Call for Participation
for
The Processing of AFREF GNSS Data
United Nations Economic Commission for Africa
CODIST II - Geo
R Wonnacott
Addis Ababa
2 May 2011
Overview
• Executive Summary
• Summary of Call for Participation
• Details of Areas of Participation
• Background to AFREF
• References
Background
• 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 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 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.
Objectives of AFREF 2
– 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.
Progress 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.
Progress to Date 2
Active stations
being archived
at the AFREF
Operational
Data Center
(February 2011)
Progress to Date 3
Number of activities underway to install permanent
base stations or move towards ITRF:
Algeria
Benin
Cameroon
Ethiopia
Kenya
Malawi
Mozambique
Nigeria
South Africa
Tanzania
Uganda
Angola
Botswana
Egypt
Ghana
Lesotho
Moroco
Namibia
Rwanda
Swaziland
Tunisia
Zambia
Progress to Date 4
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 5
–
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 .
Areas of Participation 1
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 2
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 3
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.
General
-
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.
Inter-disciplinary Collaboration
Thank you
Global Context 1
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 1