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United Nations Economic Commission for Africa
CODIST II - Geo
R Wonnacott
Addis Ababa
2 May 2011
United Nations Economic Commission for Africa
CODIST II - Geo
R Wonnacott
Addis Ababa
2 May 2011
Call for Participationfor
The Processing of AFREF GNSS Data
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OverviewOverview
• Executive Summary
• Summary of Call for Participation
• Details of Areas of Participation
• Background to AFREF
• References
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BackgroundBackground
• Fundamental point of departure for projects, services or products requiring geo-spatial information is a uniform & reliable co-ordinate reference frame.
• Over 50 countries in Africa each with their own geodetic reference system and frame and some with 2 or more systems.
• Although there are many areas of conflict there are also areas where peace has been restored and require a lot of development.
• It is known that many private commercial enterprises are setting up their own reference frames particularly in the oil and mining industries.
• AFREF is, therefore, an African initiative to unify the geodetic reference frames of Africa based on the ITRF through a network of GNSS base stations at a spacing such users will be at most within ~1000 km of a base station.
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International EndorsementInternational Endorsement
• UN ECA CODIST (Committee on Development Information, Science & Technology)
– Have adopted the Windhoek Declaration
– Created a Working Group to deal specifically with AFREF
• UN OOSA (UN Office for Outer Space Affairs)– Have recognized the importance of AFREF for variety of applications
– Supported travel for some AFREF activities
• IAG (International Association of Geodesy)– Have created structures to co-ordinate the project and provide
technical assistance and expertise
• IGS (International GNSS Service)– Has strong commitment to support AFREF
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Objectives of AFREF 1Objectives of AFREF 1
– To determine a continental reference system for Africa consistent and homogeneous with the global reference frame of the ITRF as a basis for national 3-d reference networks.
– To realize a unified vertical datum and to support efforts to establish a precise African geoid.
– To establish continuous, permanent GNSS base stations at a spacing such that the users will be within 1000km of a base station and that data is freely available to all nations.
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– To determine the relationship between the existing national reference frames and the ITRF to preserve legacy information based on existing frames.
– To provide a sustainable development environment for technology transfer so that these activities will enhance the national networks and other applications.
– Assist in establishing in-country expertise for implementation , operation, processing and analysis of modern geodetic techniques, primarily GNSS.
Objectives of AFREF 2Objectives of AFREF 2
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Progress to Date 1Progress to Date 1
• The AFREF Operational Data Centre (ODC) is currently archiving on a daily or near daily basis data from nearly 62 permanent GNSS base stations at average of 31 stations daily ( as at mid-April 2011).
• Data is freely and openly available to all users.
• Project reached the stage where a computation of all available stations can be carried out.
• National Mapping Organizations will be able to use results plus available GNSS data from ODC to compute National Reference Frames based on ITRF.
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Active stations being archived at the AFREF Operational Data Center(February 2011)
Progress to Date 2Progress to Date 2
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Number of activities underway to install permanent base stations or move towards ITRF:
Algeria AngolaBenin BotswanaCameroon EgyptEthiopia GhanaKenya LesothoMalawi MorocoMozambique NamibiaNigeria RwandaSouth Africa SwazilandTanzania TunisiaUganda Zambia
Progress to Date 3Progress to Date 3
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As agreed at CODIST I (April 2009), an Operational Data Centre has been established.
– www.afrefdata.org or ftp.afrefdata.org
– Data from 62 (mid-April 2011) continuous stations brought together from number of data centres into one place. Data centres include:
• CDDIS
• HartRAO
• NGS
• TrigNet
• UNAVCO
• Nignet
• SEGAL
• Plus data from 3 stations being directly downloaded from receivers
Progress to Date 4Progress to Date 4
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– Number of stations listed for which no data available - it is known that these stations are operating but data not
available.
– Number of campaign stations listed hence only periodic data available .
Progress to Date 5Progress to Date 5
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Processing and analysis of data from the network of GNSS base stations to produce a continental reference frame:
– Computation of network of fiducial stations based on well established stations with long term reliability and publically available data;
– An initial processing will provide set of co-ordinates for use at National level - frozen in time;
– In addition will provide ongoing processing to maintain network and provide set of velocity vectors and to make allowance for the addition of new stations;
– Processing to be done using IAG guidelines.
Areas of Participation 1Areas of Participation 1
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Computation of national networks based on the continental reference frame:
– Major objective project is conversion of National geodetic networks to AFREF and hence ITRF;
– NMOs will have to occupy number of strategically placed points whose co-ordinates are well established in the National frame using GNSS;
– Processing could either be as series as campaign or using permanent stations to convert / transform current frame to AFREF;
– Respondents will have to set out proposed strategy.
Areas of Participation 2Areas of Participation 2
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Training and capacity building of geodesists and surveyors in NMOs and Universities
–Respondents to CfP will be required to address the following:
– Describe the form of training whether for individuals or components of NMOs;
– In case of individual training, will training lead to some form of qualification?;
– What level of sponsorship will be offered, if any? ;
– Proposal must describe level of expertise required to undertake training; and
– Any other details not covered in the above.
Areas of Participation 3Areas of Participation 3
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- Call for Participation includes a section on the background to AFREF which will not be covered in this presentation.
- Commitment to project to be at least 5 years to create an environment for sustainable environment.
- Proposals to be evaluated by panel of independent experts.
- The CfP also covers multi-disciplinary aspects of AFREF such as collaborations with;
- Africa Array - seismology
- Africa Monsoon Multi-disciplinary Array-GPS (AMMA-GPS) – meteorology
- Scintillation Network Decision Aid (SCINDA) – space weather
- Dates for submission of CfP proposals still to be finalized.
GeneralGeneral
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Inter-disciplinary Collaboration Inter-disciplinary Collaboration
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Thank you
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Global distribution of four space based positioning techniques available for realization of International Terrestrial Reference
Frame (ITRF) + GPS Only ; + DORIS only; + SLR Only; + VLBI Only
4 Techniques; 3 Techniques; 2 Techniques
Global Context 1Global Context 1
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Global Context 1Global Context 1