5.9　Establishment of Three-dimensional Digital Model for Route

5.9.1　Various methods including stereoscopic viewing and image identification shall be used for input of annotation data to ensure the input data can be interpreted accurately and described clearly.The main content to be entered shall include the power lines，communication lines，independent surface features，piping and auxiliary facilities for outdoor annotation，which shall be in the format of electronic documents.

5.9.2　When establishing the digital model of ground elevation，the following requirements shall be satisfied:

1　The digital ground elevation model shall be registered using the stereoscopic model of images，and man-machine mutual editing shall be carried out to correct the errors caused by automatic match and the vegetation and building heights.

2　The grid spacing of digital ground elevation model shall not be less than 10m.

3　When combining the DEMs within a flight strip and combining different flight strips，an overlapped band of at least two grids shall be maintained.

4　The metafile of data shall be accurate and complete.