Discussions about how to determine weight in NPP's construction control surveying

It's important to determine the proper proportion of different sorts of observations' weight in order to improve the calculation quality during high precision engineering surveying. Set up a triangulateration control network with high accuracy electronic total station is commonly used in nuclear power plant(NPP) projects and observations are adjusted with experienced weight within which the observations' deviation come from experience instead of the practical conditions. So Helmert variation estimation has been suggested to process the data instead of the traditional method and the relationship between them has been shown by an example which comes from a real project, and some beneficial suggestions are also given in order to use the latter more efficiently. (authors)