[IGSMAIL-3208]: 'AFREF' - Continental Reference System for Africa
Ruth E. Neilan
ruth.neilan at jpl.nasa.gov
Wed Feb 14 15:45:18 PST 2001
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IGS Electronic Mail 14 Feb 15:45:20 PST 2001 Message Number 3208
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Author: Ruth Neilan & Claude Boucher
Dear colleagues,
Enclosed below is the text of a letter describing the interests and
motivations for establishing a continental reference system for
Africa - 'AFREF'. This letter is being widely distributed by email
and by hardcopy to as many additional interested persons within
Africa and elsewhere as we have been able to obtain. Please feel
free to forward this message. We plan to compile a mailing list for
this initiative over the coming months, instructions on how to be
included in this directory are at the end of this message.
The PDF version of this message contains a map, and the directory
update form,please see:
http://igscb.jpl.nasa.gov/mail/afref/letter.010214.pdf
As this message is sent to multiple mailing lists, we apologize if
you receive more than one copy.
with best regards,
Ruth Neilan and Claude Boucher
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February 14, 2001
Subject: Continental Reference System for Africa, African Reference
System 'AFREF'
Dear colleague,
A number of discussions over the past year strongly suggest that it
is time to initiate an effort towards realizing a modern continental
geodetic reference system for Africa. The International Association
of Geodesy (IAG) Commission X on Global and Regional Geodetic
Networks and the International GPS Service (IGS), through contacts
with various organizations and people within Africa, support the
establishment of such a project within Africa. This letter solicits
your interest in such an effort.
The most effective way to achieve a robust and globally consistent
continental reference system is through the technology of the Global
Positioning System (GPS). The explosive growth of GPS applications
and the economics of GPS make it the technique of choice for
sustainable geodetic operations within Africa. The IGS, as an
existing IAG service, provides high quality GPS data, products and
information resources that can further the realization of an African
continental reference system. The IGS strongly supports the charter
of the International Terrestrial Reference System (ITRS), part of the
International Earth Rotation Service (IERS), which relies to a great
extent on IGS and GPS for densification of the International
Terrestrial Reference Frame (ITRF). We recall that ITRS is the global
terrestrial reference system officially adopted by the IAG, and that
the WGS84 (World Geodetic System 1984) reference system of the GPS,
which is widely used by several communities, is now identical to ITRS
at the centimeter level.
Due to the permanent global infrastructure of the IGS, a flexible
approach can be designed to accomplish a continental reference system
for Africa. First, permanent GPS stations within Africa are or can
be linked to the highly consistent daily processing of the IGS. A
sparse number of these currently exist and provide a backbone of
precise control - it would be clearly beneficial to increase the
number of permanent IGS stations within the African area (see IGS map
at http://igscb.jpl.nasa.gov/network/netindex.html). Secondly,
additional stations are required for the regional densification such
as establishing GPS national networks through either permanent or
semi-permanent GPS networks; or in specific areas through campaign
style or single point measurements with mobile GPS receivers.
It is important to note that contrary to previous GPS network
observations where it was important to have an entire network observe
simultaneously, it is no longer necessary to do so. Through the
continuity and permanency of the global infrastructure provided by
the IGS, GPS observations taken at one time can be linked to
observations taken at a subsequent locations and times with little
degradation of accuracy. In fact, given the vast extent of Africa and
logistical difficulties of coordinating between more than 50 nations,
a more regional approach tied to a fiducial continental network seems
more feasible and prudent.
All subsequent analysis and results can be based on the precise
products and orbits produced by the IGS to position stations in the
ITRF, as well as providing the basis for transformations between it
and any national geodetic datum. By following IGS/ITRF
recommendations and conventions, centimeter level 3-dimensional
positioning can be obtained within this framework. The applications
of realizing this have vast potential from geodesy, mapping,
surveying, geoinformation, geomanagement, natural hazards mitigation,
Earth sciences, etc. Additionally, the project will provide a major
springboard for the transfer and enhancement of skills in surveying
and geodesy and especially GPS technology. Surveyors and geodesists
from participating African countries will be strongly encouraged to
actively participate in all phases of the project.
Over recent years there are models of other continents and countries
realizing a continental reference system. For example, EUREF, the
European Reference System for Europe, and SIRGAS, Sistema de
Referencia Geocentrico para America del Sur, a continental reference
system throughout South America. Currently a new initiative to join
reference networks within North America is being pursued by the
national agencies and organizations within the U.S., Canada, Mexico,
the Caribbean nations, etc.
It is clear that the leadership for such a project must come from
within the African professional community. Preliminary meetings
within Africa to discuss project interest and approach will be
initiated. IGS and IAG experts and advisors will be available to
advocate the formation of such a project within Africa. The IGS and
IAG would be willing to attempt coordinating international resources
and assistance to facilitate such an activity. It would be important
over the longer term to ensure that this project will produce
established, dedicated analysis and data information centers, links
between African agencies and links with international organizations.
Venues for such organizational meetings are currently being
considered and it is envisioned that a series of discussions may take
place as opportunities arise at scheduled conferences and meetings.
On behalf of IAG and IGS, we would like to invite your participation
in this effort. Please respond to this letter by sending a statement
of your interest along with your contact information to the address
below or email to igscb.jpl.nasa.gov with subject 'AFREF Interest'.
A primary contact list will be compiled from the responses; these
people will be included in any correspondence and notified of future
meetings to discuss plans and organization of such a project. An
AFREF mail list has been established by the IGS to facilitate
discussion. You may view the correspondences and other information at:
http://igscb.jpl.nasa.gov/mail/afref/afref.html, as well as
instructions to subscribe.
Looking forward to your positive reply, and with best regards,
Claude Boucher
Chair, IAG Commission X, Global and Regional Networks
Head, International Terrestrial Reference Frame, IERS
IERS Representative to IGS Governing Board
Ruth E. Neilan
Director, International GPS Service Central Bureau
Member, Federation of Astronomical and Geophysical Data Services
Reference Web Sites:
IAG: http://www.gfy.ku.dk/~iag
IAG Commission X: http://lareg.ensg.ign.fr/GRGN/
IGS: http://igscb.jpl.nasa.gov
IERS: http://www.iers.org/
ITRF: http://lareg.ensg.ign.fr/ITRF/
FAGS: http://www.kms.dk/fags/
SIRGAS:
http://www.dgfi.badw-muenchen.de/gps/sirgas.html,
http://dgfi.badw-muenchen.de/dgfi/SIRGAS/sirgas.html
EUREF: http://homepage.oma.be/euref/
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IGS 2001 DIRECTORY
INFORMATION UPDATE FORM
Add or update your address electronically at any time, fill in the
information below and email back to:
directory-changes at igscb.jpl.nasa.gov
Please fill in the Subject heading with:
Directory Update - AREF Interest
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IGS Central Bureau
Jet Propulsion Laboratory, MS 238-540
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Ruth E. Neilan Telephone: (818)-354-8330
Director, IGS Central Bureau FAX: (818)-393-6686
Jet Propulsion Laboratory E-mail (IGS): igscb at igscb.jpl.nasa.gov
MS 238-540 E-mail: ruth.neilan at jpl.nasa.gov
4800 Oak Grove Drive
Pasadena, CA 91109
IGS Secretary: Mary Ann Hall Tel: 818-354-2077,
E-mail: MaryAnn.C.Hall at jpl.nasa.gov
IGS Information System: http://igscb.jpl.nasa.gov/
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