Mapping the planet's ups and downs

Image caption Maryhill in Glasgow has never looked quite as spectacular as this 3D model

Scotland is on the rise. Well, most of it.

Freed from the colossal weight of the ice sheets which covered the country during the last Ice Age, Scotland has slowly risen. It has taken tens of thousands of years and is one of the reasons you can find seashells at the top of cliffs.

But everything is relative. More recent events have been causing parts of Scotland to sink.

The work of miners, from medieval monks to the shock troops of the Industrial Revolution and beyond, has undermined scores of communities.

A quick look at the website of the UK's Department of Energy and Climate Change reveals a long list of cities, towns and villages where old mine workings have the potential to bring a sinking feeling to the property market.

Many techniques already exist which try to map changes to the Earth's surface. Indeed geodesy - the science dealing with the measurement and representation of the Earth - is claimed by its proponents to be the oldest discipline of the lot.

Now a team of Glasgow University geographers is developing ways of looking at far bigger areas - and in much finer detail - than previous generations could have hoped for.

Radar sweeps

Led by Dr Zhenhong Li at the School of Geographical and Earth Sciences, they are looking at the surface of our planet from a high vantage point: orbit.

Every day, satellites from several nations sweep our planet with synthetic aperture radar. It is a process which allows extremely detailed information to be gathered.

That feeds into a technique known as interferometric synthetic aperture radar (InSAR), to which the Glasgow scientists apply their own modelling and mapping strategies.

Image caption Researchers in Glasgow can spot landslips near China's Yangtze river

It is complex but PhD student Andrew Singleton makes it sound straightforward. He explained: "We take one radar image taken at a certain time, and then a few days later we take a second radar image.

"And between those two time periods we can detect elevation changes in the Earth's surface.

"Obviously that has many applications for earthquakes and volcanoes. But my particular project focuses on landslide movements."

He shows me a detailed three-dimensional computer model of the banks of the Yangtze river.

Two brightly coloured areas reveal two huge landslips are sliding down and out towards the water, with the capacity to cause enormous damage over time.

On the ground the full extent may be masked by vegetation. But from orbit InSAR lays it bare, and the Glasgow team's modelling techniques mean the Chinese authorities can be forewarned.


Dr Li has applied the techniques to one of the unexpected side effects of a growing Chinese economy: subsidence. He has measured the effects of coal mining, and of the unchecked extraction of groundwater.

That has seen the water table fall by as much as three metres (10ft) in some parts of north-eastern China - and some buildings fall into sinkholes.

He has also been able to quickly assess the effects of natural disasters like the Yushu earthquake which killed thousands of people in north-western China in 2010.

Within hours of receiving radar data from the disaster area he was able to map the extent of the rupture in the Earth's surface.

"It only took me - a single researcher - two hours to produce these in the office," he says. "But it took our Chinese colleagues two weeks in the field to collect all the measurements."

And when they did that work on the ground, they found Dr Li's measurements from orbit had been accurate to within 10cm.

It is hoped one day the techniques could be used not just to assess the damage caused by earthquakes and volcanoes - but to give advance warning of where and when they will occur.

Dr Li has also established how old America's Sierra Nevada mountains are - by showing how quickly they're rising.

And another of his PhD students is looking at how Sumatran peat bogs are sinking to show for the first time how burning, draining and farming them may be affecting climate change.

The team do not just confine themselves to orbit.

High flats and supermarkets

Another doctoral candidate, Haval Sadeq, is using stereoscopic photos taken from aircraft to build a 3D computer model of a section of northern Glasgow.

As he spins and tilts it on the screen it is easy to make out Maryhill Road, the high flats, the local Tesco - even the cars in the supermarket car park.

It is a fair bet this particular part of Maryhill has never before looked quite so spectacular.

Haval says potential applications of the technique include town, transport and airport planning.

In another development, a PhD scholarship is on offer for an investigation into whether Scotland really is still springing back after the ice cap melted.

The successful candidate will use InSAR and the Global Positioning System to find out if things have settled down at last.

Which brings us, in a roundabout sort of way, back to those old mine workings. Glasgow's ever-fashionable West End is not immune to them.

Dr Li's modelling has established that his own office - and the entire university campus - is quietly sinking, by between seven and eight millimetres a year.

It is great science. But what is it going to do to property prices?