The team have to use ropes which are between 100m and 200m long
Scotland's big trees are being scaled by experts looking to confirm the identity of the UK's tallest tree.
A team of arboriculturists climbed the Douglas Fir near Dunans Castle, Argyll, on Thursday and were working at the Hermitage, near Dunkeld, in Perthshire.
Next they will head to the Grand Fir in Diana's Grove at nearby Blair Castle.
Along with gathering official measurements for the Tree Register, the team wants to highlight the great forests available in Scotland.
Mark Tansley from Sparsholt College in Hampshire told the BBC Scotland news website that climbing tall trees could be a difficult task.
"You need a huge amount of equipment," he said.
"You need a lot longer ropes than we would normally use in arboriculture. We've got ropes ranging from 100m to 200m.
"To get a line in we use a giant catapult to fire a bean bag with a thin line attached to it into the canopy of the tree, that we will then tie our climbing ropes to.
"That can be quite a challenge sometime - it took us about three hours to get the line into the tree yesterday but it's good fun.
It's great for people to get out and enjoy them even if it's just from ground level
"It's a great career path, it's quite an office to have - being 100ft up a tree."
And Mr Tansley said their work in Scotland was about more than just gathering facts and figures - it is about trying to get people into forests to have a look.
"It's about looking at the tree as a species and really trying to find the tree's limit - how tall will they grow and the volume of the trees - they're just absolutely incredible plants," he said.
"I'm stood at the base of one now and it's absolutely mind-bogglingly large and there are loads of trees out there like this.
"It's great for people to get out and enjoy them even if it's just from ground level.
"They're fantastic resources and I don't think we appreciate them enough, I think we take them for granted sometimes."