It would expend more labor and material in the traditional precision leveling.

This paper introduced the process of the construction of fiducial system for modern surveying of Wuhan city on the whole,then explained and analysed the data process and test of WHCORS、high accurate GPS reference network、accurate level net and areal geoid refine in Wuhan.

This paper summarized the background and basic content of the construction of fiducial system for modern surveying of JiNan,then detailedly introduced the data process and test of high accurate GPS reference network、accurate level net and geoid refine and JNCORS,and the corresponding innovation and application are analysed.

Aimed at different understanding and view point,based on precise level monitoring,GPS techniques and systematic analysis of in situ monitoring data of scores of years,the authors put forward a perspective of surface subsidence has certain self recoverable capability,summed up the range of surface recoverable subsidence threshold,narrated rational method and in situ monitoring essentials.

In order to monitor land subsidence in Tianjin area,a GPS network was established in 1995 as a complementary means of the precise leveling.

The relative altitude variations at these points were analyzed using ten years replicated observations in this paper,and they were compared with the results of precise leveling by the authors.

On the basis of the research on the contrast between GPS and precise leveling from 1995 to 2004, the actual accuracy of the two methods is tested.