BEIJING -- China launched its Fifth National Monitoring of Desertification and Sandification on Friday.

The State Forestry Administration said the campaign to collect information on the status and dynamics of land will last 18 months and combine land-surface survey with satellite remote-sensing technology.

The results will provide scientific bases for policy-making and help combat desertification and sandification, said the administration.

Zhang Yongli, the administration's deputy director, asked forestry authorities at various levels to make sure the results are correct and reliable.