Abstract
Positioning, based on GNSS reference network technology, is becoming a routine operation within and outside the spatial industry. The expanding user base and diverse range of applications employing this technology can impose significant expectations on the providers of reference network services. In positioning and navigation, the requirement for high accurate coordinate estimates cannot be over-emphasized. This is ensured by the provision of accurate and reliable corrections from the zero-order GNSS reference stations. It is therefore expedient to study the diurnal coordinates of such stations to guarantee reliable information for positioning and navigation applications. In this study, observation data from the Nigerian permanent GNSS continuously operating reference stations located at different states around Nigeria was processed. The hourly and diurnal (daily) coordinate solutions obtained were analysed for the purpose of monitoring the short-term stability of the network coordinates using a two-year (2012-2013) test data. The daily precise point positioning results were processed, analysed, and presented as coordinate time series using RTKPLOT. Python programming language was used to write custom modules to visualize the time series graphs at 30 seconds epochs in order to determine points and epochs where and when the condition for stability defaulted. The stations; FPNO, GEMB, and MDGR were found to be most stable in the Easting component; GEMB and MDGR were the most stable in the Northing component while in the Up component the station GEMB was the most stable. The outcome of the study will assist in detecting stations that are non-operational, performing diurnal PPP processing to detect stations that are unstable, and reporting reference stations that experience sudden coordinate changes. The developed monitoring module can be implemented by the reference stations operators as an automated program for setting up an intelligent alert system to trigger a warning whenever there is unexpected coordinate breach.
Highlights
Global Navigation Satellite System (GNSS) Continuously Operating Reference Station (CORS) networks are being introduced internationally to provide improved access to positioning infrastructure for a wide range of GNSS applications (Janssen and Joel, 2011)
The results of the coordinate variability at each of the NIGNET CORS are presented in the following discussion
CLBR CORS has its highest variation in the months March, April, May, June, September and November with its highest variation ranging from -1.0m to +1.8m in the Easting component, -1.8m to +1.0m in the Northing component and range between -1.4m and +1.8m
Summary
Global Navigation Satellite System (GNSS) Continuously Operating Reference Station (CORS) networks are being introduced internationally to provide improved access to positioning infrastructure for a wide range of GNSS applications (Janssen and Joel, 2011). GNSS provides precise positioning and timing solutions that are unaffected by weather and without the need for a clear line of sight between ground stations Such systems are widely used in various surveying and navigation tasks. Nigeria has established about 15 permanent GNSS Network (NIGNET) or CORS since 2008, which have provided the incentive for the adoption of the geocentric datum in all its geodetic activities (Ali and Samir, 2014). Such stations can conveniently replace the need for a traditional base
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