A JURY have been told how a laser scanner was used to investigate inside the Gleision mine after the tragedy where four colliers died.
Adam Anthony, a geologist with an engineering company called Hydrock, described going into the mine and using a laser scanner to record measurements.
He said that at one stage mine inspectors had to place the scanner inside the working stall because they said the area was too unstable for him to enter.
Maps and pictures which were produced by him have been used by the prosecution to present their case to the jury at Swansea Crown Court.
The four men died when 650,000 gallons of water rushed into the mine from old workings.
The prosecution say the mine manager, Malcolm Fyfield, aged 58 from Caerhenllys, and mine owner MNS Mining Ltd, should have known that water was there. Both deny manslaughter.
One picture showed a timber pole -used to support the roof - near where the men were working on September 15, 2011, which had a water mark part of the way up it.
That had allowed him to calculate the size of the area which the water would have filled after the in-rush. He said that area would have occupied 3,154 square metres.
He also said the maximum area of space where the water could have come from was 3,786 square metres.
Mr Anthony also detailed measurements he had taken and said the breach hole - where the water rushed through - was 2.1m wide. The stall, which was 56m long, was between 7.1m and 9.1m wide.
During cross-examination by the company’s barrister, Prashant Popat QC, Mr Anthony was asked about the scope of his survey.
He said only limited areas in the mine were examined and that no other roadways - known as stalls - off the main drift were examined, neither were water sources or routes which water could have taken.
The jury also heard from Darren Bryant from the Coal Authority.
He was called to examine a depression of the ground which was discovered on farm land above the Gleision Colliery by rescuers.
He said such depressions are common and are caused when the extraction of coal underground, leaves a void.
The trial continues.