Comparative Study of Some Online GNSS Post-Processing Services at Selected Permanent GNSS Sites in Nigeria

Many applications in surveying and mapping have been made simpler and more precise due to the advent of GNSS, and thus, the demand for using cutting-edge GNSS techniques in surveying and mapping applications has become indispensable. Online GNSS post- processing services are now available to provide support for users in need of precise point positioning or conventional differential positioning services and without requiring a prior knowledge of GNSS processing software. This study evaluates the performance of some online GNSS facilities with emphasis on observation duration (i.e. 1hr, 2hr, 6hr 12hr and 24hr observations). Three of these online facilities (AUSPOS, GAPS and magic-GNSS) were chosen based on their mode of operation and were evaluated at the location of five permanent GNSS stations in Nigeria. The study cut across two epochs in the year 2014 (i.e. seven days each in the months of January and July). Results in this study indicate that users can expect reliable results from these online services and their accuracy is within allowable limits for mapping applications in Nigeria. The similarity of the results between all of the services used is amazing, thus further demonstrates the robustness of the algorithms and processes employed by the different online facilities.