Assessment of Positioning with IGS-Real Time Service Data at Enugu, Nigeria

The non-availability of GNSS control points around local regions where access to Continuously Operating Reference Stations (CORS) is difficult or non-available in developing countries, such as Nigeria, has become a major challenge to accurate positioning by differential GNSS method. Also, acquisition of two units of dual frequency GNSS receivers is becoming too costly and unaffordable for users due to economic downturn. With the advent of International GNSS Service (IGS) - real-time service (IGS-RTS) which provides corrections that can be applied in real time, precise point positioning (PPP) with just a receiver unit is now a possibility. This study evaluates this new positioning technique (IGS-RTS) at Enugu, Nigeria, by comparing its results with those obtained from accurate post-processed differential GNSS static observations. The study shows 2-dimensional horizontal root mean square (RMS) discrepancy between both methods at 39% confidence limit is 0.039m and 0.095m at 95% confidence limit. The discrepancy for height was 0.121m at 95% confidence limit. The IGS-RTS corrections were available 100% during the 4 hours 16 minutes duration of observations on six ground control points. Thus, the IGS-RTS data will be very useful in some aspects of cadastral surveys, engineering surveying and GIS (Geographic Information System) in Enugu locality.