Survey and mapping office staff who opt for corporatisation will have two years to decide whether to leave the Government for good while working in the corporation. But the 1,200 employees were warned yesterday that they would lose their job security once they gave up their civil servant status. About 600 staff yesterday demonstrated outside Legco, where officials briefed lawmakers on plans to make the Lands Department's Survey and Mapping Office a money-making business. While withholding detailed business plans until next month, officials have estimated that corporatising the office would bring about a windfall of $900 million in 10 years. At the Legco public service panel meeting, Lee Cheuk-yan, of the Confederation of Trade Unions, asked if staff could switch back to the civil service if the company lost money. Director of Lands Bob Pope said employees could opt for voluntary retirement and start afresh with the corporation or be seconded to the new body and adopt a wait-and-see attitude in the first two years. He admitted the jobs would not be as stable as they were in the Government.