Thursday, September 24, 2020

GPS Interference

From MARAD

 The equipment shows the ship’s position is on land, instead of the actual position 25 nautical miles offshore.

1. Reference: None.
This revised advisory cancels U.S. Maritime Advisory 2020-007

2. Issue: Multiple instances of significant GPS interference have been reported worldwide in the maritime domain.
This interference is resulting in lost or inaccurate GPS signals affecting bridge navigation, GPS-based timing, and communications equipment.
Satellite communications equipment may also be impacted. Over the last year, areas from which multiple instances have been reported include the eastern and central Mediterranean Sea, the Persian Gulf, and multiple Chinese ports.
The U.S. Transportation Command “Message for Industry” at https://go.usa.gov/xdSpq provides additional GPS interference information.

3. Guidance: Exercise caution when operating underway and prior to getting underway.
The U.S. Coast Guard Navigation Center (NAVCEN) and NATO Shipping Center websites contain information regarding effective navigation practices for vessels experiencing GPS disruption.
The information reaffirms safe navigation practices when experiencing GPS disruptions, provides useful details on reporting disruptions, and is intended to generate further discussion within the maritime community about other disruption mitigation practices and procedures.
This guidance also recommends reporting such incidents in real time; noting critical information such as the location (latitude/longitude), date, time, and duration of the outage/disruption; and providing photographs or screen shots of equipment failures experienced to facilitate analysis.
The NAVCEN information is available at: https://go.usa.gov/xQBaU.

4. Contact Information: Maritime GPS disruptions or anomalies should be reported immediately to the NAVCEN at https://go.usa.gov/xQBaw or via phone at 703-313-5900, 24-hours a day.
NAVCEN will further disseminate reported instances of GPS interference in this region to the NATO Shipping Center.

5. Cancellation: This message will automatically expire on March 21, 2021.

For more information about U.S. Maritime Alerts and Advisories, including subscription details, please visit http://www.marad.dot.gov/MSCI.

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WMO verifies -69.6°C Greenland temperature as Northern hemisphere record


From Royal Meteoroly Society

Climate detectives uncover 30-year-old temperature reading

In an article released online today (Wednesday 23 September, 2020) in our Quarterly Journal, the World Meteorological Organization has recognised a temperature of -69.6°C (-93.3°F) at an automatic weather station in Greenland on 22 December 1991 as the coldest ever recorded in the Northern Hemisphere.

The temperature record was uncovered after nearly 30 years by “climate detectives” with the WMO Archive of Weather and Climate Extremes.
It eclipses the value of -67.8°C recorded at the Russian sites of Verkhoyanksk (February 1892) and Oimekon (January 1933).
The world’s coldest temperature record, of -89.2°C (-128.6°F) on 21 July 1983, is held by the high-altitude Vostok weather station in Antarctica.

The WMO Archive of Weather and Climate Extremes includes records such as the world’s highest and lowest temperatures, rainfall, heaviest hailstone, longest dry period, maximum gust of wind, longest lightning flash and weather-related mortalities.


In this July 18, 2011 file photo, a boat steers slowly through floating ice, and around icebergs, all shed from the Greenland ice sheet, outside Ilulissat, Greenland. Climate historians hunting for past temperature extremes have unearthed what the U.N. weather agency calls a new record low in the Northern Hemisphere.
The World Meteorological Organizations publicly confirmed Wednesday Sept. 23, 2020, the all-time cold reading for the hemisphere: -69.6 Celsius recorded on Dec. 22, 1991 at an automatic weather station in a remote site called Klinck, not far from the highest point on the Greenland Ice Sheet
(AP Photo/Brennan Linsley, File)
 
The weather station at Verkhoyanksk, which previously held the northern hemisphere cold temperature record, hit the headlines when it recorded a temperature of 38°C on 20 June during a prolonged Siberian heatwave.
WMO is currently verifying whether this is a new record high temperature north of the Arctic Circle (a new category for the archive).
That ongoing investigation, following the lead of this evaluation, will also examine possible past occurrences of high temperatures north of the Arctic Circle.

“In the era of climate change, much attention focuses on new heat records.
This newly recognised cold record is an important reminder about the stark contrasts that exist on this planet.
It is testimony to the dedication of climate scientists and weather historians that we are now able to investigate many of these older records and secure a better global understanding of not only current, but also historical, climate extremes,” said WMO Secretary-General Professor Petteri Taalas.

While most climate extreme observations evaluated by the WMO’s Archive of Weather and Climate Extremes have been made within the last few years, occasionally climate historians uncover long overlooked weather data that contain important climate information that must be analysed and verified.
Such was the case with the just-concluded evaluation of a nearly 30-year-old weather record of an automated weather station at the remote Greenland site named Klinck, located at an elevation of 3,105 metres close to the topographic summit of the Greenland Ice Sheet.


The automatic weather station operated for two years in the early 1990s as part of a network established by the University of Wisconsin-Madison to record the meteorological conditions around the Greenland Crest during the Greenland Ice Sheet Project.
In 1994 it was returned to the laboratory for testing and then sent for use in the Antarctic.

This was before WMO began evaluating global extremes, as the World Weather and Climate Extremes archive was established in 2007.
The record came to light only after a WMO blue-ribbon international panel of polar scientists tracked down the original scientists involved.
The committee commended the station’s original project scientists in the careful maintenance of the calibrations and metadata for an observation made so long ago.
Such diligence indicates a high degree of detail and quality of observation.

After extensive analysis of the equipment, observation practices and the synoptic weather situation of December 1991, the panel unanimously recommended acceptance of the observation as valid.

“This investigation highlights the ability of today’s climate scientists to not only identify modern climate records but to play "climate detective" and uncover important past climate records - thereby creating a high-quality long-term record of climate for climate-sensitive regions of the world,” said Professor Randall Cerveny, Rapporteur of Climate and Weather Extremes for WMO.

The WMO investigations also serve to improve the quality of observations through the careful analysis of observation practices and proper equipment selection.

All components of the Automatic Weather Station had to be selected to be able to function in extremely cold conditions, according to George Weidner, who helped design the station.

“On Greenland, all of the sites were installed by snowmobile.
So the Automatic Weather Station had to be packed to survive a traverse over very rough snow surfaces.
Years of packing experience in Antarctica helped us keep our Automatic Weather Station safe and snug on the sleds being pulled by the snowmobiles,”he said.
A.
Unaltered Klinck AWS photograph as photographed in 1994 during a maintenance check.
Photograph by Mark Seefeldt.
B.
Annotated 1990 Klinck AWS installation photograph: a) air temperature probe at 3.3 metres after installation, b) 2.0 – 2.2 metres above snow surface (at time of time of 22 Dec.
1991 -69.6°C temperature observation), c) estimated snow level in July 1992, d) estimated snow level at time of 22 Dec. 1991 -69.6°C temperature observation, and d) lower temperature probe installed at ~0.9 metre above snow surface at installation (became buried in September 1991, based on the AWS data).
Photograph by Dr. Julie Palais

The WMO international evaluation committee consisted of polar science and climate experts from Denmark, Spain, the United Kingdom and the United States.

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Wednesday, September 23, 2020

France & misc. (SHOM) layer update in the GeoGarage platform

166 nautical raster charts updated & 3 charts replaced & 1 new chart added

Tuesday, September 22, 2020

Autumn equinox

Today is the autumn equinox.
Perfect symmetry between the 2 hemispheres that receive the same amount of solar energy over a day with 12 hours of day/12 hours of night.
Can you see the sun's track exactly on the equator in this satellite animation?

This year's Autumnal Equinox falls on 22 September at 14:30 BST.
The equinox is when the centre of the Sun (as viewed from Earth) crosses the Earth's equator.

Curiosities at the chart makers Imray


The protractor engraved with William Heather's name which was probably his personal instrument

From Yachting Monthly by Katy Stickland

Katy Stickland goes behind the scenes at Imray and discovers the treasures held by the nautical publisher

‘Great Andaman where Inhabitants are said to be Cannibals’.
These ominous words hang in the air, which is thick with the smell of old paper, ink and dust as we gingerly leaf through piles of ‘blueback’ charts in the basement of Imray, Laurie, Norie and Wilson Ltd.

Yachting Monthly is being given a tour of the nautical publisher’s HQ in Wych House in St Ives, Cambridgeshire.

We are poring over some of the company’s oldest charts including this one from 1784 of Andaman and the Nicobar Islands in the Indian Ocean.

The chart is marked in black and red ink, with everything in red highlighting an amendment.

A 1784 chart of the Andaman Islands with amendments in red ink. Credit: Katy Stickland

It also includes remarks from one Captain Phineas Hunt, detailing the Nicobar Islands’ channels and harbours as well as where there is an ‘abundance of Hogs & Fowls’, vital information for Merchant Navy ship captains in the 18th and 19th centuries.

Although Imray as it is today was incorporated in 1904, the roots of the three chart publishers that formed it – James Imray & Son, Norie & Wilson and RH Laurie – can be traced back to the mid 1700s.

For centuries these London-based firms, along with a few other companies, were responsible for producing what became known as blueback charts because of the distinct blue manila paper which was used to back them.

This not only strengthened but also distinguished them from the British Admiralty charts, which were published on heavier-weight paper.

These privately printed charts were mainly used by the Merchant Navy; publications for recreational sailors only really became available from the 1890s.

Imray director Lucy Wilsons shows YM some of the firm’s old blueback charts.
Credit: Theo Stocker

By then, competition from Admiralty charts was damaging the traditional private chart trade, a threat that would eventually lead to the amalgamation of the three firms.

It was Norie & Wilson which took the prudent step in publishing Fore and Aft Seamanship for Yachtsmen: With Names of Ropes, Sails, and Spars in a Cutter, Yawl, or Schooner in 1878.

But it wasn’t until after the First World War that recreational sailing started to become the focus of Imray’s business, partly because of the growth of yachting in the UK.

The C and Y series charts were launched in the late 1920s.

Opposite Wych House’s basement are a framed 1962 C4 chart of the Needles Channel to Portland, and a 1947 chart of the London Docks and the River Thames.

Decades later, the yellow and green colouring on the C4 is still almost psychedelic, competing for eye gaze with the vibrant reds and greens used for colouring the London chart.

Some of the early charts feature the routes of ships

The C4 also has some of the same features of the original bluebacks.

Within the chart are smaller charts for Weymouth Harbour, Christchurch and Lulworth Cove.

The addition of large scale harbour plans were always considered good value for money by Merchant seamen, as it meant they didn’t have to buy additional charts, a continuation which was warmly welcomed by recreational sailors.

Today, Imray C charts cover the whole of the British Isles and parts of Europe.

Imray also rewrote some of its pilot books to include anchorages and passages accessible by smaller sailing boats.

Imray still retains the ethos of its founders: to produce charts using accurate hydrographic data

Previously, pilot books had just concentrated on the needs of larger ships.

The Pilot’s Guide to the English Channel and The Pilot’s Guide to the Thames Estuary and the Norfolk Broads were both rewritten by Eric Wilson and published in 1932 and 1934.

The initial success of Imray’s foray into the yachting market was abruptly halted by the start of the Second World War, which saw Imray move its offices from London to Cambridgeshire.

St Ives was chosen because the print works Enderby & Co were based there, and it had lithographic printers large enough to print charts.

Modern and older versions of Norie’s Nautical Tables for astro navigation

Throughout the 1960s and 1970s Imray established itself as a publisher for cruising sailors.

It started producing folded charts, and in 1979 ended the lining of charts with blue manila paper.

In 1999, the first digitally drawn charts using GIS (geographic information system) software were produced.

Recently Imray has undergone another major change in its production system allowing it to develop new products such as Imray Electronic Navigation Charts (ENCs), update products more frequently, align book, chart and digital products more closely with each other and receive and manipulate data more easily.

Despite advances in technology, Imray still retains the ethos of those three original publishers: to produce charts using accurate hydrographic data.

It is appropriate our tour ends in the boardroom, where the portraits of those early founders stare down at us, alongside the tools of their trade.

The brass protractor belonging to Norie’s founder William Heather; Lord Nelson’s favourite chair which was given to Heather by a friend who served with Nelson on the HMS Boreas and the early editions of Norie’s Nautical Tables, still produced by the company.

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