[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/



==========================================================================
                       IGS 2001 DIRECTORY
                      INFORMATION UPDATE FORM

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       Directory Update - AREF Interest

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IGS Central Bureau
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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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