The NGS OPUS GPS processing system has two versions. OPUS-S is a static version that processes long data sets (over 2 hours) using only three CORS base stations. It calculates the three base lines and says you are in the middle of where they land. They report the position error as the peak-peak difference in the three baselines. I have had fairly poor luck getting good results from it. Most results have p-p errors of 5-10 cm.
OPUS-RS is the "rapid static" system. It only works with data sets from 15 minutes to 2 hours long. It works by solving a least squares fit of data from 9 reference station baselines. When you can get a data set that it accepts the results seem to be quite good. Problems can arise finding nine nearby base stations that can supply references of sufficient quality to solve the equations. One problem with the OPUS system is when it finds something it does not like (like bad reference station data) it stops there and reports that error. It does not check the rest of the user data or reference station data. You wind up spending a lot of effort finding a set of reference stations (or not finding them) that will work. The place where my test antenna is set up is in a very highly treed area (with very high trees) with a two story house 20 feet away, stainless steel fence/reinforced stucco wall 5 feet away, wrought iron fence across the street, etc. LOTS of multipath, very poor sky visibility, etc. I have the antenna mask angle set at 15 degrees. The atmospheric modeling issues are somewhat mitigated by the availability of lots of high quality reference stations within 30km or so. The fact that it could cough up the fixes that it does is rather amazing... ---------------------------------------- _________________________________________________________________ Hotmail® has ever-growing storage! Don’t worry about storage limits. http://windowslive.com/Tutorial/Hotmail/Storage?ocid=TXT_TAGLM_WL_HM_Tutorial_Storage_062009 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
