OPUS-RS Pair Points: Case Study

Abstract

Referencing small engineering surveys to the national spatial reference system (NSRS) presents advantages in terms of spatially coordinating infrastructure and facilitates the inclusion of the infrastructure in a geographic information system. In cases where the total station is the appropriate tool to conduct the survey, online positioning user service rapid static (OPUS-RS) can be employed to economically establish azimuth pair points to orient the survey to the NSRS. Using OPUS-RS coordinates as observations along with global positioning system (GPS) vectors and total station observations in a least-squares adjustment to establish the azimuth pair points adds robustness to the least-squares adjustment to isolate systematic errors. All the observations contribute to the least-squares adjustment but some observations contribute more than others do. Redundancy numbers can be used to identify those observations that contribute little to the adjustment results. By analyzing the results of three least-squares adjustments, it will be shown that under normal conditions total station observations contribute little to the overall adjustment. Under obstructed conditions total station observations contribute to the vertical precision of the azimuth pair points. OPUS-RS appears to be less susceptible to vertical biases than GPS vectors at obstructed sites.