Human error and bridge culture issues allowed the containership Rena to strike the Astrolabe Reef in clear weather in the early hours of October 5, 2011.

The interim report into the investigation released today and available online at www.taic.org.nz shows navigation errors were not picked up and that marks were added to charts after the grounding.

This chart was released this morning in the TAIC report. It plots the ship's course in its final hours afloat. See the chart in full below.

The report sets out the facts and circumstances as established at this point.

The interim report does not contain any analysis of the facts or make any findings or recommendations.

The facts are that the Rena's last known position before she struck the reef was at 1.42am when the ship was about 20 nautical miles east-north-east of the reef.

A seaman tasked with plotting the ship's GPS position on the chart at 2am failed to do so because the captain and the second mate were leaning over the chart table discussing preparations for their arrival at Tauranga.

The position was entered in the log book, and plotted on the chart after the grounding – and at a position further north. The log book was amended to match the charted position.

The interim report also notes the second mate set up the ship's radar to show if the ship had deviated from its track, but the parallel indexing was switched off at 1.58am to remove clutter from the screen.

The parallel indexing monitors progress as the ship tracks along its course. At 1.50am the ship was heading directly towards the reef.

The investigator in charge of the Rena inquiry, Robert Thompson, says the bridge issues and "bridge culture" issues will be part of the final report.

He also says the investigation found no evidence to support allegations that the captain was involved in birthday celebrations during the voyage.

Rena's approach to Tauranga

The Rena was steered by autopilot for most of the voyage from Napier, including from midnight until the time of the grounding. The Rena's auto pilot operated off a gyro compass.

The Rena's GPS calculated the ship's ground track. GPS positions were plotted on the ship's chart at 1am and 1.20am. The two positions were marked on different charts.

The earlier one on NZ54 and the later one on the larger scale NZ541 Mayor Island to Okurei Point, chart.

Neither position was marked on both charts. No position was transferred from one chart to the other when changing charts.

The interim report notes the difference between the ship's gyro compass heading and ground track was about two degrees south of the ship's gyro heading, a difference caused by current set, leeway and compass error.

The ship's actual course was roughly parallel to and about a quarter of a nautical mile to the south of the planned passage at about 1.30am.

The vessel struck the reef at about 2.20am.

Report's release welcomed

Transport Minister Gerry Brownlee says the report's release shows 'good progress” is being made into determining the cause of the disaster.

'It establishes some verified facts that will enlighten ongoing investigations,” says Gerry.

Bay of Plenty Regional Council Chairman John Cronin welcomes today's release too.

He says it provides some clarity about how the accident occurred and feels its release was important for the Bay of Plenty community.

'Our communities have been through a lot since this accident and hopefully the information provided in this report will help our community better understand what happened and then assist them in the healing process,” says John.

'We really appreciate that this has been a difficult time and we have been very grateful for the patience and understanding of iwi and our community.

'I want to again thank all levels of government and the agencies which have been involved in the response, iwi and our community for their ongoing support and to also acknowledge the commitment and hard work of regional council staff who have dedicated many hours to helping with this incident.”

The final Transport Accident Investigation Commission's final report into the Rena's grounding is due next year.