Heuristic weighting and data conditioning in the National Geodetic Survey Rapid Static GPS software

NOAA's National Geodetic Survey (NGS) has developed the Rapid Static GPS software for use as the major processing engine in the OPUS-RS utility (online positioning user service-rapid static) (http://www.ngs.noaa.gov/OPUS/OPUS-RS.html). The software was written specifically to support the computation of static positions from GPS tracking sessions as short as 15 min, while using reference station data from the NGS archive of continuously operating reference stations (CORS). When the reference stations are close (50 km) to the user's station, it is relatively easy to obtain an accurate solution. However, the CORS stations in the NGS archive are separated by 200 km or more in many areas of the country. In this situation, much care must be taken in conditioning the data sets and in selecting appropriate weights for the observations and constraints. This paper describes methods and weights that have been found to work well for most (but not quite all) data sets, and, therefore, can be used in an automated procedure such as OPUS-RS.