Enhancing geospatial information capture in Africa

Enhancing geospatial information capture in Africa

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Introduction
The geospatial technology industry is an emerging sector of the African economy that is expected to see tremendous growth in the coming years. To be able to nurture and sustain this growth on the continent; efforts must be made by individual countries, through continental efforts, and through international bodies to strengthen the technologies that support it. Geospatial data collection has been revolutionised by the use of space technologies like GNSS, VLBI and other space technologies. The birth of the African Geodetic Reference Frame (AFREF), which is an African initiative aiming at unifying all the over 50 Geodetic Reference Networks for all African countries based on the International Terrestrial Reference Frame (ITRF) through the establishment of a network of GNSS permanent stations, is a major geospatial infrastructure. The extension of EGNOS to Africa is an important step that is also putting the continent into the right frame for geospatial data capture. Other major developments that will push the industry to higher level are the square kilometer array (SKA) and the Africa VLBI network (AVN) led by South Africa which brings on board the VLBI technology for very precise positioning.

Spatial component accounts for an estimated 80% of the cost of all information industry (Rizos, 2010) and for the geo-spatial industry to be sustainable, the use of these space technologies should be encouraged to ensure both spatial and temporal accuracy as well as cost-effectiveness as compared to the classical methods of data collection. Using geo-referenced information from heterogeneous sources require data interoperability, specification and standardisation which usually comes with its inherent problems. Efforts should be made by experts to integrate the information from these techniques for the consumption of the geospatial data users.

EGNOS and geospatial Africa
The European Geostationary Navigation Overlay Service (EGNOS) which is part of the first generation GNSS is Europe”s first venture into satellite navigation. It has been designed to complement the American Global Positioning System (GPS) and is a forerunner of the European Galileo. EGNOS disseminates, on the GPS signals in real-time, providing information on the health of the GPS constellation, provides correction data which improves the accuracy of the current GPS services from about 10 m to about 1 m. It also improves the integrity, availability and the continuity of service of the GPS signals. The EGNOS service area includes all European states and has the system-inherent capability to be extended to other regions within the coverage of three geostationary satellites used to transmit the EGNOS signals.

With the triple coverage of the EGNOS Geostationary Satellites, and better elevation angle of these satellites over Africa (Figure 1), there is the need for concerted efforts by African leaders, the scientific community of the continent and the geospatial technologists to come together, meet their European counterparts and harness this augmentation system for the socio-economic benefit of the continent. The successful trial undertaken by the Africa and Indian Ocean (AFI) Planning and Implementation Group under the EGNOS System Test Bed should not be confined to the aviation industry but in other geospatial applications e.g. in Road and Transportation, Agriculture, GIS, Meteorology, Land Surveying etc. Trials in South Africa in the field of transportation attest to the feasibility of EGNOS for these applications.


Figure 1 Footprints of the planned EGNOS Geostationary satellites, showing the Triple coverage over Africa. Source ESA

The performance of the signal-in-space after enabling EGNOS is good enough for many applications on the continent, and geospatial user community will enhance their data capture at a relatively reduced cost, at a faster rate and with lesser effort. Establishing permanent Ranging and Integrity Monitoring Stations (RIMS) on the continent will go a long way to improve the performance of single frequency GPS receivers which are dominant in Africa (Figures 2, 3 and 4).


Figure 2 Accuracy of GPS (L1) without augmentation (Source: ESA)

 


Figure 3: Accuracy of GPS (L1) with EGNOS over Europe and selected region in Africa (Source: ESA)

 


Figure 4: Simulated Accuracy of GPS (L1) with the deployment of RIMS of EGNOS across the continent (Source: ESA)

The roadmap for the implementation of EGNOS in Africa should be expedited and efforts from both the African Union and the European Union should aim at offering the much needed service of this SBAS.

Very long baseline interferometry
With the very high precision of VLBI, various tasks such as geodetic positioning, reference frames interconnections, estimating the crustal movements and other geospatial data capture have attained extremely high accuracies. Converting redundant telecommunication satellite dishes dotted on the continent into radio astronomy antenna by the African VLBI Network (AVN) is a step towards building stronger infrastructure for the geospatial industry on the continent. For example, the conversion of the Ghana’s 32-meter Vodafone communication antenna at Kuntunse near Accra (Figure 5) as part of AVN will enable the precise measurement of the baseline between this antenna and that of any other antenna of interest. This will provide connection with other reference frames on the continent to complement the efforts of AFREF. Similar antennas are to be converted and new ones to be established under the AVN across the continent.

AVN is expected to encourage co-location of research and monitoring facilities, like GPS stations, absolute gravity stations and others for seismic activities, stability of reference networks and many other geospatial applications.


Figure 5: The 32-m satellite communication antenna in Ghana, to be converted into VLBI under the AVN

The square kilometer array
The winning of the square kilometer array (SKA) bid by South Africa in May 2012 to build a network of VLBI stations which will comprise of cluster of antennas spread across thousands of kilometers to form a network is important for the geospatial industry in Africa. The SKA which is a global collaboration of several countries is aimed at providing answers to fundamental questions about the origin and evolution of the universe. The distances between these VLBI stations can however be precisely computed and will therefore enable the study continental drifts, plate tectonics and other geospatial data capture that requires very precise positioning on the continent and in the world at large.

The African geodetic reference frame
The African geodetic reference frame (AFREF) is a unified geodetic reference frame for Africa. When fully implemented, AFREF will be the basis for the national three-dimensional reference networks that will be fully consistent and homogeneous with the International Terrestrial Reference Frame (ITRF) for all the over fifty countries in Africa. A fully operational AFREF will consist of a network of continuously operating; permanent GPS stations that will be located such that a user anywhere in Africa would be within 500 km from a station free of charge. AFREF will include in its service the provision of a unified vertical datum by establishing a precise continental geoid, under the African Geoid Project activities (Neilan, 2005).

A uniform coordinate reference system is fundamental to any project, application, service or product that requires some form of geo-referencing. African countries would benefit greatly from a modern GNSS-based reference system that can be used for national surveying, mapping, photogrammetry, remote sensing, Spatial Data Infrastructure (SDI), Geographical Information Systems (GIS), development programs, and hazard mitigation (earthquake studies, fault motion, severe storms).

Many existing national coordinate systems on the continent are based on ellipsoids which are restricted to the particular country, thereby making cross-border or regional mapping, development, and project planning very difficult (Figure 6). This call for a continental reference system for Africa that will be international, with common goals and objectives throughout Africa, with the commitment of all African countries and the support of international partners. The use of information and communications technology (ICT) and related infrastructure are to be developed along for the project to be sustainable. Development of human capacity must also be a very important component for the sustenance of this laudable initiative.


Figure 6: Illustration of the Africa continent with different reference frames, and that with a unified reference frame

Enhancing geospatial information acquisition
With the introduction of the space technology applications, with SKA and AVN using the VLBI and EGNOS and AFREF using GNSS, It behooves African Scientists, decision makers, geospatial user community to come up with a comprehensive approach to integrate these space technologies, let them complement each other to solve the African geospatial data acquisition problems. The international community has demonstrated the readiness to collaborate and support these technologies in Africa. EGNOS is being extended to Africa by European Commission (Avenant, 2010), AFREF has been supported by UNECA, UNOOSA, IAG, IGS etc although it is an African initiative (Wonnacott, 2008), and SKA is a global project jointly won by South Africa and Australia. Africa must be able to utilize these Space Technologies to enhance geospatial information acquisition for the benefit of mankind.

Role of the New Partnership for Africa’s Development (NEPAD)
The Science and Technology office of the New Partnership for Africa’s Development (NEPAD) which provides overall technical and intellectual leadership for the implementation of the Consolidated Plan of Action (CPA) in scientific programmes on the continent should strengthen its programme on ICT and Space Science and Technology which are the foundation of Geospatial Data Capture. This can be achieved by ensuring that the use of Space Technology Applications is encouraged, for example all National Mapping Organizations should be encouraged to actively participate in space based programmes like AFREF. Policies and programmes are to be put in place to ensure the smooth transition from the classical positioning methods to the space based methods for all African countries. Research and training programmes should aim at not only meeting the demands of the fast growing Space Technology trends but also into methods of mitigating the problems pertaining to Africa like the severe ionospheric and tropospheric delays of the signals in space. Advantage should be taken as a continent of the location of the EGNOS geostationary satellites which gives Africa better and more effective footprints for Space-Based augmentation. EGNOS Ranging and Integrity Monitoring Stations (RIMS) must be deployed to cover the continent such that EGNOS enabled GNSS receivers can enjoy the full benefit of this signal augmentation. Efforts should be made to bring together all space scientist on the continent to play a supporting role for the implementation of these technologies.

The role of National Mapping Organizations
The National Mapping Organizations on the continent should be more proactive, lead the crusade of what AFREF has to offer the geospatial communities. Countries without any programme towards the establishment of a national GNSS Based Geodetic Reference Networks should at least meet the requirement of AFREF, that all countries on the continent must establish at least one Continuously Operating Reference Station as a contribution to the AFREF network. The expertise of the technical team of AFREF will be an advantage to such countries. The unification of all reference networks on the continent cannot be possible if the NMOs are not in favour. Most MNOs want to preserve their data in the old reference ellipsoids for the fear that the transformation into the ITRF may lead to chaos in the unified frame, but with globalization and regional integration, the earlier we move into this new system, at the time when such problems will shared with the proponents of this unified frame, the better.

Establishing an African Space Agency
The coming together at the same time of these major space related projects to the continent should serve as the basis for the establishment of an African Space Agency under the auspices of the African Union, with all member states contributing and benefiting from it. With African scientists collaborating with their international partners to coordinate these space activities, Africa can bridge the gap between the continent and the leaders in Space Technology. African Scientists will then focus on solving problems peculiar to the continent for the effective utilization this technology. Activities in various countries including South Africa and Nigeria should be brought under this agency and expanded to cover the continent.

Conclusion
The four space technology applications which include EGNOS, AFREF, AVN and SKA will be utilized to improve geospatial activities in Africa. Together they will provide various accuracies that will meet the requirements of geospatial applications on the continent. EGNOS enabled GNSS receiver will enjoy a metre level accuracy without cost. AFREF CORS will provide free differential corrections to a user in addition to providing a unified continental reference frame which is a requirement for better geospatial data. The stability of this frame will be supported by with the VLBI technology to be employed by both AVN and SKA projects which will in addition promote inter-connection between continental reference frames to support global geospatial data collection. These space technologies do not only promise to enhance geospatial information capture in Africa but will put it in greater heights in terms of quality.

References

  • Avenant, E. (2011), EGNOS Service Extension to South Africa. Retrieved: 20th October, 2012 from http://www.esastap.org.za/download/space09_2011_pres01.pdf
  • Michel P., H. Secretan. EGNOS System Test Bed. Retrieved : 20th October, 2012 from pro.esa.int/Publications/3rd%20ESTB%20workshop/EGNOS%20SYSTEM%20TEST%20BED%20HSecretan%20PMichel.pdf
  • Neilan, R., (2005). AFREF- Summary of Meetings on Unification of African Reference Frames: Cape Town and Pretoria, South Africa. 28 October – 4 November 2005 AFRICAGIS 2005
  • Rizos, C. (2010). Surveying and Mapping Infrastructures. 125th Anniversary JUPEM Seminar, 14th October, 2010. Kuala Lampur, Malaysia
  • Wonnacott, R., (2008). GNSS as a Multi-Disciplinary Tool for Africa’s Development; African Skies/Cieux Africains, No 12. Retrieved: October 2008 from