Lagos digital map ready, links navigational satellite
By Adeyemi Adepetun
AS the world advances by the day via various developments coming from the advancement in technology, Lagos in particular, is dictating the pace in Nigeria with its recently completed Continuous Operating Reference Station (CORS).
The COPS is a Global Navigation Satellite System (GNSS) which operates continuously from a permanent and stable location; it tracks dozens of Global Positioning System (GPS) and GLONASS Satellites, receives and stores the data transmitted by the satellites in real time, the software monitors the performance of CORS equipment at the reference station, manages the data, processes it and removes all errors and transmits this data to all users in a particular location in real-time.
Though, around the world today, there are now many networks of GNSS Reference Stations delivering sub centimetre accuracy positioning to users, mostly surveyors, in real time, the benefits of real-time, accurate and widespread location services provided by GNSS Reference Stations is compelling, their roll-out is constrained by the lack of necessary funding to provide the required infrastructure to deliver these precise positioning services.
The positions of these CORS sites help define the National Spatial Reference System (NSRS). The NSRS provides a consistent national coordinate system to support mapping, charting, navigation, boundary determination, property delineation, infrastructure development, resource evaluation surveys and scientific applications.
The CORS programme primary objective is to allow users to improve their positional coordinates in post-processing activities by providing access to the CORS data set and software tools such as OPUS. In other applications, CORS data is used for modeling the water vapour content in the troposphere and for modeling total electron content in the ionosphere.
Only recently, the Lagos State Governor, Babatunde Fashola accepted the completion of the state's first operational Continuously Operating Reference Station by the Nigerian based company - GeoQinetiq Limited. With this system, the state government is on the trail of establishing a world-class, ultra modern technologies to provide a solid basis for the transformation of the state and providing the technological foundations for successful implementation of the Lagos Mega City Project.
However, sequel to the Lagos CORS initiative, in June, 2007, Fashola had set up a five man advisory committee of experts to deliver a fully digital mapping and enterprise Geographic Information System (GIS) for Lagos State. This committee had the former Surveyor- General of the State, M. A. O. Durowoju as chairman. That committee was mandated to examine and recommend the best sustainable mapping and GIS solution for Lagos State.
The report of the advisory committee was presented to the executive council meeting of Monday 10th September 2007 and a technical committee under the Chairmanship of Dr. Femi Hamzat, the Commissioner for Science and Technology was constituted to examine and recommend the best sustainable mapping and GIS solution for Lagos State.
For convenience and operational effectiveness, the Lagos State Digital Mapping/Enterprise GIS was broken into seven major components and contracts awarded: Geodetic Control and Digital Aerial Photo Acquisition, determination of Geoid Model and Establishment of Continuous Operating Reference Station (CORS), Orthophoto, Contour lines and Digital (vector) Mapping, GIS Database and Enterprise GIS, bathymetry Survey of Lagos Lagoons and Creeks, Supply of Equipment and Training and Public Enlightenment & Education.
In the words of the Managing Director of GeoQinteq Limited, Juliet Ezechie, "this initiative will help build a new Lagos infrastructure, help in tackling land management, poor town planning practices and contribute to alleviating road congestion, road safety and improving public transport,"
Ezechie said that CORS project would help to supply the Global Navigation Satellite Systems (GNSS) reference stations and networking software under the state's plan to create a network of permanently installed Continuously Operating Reference Stations (CORS), adding that the system was based on the ultra-modern, 'future-proof' Leica GRX1200GG GNSS reference station receiver, along with Spider GPS network control software, which would be incorporated into an integrated network of base stations deployed at strategic locations across the state, providing very high-accuracy real-time and post processed data for a wide range of surveying and construction applications.
She added that GNSS CORS were important enhancement to a wide range of GNSS surveying, mapping and positioning activities, which can improve the efficiency and accuracy (under 1 cm) of surveyed positions, as well as helping to deliver a host of derived data products that in turn make possible additional GNSS applications.
To her, the key objectives of the Lagos CORS are to deliver a functional state of the art high accuracy Active GNSS Reference Station to be housed and controlled from the surveyor generals office, Lagos State, to provide the basis for accurate location services underpinning the digital mapping of Lagos State, to provide a backbone for the development of Geographic Information Systems (GIS) in Lagos State, to increase the productivity of GNSS/RTK survey work in Lagos State, to contribute to the achievement of Nigeria in the development of AFREF and to provide a revenue generating mechanism for supported GNSS Survey work in Lagos State.
The GeoQinteq MD however added, for its efficiency, the CORS systems must be available every second of every day, 365 days of the year and to overcome the vagaries of the unreliable power system in Nigeria, GeoQinetiq proposed a system that uses power from the public utility PHCN when available, but this power is channeled through a low voltage monitor, which detects power or imminent power failure, that at such times, the system automatically switches over the to the four-array solar power system in the daylight hours, or automatically takes power from an uninterruptible power supply module which is charged alternatively by the public power source or the solar energy modules.
