. And for good reason: we...
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Nautical Chart Carriage Requirements When Traditional Paper Charts No Longer...
Traditional paper charts will all be gone in six months; most are gone now. Here is a summary of the USCG's official chart carriage policy, followed by a short background, some details, and direct...
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Wake Low Winds: When you thought the worst was over!
By David WilkinsonStarpath InstructorStrong winds come from a variety of weather patterns. Some are large like a mid-latitude Low, some mid-size like a tropical wave, and some quite small like those...
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How to Get a Copy of a Discontinued NOAA Chart
Part 1. I know the name or number of the discontinued chart I want. (a) Go to Part 3. Part 2. I do not know what charts were available that no longer exist.(a) First we need to find out what charts...
View ArticleLearning Chart Navigation Using NOAA Custom Charts (NCC)
We are in the midst of a revolution in US nautical charting. Traditional paper charts (TPC) have been discontinued by NOAA — a process that started five years ago and is essentially completed now,...
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Wreck Symbols on Electronic Navigational Charts (ENC)
The International Hydrographic Organization (IHO) describes light symbols as the most complex electronic navigational chart (ENC) symbols in their own published standard for the symbols called IHO Pub...
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USCG License Exams Come of Age — Tide Wise
In 2020 NOAA announced that this was the last year they were going to authorize an annual set of tables for tides or for currents. The tables were called:Tide Tables2020 East Coast of North and South...
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Barometers and Marine Navigation
Even in the age of high-speed internet at sea, remarkable weather model forecasts, and satellite wind measurements, our knowledge of the correct atmospheric pressure, and how it changes with time,...
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Squall Forecasts
It is likely known that we can get GRIB formatted wind and pressure forecasts from numerical weather models such as GFS. But it is probably less known that we can get usable squall forecasts as well....
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The New Revolution in Tide and Current Predictions.
First published on OceanNavigator.com We had one tidal revolution in 2021 when NOAA announced that they were discontinuing the decades-long use of Table 2 lists of secondary station corrections, and...
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Predicting Tidal Currents in the Swinomish Channel
Historically there have been no NOAA predictions for the tidal current speed in the Swinomish Channel flowing past La Conner, WA, but local mariners know it can be strong—over 2 kts at times.Years ago...
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Digital Soundings and Water Depths from OFS Forecasts
The Operational Forecast System (OFS) model forecasts tide height and tidal currents for 15 locations around the country — a true revolution in modern marine navigation.What is probably less known, is...
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