The surveyor doesn't know the reason for the design elevation.

Not fully prepared for communication problems.

1. Inadequate preparation: the surveyor did not get complete or accurate design elevation information. Because the designer did not provide relevant information, or the surveyor was not updated in time.

2. Communication problem: There are communication problems between surveyors and designers, resulting in the design elevation information not being clearly conveyed or misunderstood. This is because the designer did not fully explain the elevation requirements, or the surveyor did not read and understand the relevant design documents carefully.