Nov 072014
 
capblanche

Looking out of the window was not really an option for the pilot conducting the 28, 372 GRT containership Cap Blanche on the Fraser River, British Columbia, Canada, on 25 January this year. With fog reducing visibility to 150 metres he could not even see the bow of the 221.62 LOA vessel, but he did have his trusty portable pilotage unit, PPU, which he relied upon exclusively for navigation and connected it to the vessel’s AIS. But the AIS had a secret, one which put Cape Blanche on the silt at the river’s Steveston Bend.

The accident report from Canada’s Transport Safety Board brings to light a little known aspect of navigation by GPS yet one that might not have led to the grounding had the pilot not been essentially left to his own devices even when his actions conflicted with the vessel passage plan.

The PPU had a predictor function that projects the vessel’s future position by performing geometric calculations based on the vessel’s current rate of turn, position, heading, course over ground, COG, and speed over the ground, SOG. The COG and SOG are derived from GPS values that continuously fluctuate, even when the vessel maintains constant speed and course due to inherent errors and inaccuracies in the GPS. To stabilize these values, a GPS smooths these inputs to provides the user with a more stable COG and SOG.

One can often see the GPS fluctuations on a GPS-equipped tablet computer or smartphone.

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Jan 192013
 

 

USS Guardian - thought the reef was eight nautical miles away

USS Guardian – thought the reef was eight nautical miles away

With a US Navy investigation underway to assess the circumstances surrounding the USS Guardian grounding that occurred in Philippine waters at 02.25 on 17 January local time there are lessons already to be learned: Charts are not infallible even if they are on screen and it is not wise to navigate to fine tolerances with the aid of GPS when the underlying data is less accurate than the GPS.

An inaccurate chart is not a defence – not bumping into bits of ground remains the master’s responsibility.

Much of the Philippine waters have not be surveyed for 50 years or more, an issue highlighted when the Greenpeace ship Rainbow Warrior also grounded on Tubbataha Reef in 2005. The chart in use showed the reef 1.5 miles from where it actually was.

The digital chart aboard USS Guardian, an Avenger-class mine countermeasures vessel, showed a position about eight nautical miles in error. At the time of the grounding the vessel was attempting passage through a channel just half that width.

Many Philippine charts have not been re-surveyed in some 80 years. Transferring this aged data to an electronic chart does not increase its accuracy. The current NGA chart for Tubbataha reef appears to be the 1986 edition, based on Philippine charts of 1975 and earlier.

According to a source in the Philippine Coastguard “With the 1940 or 42 charts by NAMRIA, there might really be a problem with  that’s why we are advised to at least have a difference of Three nautical miles from the shoreline, we have to assume that there is one nautical miles changes in the chart already”.

NAMRIA tells Maritime Accident Casebook that the last hydrographic and topographic survey covering Tubbataha Reef was conducted in 2006 using single beam echosounder for the hydrographic data, 2008 is the latest hydrographic survey using multibeam echosounders. The chart was first published last May 2009 and the reef is marked as a restricted area on current charts.

On Friday, 18 January, the US National Geospatial-Intelligence Agency, NGA provided the US Navy with preliminary findings of a review on Digital Nautical Charts (DNC) that contain inaccurate navigation data and may have been a factor in the Guardian grounding.

This followed the realisation by NGA that there might be a potential inaccuracy regarding the Tubbataha Reef digital chart. NGA has reviewed data from more than 150,000 square nautical miles in the surrounding area and found no additional errors.

The incident may also lead to a review of the $30m 2006 joint hydrographic survey agreement between the US Navy and the Philippines after nine years of negotiations. The project was to use advanced sonar technology to map shipping lanes, harbors, and ports throughout the Philippines. However an incident involving a Philippine Maritime Police Patrol vessel firing warning shots against a US Navy survey vessel in January 2008 led to US Navy surveys being restricted to within four nautical miles of the coast.

The project was expected to generate some $300m in commercial value.

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Feb 232012
 

After the Tricolor sank following a collision two other vessels rammed the wreck. A foretaste of what GPS jamming might cause?

When, rather than if, the English Channel sees a major maritime catastrophe due to jamming of GPS signals it will not be for lack of warnings (See more below). The latest came during a conference at the UK’s National Physical Laboratory on 22 February.

MAC has previously reported on the threat to ships created by GPS jamming equipment now easily available on the internet. That threat is now a clear and present danger according to Bob Cockshott, Director of Position, Navigation and Timing at the ICT Knowledge Transfer Network, and organiser of the conference.

Warns Cockshott: “With the reliance on GPS systems in the maritime environment, highlighted by the General Lighthouse Authority, our vulnerability on land and at sea should not be underestimated. As well as immediate concerns, this conference has laid out the next generation of threats, in the form of spoofing and time sabotage – deliberately misleading users for criminal purposes rather than simply denying service. We must ensure that alongside dealing with the threat posed by jamming, we also stay ahead of advances in the criminal world.”

Global position satellites generate very weak signals which are easily swamped by cheap jamming equipment. The equipment is legal to own but illegal to use. Research by the Sentinel project showed a disturbingly wide use of such jamming equipment, including exploitation by criminals. Continue reading »