'Smoking gun' in residents' fight against Westconnex

Thousands of households along the Westconnex route in Sydney's inner-west will soon have access to free data that can show how much their homes have moved.

The technology has been labelled a smoking gun in the fight to prove that cracking in residents' homes is caused by tunnelling.

Leichhardt local Hamish Davidson said he and his family received a letter notifying them they were one of 200 homes added to an expanding impact zone and they have been offered an assessment before construction.

"We're just collateral damage for them," he told 9News.

Tunnelling on the 16.8-billion-dollar project is about to hit Leichhardt, and the M4-M5 link is right under Hawthorne Canal.

"This is absolutely and utterly outrageous and appalling. They should not be allowed to put our homes at risk," Jennifer Aaron from Leichhardt Against Westconnex told 9News.

However, that risk can now be monitored to the finest detail. SAT-SCAN is offering thousands of homes free data to show how much their homes have moved, and when.

"We processed 3000 square metres of Sydney and from that we can see the subsidence, the movement and the accuracy is up to a millimetre," Krish Patel from SAT-SCAN said.

"We can clearly see the movement in the tunnelling in the Westconnex."

Inner West Mayor Darcy Byrne said: "now we have the smoking gun, the satellite data that can arm residents to make their argument and get the compensation they deserve."