| Popis: |
A reconciling vertical datum is fundamental for the seamless integration of multi-source hydrographic data. Based on the analyses of the current vertical datums used for hydrograph, this paper presents a new scheme to create a reconciling vertical datum. To resolve the problem of integrating geospatial data referred to different vertical surfaces, an ellipsoidal datum is adopted as a universal master reference surface; A (quasi) hydroid is defined and the method which determine the quasi hydroid is then introduced; The quasi geoid and hydroid are adopted as client datums. On the basis of the determination between the master datum and the client datums, the data derived from different datums can be aggregated seamlessly and discretionarily. Two methods which can transform depth data from one vertical datum to another when quickly aggregating hydrographic data are suggested, one is identical transformation parameters based on hierarchical grid, and the other is interpolation based on position. |
