Implementation of NTRIP and Management System in NIGNET Network

• Autor(a) principal: Okorukwu, Williams Okey
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/5840
• topic: Gnss; Management System; Nignet Network; Ntc; Ntrip; Real Time Correction; Rtcm; Rtk; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Eletrotécnica, Eletrónica e Informática

Nowadays, several applications require knowledge of their position in real time in order to achieve its intended design result. Global Navigation Satellite System (GNSS) has proved to be the most effective and efficient way of positioning in a global scale, using a GNSS receiver, to determine ones position with an accuracy of few millimetres. However, for centimetre-level accuracy such as Precise Point Positioning (PPP) one must use differential mode (directly or indirectly). In case of differential position, in Post-Processing (PP) or Real Time Kinematic (RTK) observation, one uses the GNSS observations from nearby Base stations, of which the position is well known, to determine ones relative position. Whichever way, the observations need to be corrected either by PP or in real time correction method in order to achieve higher positioning accuracy. These corrections, in the case of RTK mode, are mostly GNSS pseudoranges (distance measurements), positional (ephemeris) data and models, like ionosphere. These are simultaneously measured to all satellites in view, and using the known position of the receiver's antenna from each satellite, the errors in the pseudoranges and models are calculated at both the Base and the Rover GNSS receiver stations. These errors are converted to correction data at the Base station and broadcasted to Rover GNSS receivers in real time. As several applications are emerging to solve many positioning problems, the need to improve positioning solutions in real time is increasing. However, issues of transmitting these real time correction data has been a matter of concern. This is because, the use of several methods of transmitting real time correction data like Frequency Modulation Radio (FMR) has proved ineffective in terms of cost, efficiency and coverage. The current advancements in Internet and telecommunication systems have attracted the interest of researchers in using Internet as a Communication channel for the distribution of GNSS correction data in real time. Networked Transport of RTCM via Internet Protocol (NTRIP), which is a protocol that supports the streaming of GNSS correction data via the Internet for real time positioning, appears to be one of the best solutions for GNSS real time correction data distribution, because of the improved availability and coverage of Internet. This thesis focuses on the implementation of NTRIP protocol in NIGNET Network, which is a network of GNSS permanent stations in Nigeria, West Africa. It deals with the development of a management system for real time positioning services. A test bed approach, which was setup in Space and Earth Geometric Analysis Laboratory (SEGAL) was used during the implementation process. The BKG Standard NTRIP Caster, which runs on Linux Operating System was used in the implementation, and the management system was developed using the PHPStorm, Mysql, and NTC applications. The NTC application was developed in order to integrate the NTRIP system with the website which serves as a management system. The management system offers the administrator the flexibility to manage the NTRIP system, GNSS source generating data and users activities in a friendly web interface. In addition, a billing/payment mechanism integrated with PayPal online payment platform was incorporated in the management system. Furthermore, its viability was tested by carrying out test observations in RTK mode using Trimble R8 GNSS receiver and smart mobile phone. This was done by activating the Internet connectivity of the GNSS receiver using the smart mobile phone and configuring it to the mountpoint CLBR, which is a NIGNET station's mountpoint maintained by the NTRIP and Management System. Using the services of the NTRIP and Management System, real time correction data from CLBR station was able to be streamed to the GNSS receiver in RTK mode via the Internet. So far the results of the preliminary test are not yet satisfactory in terms of accuracy, due to the distance, but logistic constraints did not allow us to do the planned tests within at most 40-50km from CLBR. Nevertheless, the NTRIP and Management System was able to perform its designed purposes and can be used operationally for observations nearer the Reference Stations.