AFREF
AFRICAN GEODETIC REFERENCE FRAME
A
A Modern
Modern and
and Unified
Unified Reference
Reference Frame
Frame for
for Africa
Africa
Ludwig Combrinck
On behalf of the AFREF Steering Commitee
International
International Symposium
Symposium on
on Global
Global Navigation
Navigation Satellite
Satellite Systems,
Systems, Space-based
Space-based and
and Ground-
Ground-
based
based Augmentation
Augmentation systems
systems and
and Applications
Applications
Berlin,
Berlin, Germany,
Germany, 11-14
11-14 November
November 2008
2008
Introduction
Introduction
Development approaches in Africa are geared towards
continental and regional economic and political integration
-AU
-NEPAD
-COMESA
-SADC
-EAC
-ECOWAS
This requires uniform geo-spatial information
Problem
Traditionally each country has its own
geodetic reference system
(system1 ) (system2)
Maps in neighbouring countries do not match at the
national boundaries
Modern GIS data derived from GNSS cannot be geo-
referenced on old maps
PROBLEMS - CONSEQUENCES :
A multitude of different datums, different ellipsoids and
different projections
Confusion within countries as to appropriate datums,
projections and transformations to use
Confusion and conflict regarding international borders
Confusion and delays in cross-border projects -
boundary definition, transport corridors, mapping,
exploitation of mineral resources
Impact of Reference Mismatch
Map dated 1989 Map dated 1957
WGS-84 NAD-27
Consequences of using reference systems
that are not consistent !
Source: Zurich-
Zurich-American Insurance
Solution
Solution
•Move from National Reference Systems to
Regional or Global Reference Systems
National Systems Global Systems
Solution
Solution
Non-uniform systems Uniform system
GNSS
+
ITRF
Objectives
Objectives of
of AFREF
AFREF
• To establish a continental reference system as a
basis for national reference networks.
• To establish permanent GNSS base stations such
that users will be within 500km of a base station
and that data is freely available to all users.
• To realize a unified vertical datum and to support
efforts to establish a precise African geoid.
Organizational
Organizational Principles
Principles
The structure reflects the broad concepts of
AFREF that:
• It is to be designed, managed and
executed from within Africa;
• It is to be organized on a regional
basis;
• It is to be executed at the national
level
Organizational
Organizational Structure
Structure
UN ECA CODI
CODI GEO International
Scientific Partners
advisory
Group Steering Committee
RECTAS RCMRD AOCRS
National Mapping Organisations & Other GNSS Stake
Holders
IMPLEMENTATION STRATEGY
•The establishment of a frame work of active GNSS stations
• Computation of AFREF solution
IMPLEMENTATION STRATEGY
•The densification of the network at national level
Frame Relay continuous Thohoyandau
stream
Ellisras
ISDN Daily download Pietersburg Phalborwa
BOTSWANA MOZAMBIQUE
Int GPS Service Stations
Nelspruit
Mafiken
g Pretoria
Middelburg
NAMIBIA Hartebeesthoek
Kuruman SWAZI
Ermelo
Upington Ulundi
Bethlehem
Bloemfontein Ladysmith
Kimberley
Springbok Pietermaritzburg
LESOTHO
Prieska De Aar Durban
Aliwal
Beaufort West North
Calvinia Queenstown Umtata
Graaff-Reinet
Sutherlan
Langebaanw
d
eg East
London
Cape Town
George Port Elizabeth 200 KM
Hermanus
Current Status of Network
The following countries have already
established at least one Continuous
Operation GNSS Reference Stations
(CORS);
Algeria, Angola, Botswana, Burkina-Faso,
S. Tomé e Príncipe, Egypt, Mozambique,
Ghana, Kenya, Benin, Morocco, South
Africa, Namibia, Zambia, Ivory Coast,
Tanzania, Ethiopia, Malawi, Mauritius,
Niger, Nigeria, Uganda and Madagascar.
IMPLEMENTATION STRATEGY
•The development of a refined geoid model for Africa
IMPLEMENTATION STRATEGY
traditional vs AFREF
Existing networks AFREF
Based on old technologies Establish National
Most monuments destroyed Networks based on
Not consistent GNSS technology and
Heights not accurate with Global
Location connection.
• Hill tops
Compute conversions
• Not safe
factors to/from
• Not easy to access
existing networks
to/from AFREF
IMPLEMENTATION STRATEGY
National GNSS Networks
National working groups
Establish New network
Connection to existing network
Establish GNSS Centre
AFREF STRUCTURE ON REALIZATION
DGPS
Real Time Users
Telecom Sat
DGPS GSM / GPRS
-RTK
Post Processing Users
Network
Control Centre
GSM
FTP/ Web Server GPRS
internet
Field CORS etc
Applications
Applications in Land Surveys
AFREF Base
Station
Applications in Mapping
Real time Differential
corrections will improve
GPS solutions for
Mapping
AFREF Base
Station
Will provide
Ground control
for Mapping
Applications in Water Navigation
Real time Differential corrections will improve
GPS accuracy and precise docking
AFREF Base
Station
Applications in Air Navigation
AFREF base
stations(s) will
provide coordinate
corrections to planes
for precise airport
location and landing
Applications in Crustal dynamics
340˚ 0˚ 20˚ 40˚ 60˚
ARAB PLATE 20˚
AFRI PLATE
SOMA PLATE
Mid Atlantic Ridge(38mm/yr)
0˚
-20˚
r)
/y
m
9m
(1
IR
-40˚
SW
GPS data from AFREF base stations will be
used to continuously monitor earth crustal
movements.
Required resources
Trained technical staff – 2 per station.
Positioning equipment – GNSS receivers – USD
20,000 per station.
Reliable power supply.
Computing facilities.
Communication facilities –Internet, VSAT, telephone.
Present
Present status
status
•Call for Participation sent out •19 Countries established
permanent stations
(28 responses received)
CALL FOR PARTICIPATION
in the
UNIFICATION OF AFRICAN REFERENCE
FRAMES
The AFREF Project
2005-2010
Committee on Development Information, Geo-
Information Subcommittee
(CODI-GEO)
United Nations Economic Commission for Africa
(UNECA)
http://geoinfo.uneca.org/afref/
Endorsed by:
International Association of Geodesy (IAG)
International Global Navigation Satellite System
Service (IGS)
United Nations Office of Outer Space Affairs
(UNOOSA) Federation of International Surveyors
(FIG)
August 2005
Kenya Aug 2008 on the way to training......
Training at RCMRD Kenya
Adequate facilities at RCMRD
But also time for networking,
sight-seeing and shopping
Present
Present status
status
• 3 technical workshops and 3 training courses (latest
august 2008, Kenya) have been held.
• AFREF Station Guidelines published.
AFREF
Permanent Stations Guidelines
Requirements and Installation
Rui Fernandes & Salah Mahmoud
Edited by H.O.Farah
Present
Present status
status
•AFREF Secretariat established at RCMRD
•AFREF Web site established
http://geoinfo.uneca.org/afref
•AFREF quarterly Newsletter launched
AFRICAN GEODETIC
REFERENCE FRAME (AFREF)-
NEWSLETTER
Secretariat: Regional Centre for Mapping of Resources for Development (RCMRD)
AFREF News Letter No.4 Ruaraka
P.O.Box 632-00618, e-mail: afref@rcmrd.org
Nairobi, September
Kenya. Tel:+254-20-8560227/8561775Fax:254-20- 2007
8561673
Present
Present status
status
•Data Holding and Analysis Centers to be established
( HartRAO station and Regional Centres)
Way
Way Forward
Forward
More Publicity of AFREF initiative.
Capacity building – manpower and equipment at
national level .
commitment from National Mapping
Organizations .
Support from international partners.
Build capacity in AFREF data analysis centres.
Compute first official AFREF Coordinates in 2009
Non-uniform systems Uniform system
GNSS
+
ITRF
THANK YOU
http://geoinfo.uneca.org/afref
