GNSS Sky Visibility Planning and Dilution of Precision Analysis for EOS Ground Station Selection for Nigeria Space Programme

Abstract

The establishment of Earth Observation Satellite (EOS) ground receiving stations in parts of Nigeria and other parts of the globe, similar to the Indian Remote Sensing (IRS) model will enhanced global tele-commands, precise EOS tracking, data transmission and distribution of NigeriaSat data, which will enhance global-scale data awareness, usage and higher financial returns for Nigeria. This study therefore attempts the application of Global Navigation Satellite System (GNSS) sky visibility planning and dilution of precision analysis technique to select optimal location for EOS ground station(s) in Nigeria. The Nigerian Geodetic Network (NigNet) GNSS Continuously Operating Reference Stations (CORS) RINEX data of February 2012 and Trimble Total Control (TTC) software were used for the determinations of the baselines and positions of the 11 available CORS. The technique of GNSS sky visibility planning and dilution of precision (DOP) was adopted because signals from satellites behave in similar pattern in the atmosphere, so poor visibility in GNSS signal in a particular observation window translates relatively to poor orbit definition signal for an EOS. Based on Jon's rating of DOP values [1= ideal; 2-3 = excellent; 4-6 =good; 7-8= moderate; 9-20=fair; 21-50= poor)], the DOP values for the stations across Nigeria can be adjudged to range between excellent and good for ground receiving stations. However, the overall results showed that, GEMB on ellipsoidal heights of 1795.7857m has the most suitable DOPs and sky visibility plan for ground receiving sites; followed by CGG Toro (916.7853m) and RAMPOLY Maiduguri (702m). The sky visibility analysis showed availability of an average of 9 GPS and 2 GLONASS constellation satellites to receivers at elevation angles of 10o-15o between 6:00hrs and 24:00hrs daily across Nigeria. The approach of EOS ground receiving station suitability analysis demonstrated in this study is recommended for the Nigerian Space programme in EOS ground-based antennae farm establishment. It is also relevant in the densification of GNSS reference stations by public-private organizations for geoinformation development, engineering infrastructure tracking and navigation at state and local government levels across the country