Friday, December 19, 2014

Grounding of the Arafenua on the Tikei atoll

Arafenua customs patrol boat on the reef

From BEA Mer

During a surveillance mission, the Arafenua customs patrol boat set sail from the island of Fatu Hiva (Marquesas archipelago) to Tikei atoll (Tuamotu archipelago) on 30 May 2014 at 22:00 and grounded there on 1 June at about 04:00 (14°56’,504 S et 144°32’,436 W on the North coast of Tikei)

 Tikei with SHOM nautical chart correctly shifted on the the GeoGarage platform

Tikei is a small coral island 2 miles long, wooded, without lagoon, uninhabited and unmarked, from northern Tuamotu in French Polynesia.
It is 345 miles from the port of Papeete in Tahiti.
It is difficult to land there because the island is surrounded on all sides by a reef which consists of a first barrier at the surface of water then a platier covered with 20 cm of water.
The tidal range is very low, about 30 cm.
The 1000 metre probe line is located approximately 0.6 miles from the reef.

Before leaving Fatu Hiva on Friday 30 May, the captain overboard gathered part of the crew to explain the mission.
At the end, it traces the road on the MaxSea PC installed in 2012 which is connected to a GPS and a Furuno radar.
Starting outside Fatu Hiva's Bay of Virgins, the road tangents the 1,000 metre sounding line in northwest Tikei.

The vessel sailed on a dark night to an uninhabited islet without any light source, making optical detection impossible.
Furthermore, overcast weather with squalls increases the watchman's difficulties and reduces the quality of the radar watch.
Other weather conditions (wind and swell) have no influence on the circumstances of the occurrence.
During the day, the optical watch would have made it possible to warn the shift manager that he was on his way to the platier.
The arrival at night can therefore be considered as a determining factor.
The weather conditions on June 4 were as forecast, 1.50 to 2 m swell.
The arrival of a swell train that generated a series of waves breaking whose height was above average is the determining factor.

The patroller has an electronic mapping equipment that works with MaxSea software.
This equipment is a ECS and not an ECDIS.
This ECS is not recognised by the IMO as a replacement for the paper charts.
The electronic chart used comes from a private publisher, it is not an ENC published by an official hydrographic service.
Consequently, electronic charting equipment can only be an aid to navigation; it cannot be the primary navigation or reference system.

 Copy of map 7347 used "from the Tuamotu Archipelago to the Southern Islands".

There is no landing map of the island.
The most accurate paper chart is the "6689 - Tuamotu Islands (western part)", the one used for the approach.
It is, seen the scale (1/595 000), unusable for navigation in the direct vicinity of Tikei.
It was based on bathymetric information collected by SHOM until 1977.
It was last updated in 2010.
The geodetic reference does not appear on this map.
According the scale (1:595 000), the thickness of the pencil line (0.3 mm) is 178.5 m.
A cartridge indicates that the chart should not be used without consulting other documents, in particular Volume 1 of the Navigator's Guide for information on charts, their accuracy and limitations.
With regard to other navigation aids (radars, GPS, depth sounder), no malfunction was reported.
The lack of a landing card is an underlying factor.

The course was plotted by the captain at sea on MaxSea to arrive in the northwest of Tikéi near the 1000 m sounding line.
It is in fact an approximate isobath (broken line).
The master on board requested to plot this route on the two paper charts (7347 and 6689).
The road passes 1 mm from the islet of Tikéi on map 6689 (less than 600 m) and the landing point is not formalized although it is the first time that Arafenua approaches Tikéi.
It appears that the rules of caution set out in the navigator's guide volume 1 and its supplementary booklet entitled "L'hydrographie, les documents nautiques, leurs imperfections et leur bon usage" were not respected.
In particular the main advice for the layout of a road so as to ward off dangers which is the "thumb rule".
As specified in the above documents, the thumb refers to both an old length (2.7cm) and the width of the browser thumb.
The guard distance from the coast of Tikéi to the scale of the larger paper chart (6689) is nearly 9 miles (36 minutes at 14 knots).
Within this distance Tikéi should only be approached with great care.
The "thumb rule" also applies to electronic maps provided that the map is used at compilation scale, i.e. the scale of the paper map used to develop the electronic map.

The ease of use of the mapping software and the illusion of precision given by the electronic map that can be zoomed at will associated with GPS have made us forget the basic rules of caution.
In particular the constructive doubt with which aids to navigation should be exploited.
The habit of sailing together, for many years and in areas known for transits of a few hours, has blunted the knowledge acquired during initial training.
The master at sea's brief elaboration of the route and the absence of remarks on the route by the various watchkeepers were a determining factor in the grounding.

During the 0100 to 0400 watch, watch leader B could not accurately determine the island's position on the radar due to rain.
Having failed to adjust the anticlutter, he focuses on tracking the course on MaxSea without using the overlay function of the second radar.
He does not master the use of this equipment installed in 2012.
The island does not appear on the MaxSea map because the zoom is set to maximum.
Watch leader B loses track of the distance between him and Tikéi until he prepares his relief. Although the optical and radar watches were severely degraded, he did not take any action while approaching Tikéi at night.
It was only about 5 minutes before the grounding that he asked to intuitively reduce the engines by 100 revolutions.
The conduct of the landing watch is inadequate.
This is a determining factor.

The grounding

The ARAFENUA grounded because the actual position of the island is 1500 m further north than that indicated on the MaxSea mapping.

 DF 48 Arafenua was deemed irrecoverable after grounding on 1 June in French Polynesia.

At the scale of the 6689 paper map used, these 1500 m represent 2.5 mm.
This shift in the island's position is a contributing factor.

Extract from the Arafenua MaxSea mapping with overprinting of the satellite image where the edge of the 'platier' appears on the 2000 m probe line
Import in Google Earth of the route drawn on MaxSea  

Screenshot of 'Arapo' ECDIS, with Arafenua position and radar overlay
According to SHOM information, the Tikéi atoll was the subject of geodesy work in 1948 (astronomical geodesy) and 2001 (GPS).
These geodetic measurements are consistent with the uncertainties of the astronomical measurements: the difference is 150 m (approximate value, the precise location of the astronomical geodesy station has not been found).
The paper chart 6689 (scale 1/595000), published in 1978, was based on chart 6057 (1/510000), which it replaced.
Map 6057, published in 1952, uses one minute of topography also produced by the 1948 geodetic mission.

 original geoTIFF 6689 chart overlaid on Google Earth
- showing original 1500 meters shift with satellite imagery because datum none WGS84-
Analysis of the documents shows that this minute is not consistent with the geodetic measurements, which was not identified during the preparation of the mission documents and during the cartographic work: the position of the island on the topographic minute is 1 mile further south, probably due to a transcription error during the preparation of this document.
This shift affected the chart 6057 then the current chart 6689, as well as the electronic navigation chart ENC FR266890 which were elaborated from this same paper chart.

6689 Iles Tuamotu (partie Ouest), de Tahiti à Rangiroa et Makemo
scale : 1:593,700 / pub 1978 / ed 2009/ datum : unknown -non WGS84-

  view in W4D (Android test)

ENC FR266890 (ed : 30/11/2010) scale 1:350,000
Polynésie Française - Iles Tuamotu (Western part)

The force of habit and the absence of constructive doubt in the use of navigational aids combined with a lack of vigilance in the development and monitoring of navigation led to the grounding.
Note : SHOM issued offset information for paper map 6689 "Tuamotu Islands (western part)" (Preliminary Notice 14 37-P-07), and associated ENC FR266890.

Other notes from BEA mer :
  • To the software publisher MaxSea :
3 2014-R-028 : to display on the vector map a blatant warning when the user uses the zoom beyond the compilation scale.
  • At SHOM :
4 2014-R-029: to propose to IHO an amendment to the standard to show on ENC maps a clear warning when the user uses the zoom beyond the compilation scale.

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