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

OverviewOverview

• Executive Summary

• Summary of Call for Participation

• Details of Areas of Participation

• Background to AFREF

• References

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.

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

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.

– 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

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.

Active stations being archived at the AFREF Operational Data Center(February 2011)

Progress to Date 2Progress to Date 2

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

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

– 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

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

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

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

- 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

Inter-disciplinary Collaboration Inter-disciplinary Collaboration

Thank you

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

Global Context 1Global Context 1