RFS Inspector Ben Shepherd explains some of the variables that go into mapping a fire

During the height of the Coolagolite fire the size of the fire changed from 5800ha to 4500ha to 5200ha and the shape changed.

While the shape and size might be expected to get bigger, getting smaller might have confused some people.

But as Inspector Shepherd explained, it's all to do with the mapping and information received from various sources.

"When a fire takes off we give an outline of where it is spreading and sometimes this is a very basic shape to give people an idea," Inspector Shepherd said.

The initial 'burnt area' is often determined using situation reports provided by firefighters on the ground and is a rough estimate of where the fire has travelled.

But then the RFS receives information such as mapping, thermal imaging or line scans, from various aircraft.

When a helicopter can't go up because of weather conditions, sometimes the RFS Citation aircraft gets line scans from a thermal image.

"It's a snapshot in time. You can see spot fires and when we draw the map we include those. It's a very fluid situation but the spot fires can be a real risk and things can change very rapidly and so sometimes it is a rough map," he said.

As more information comes in, such as from firefighters on the ground, the map is updated.

"As soon as it's mapped, the public see it, we don't have a different version or hide anything," Inspector Shepherd said.

The final size of a fire is reached using a range of information collected over the course of the incident and as a result, is subject to change.

"We're trying to use the best tool at the time and using it to make operational decisions on the ground."

Spot fires can travel many kilometres ahead of the fire and can block an exit route which is why they are included in mapping. Sometimes initially they appear fairly large because information may be coming in from various sources including the public. As the size is clarified, so are the maps.

It's also one of the reasons for giving an alert to say it is too late to leave and shelter inplace.

"With spot fires around exit routes, the last thing we want is for people to get on the road," Inspector Shepherd said.

Spot fires can escalate rapidly blocking a road or bringing down trees, which is why - at that stage - the advice is to shelter in place as the fire front passes through.

It was a major consideration as the Coolagolite fire started to spot across to Cuttagee and Barragga Bay which was when people ahead of the main fire front were warned it was too late to leave.

"Fires are very, very fluid things. You can take the exact same fire and conditions at a different time and the two will burn in a different way. As soon as there's a risk to the community we give out the information."

"When we give out those warnings we want people to follow them," Inspector Shepherd said, adding that preparation was vital.

"People need to recognise that when they have prepared their own properties it can pay ultimate dividends. We've seen that in the last 48 hours."

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He said that while many chose to live in those areas because they are beautiful, there's always a risk that fire would happen.

"With a well prepared home, you've got a good chance, whether you are defending it, the RFS is or there's no one there," Inspector Shepherd said.

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"There are so many important things you need to do to prepare your property, like hazard reduction around the home and sheds, cleaning gutters, trimming overhanging branches and clearing a buffer zone around the home. It all gives you and your property the best chance.

"Make the firefighter's job easier by playing your part and giving your home the best chance," Inspector Shepherd said.

And if you live in a rural area, think about stepping up to volunteer at your RFS. There are many vital roles, not all of them involve being on the fireground, and being involved will help you understand fire behaviour better.

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