H - IBGE

Transcription

H - IBGE

IAG
PAIGH
GEOCENTRIC REFERENCE SYSTEM
FOR THE AMERICAS
SIRGAS
NEWSLETTER # 7
December 2002
NIMA
IAG
PAIGH
NIMA
TABLE OF CONTENTS
EDITORIAL
MINUTES OF THE COMMITTEE MEETING, HELD ON OCTOBER 21 AND
22, 2002, IN SANTIAGO, CHILE
ANNEXES TO THE MINUTES
I: STATUS ON THE INTEGRATION OF THE SOUTH AMERICAN COUNTRIES
TO SIRGAS (WG II “GEOCENTRIC DATUM”)
II: PRESENTATION OF THE SIRGAS 2000 GPS CAMPAIGN RESULTS
III: ITRFYY AND ITS GEODETIC APPLICATION, BY MUNEENDRA KUMAR
PRESENTATIONS OF THE WG III “VERTICAL DATUM”
IV:
V:
INTRODUCTION
URGENT NEED OF A MODERN VERTICAL REFERENCE
SYSTEM
VI:
COMPUTATION OF GEOPOTENTIAL NUMBERS AND
PHYSICAL HEIGHTS
VII: REFERENCE SURFACE: CONSIDERATIONS REGARDING W0
VIII: FUTURE ACTIVITIES
IX: STATUTE OF THE SIRGAS PROJECT
X: LIST OF THE SANTIAGO MEETING ATTENDEES
XI: PICTURES OF THE MEETING
SIRGAS Project
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EDITORIAL
I am glad to introduce to readers the seventh edition of the SIRGAS Newsletter. This edition
integrally covers the last project meeting, held on October 21 and 22, in Santiago, Chile.
During this meeting, important discussions and resolutions were taken, which are described in
this newsletter, with emphasis to those related to the results of the SIRGAS 2000 GPS
campaign and to the new project statute.
I would like to take this opportunity to wish readers, colleagues of the SIRGAS community
and their families a Merry Christmas and a peaceful, healthy and successful New Year.
Luiz Paulo Souto Fortes
President of the SIRGAS Committee
SIRGAS Project
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MINUTES OF THE COMMITTEE MEETING, HELD ON OCTOBER 21 AND 22,
2002, DURING THE VII INTERNATIONAL CONGRESS OF EARTH SCIENCES, IN
SANTIAGO, CHILE
October 21st
1. Opening (L. Fortes, President of the Committee)
The president of the Committee highlighted the financial support given by the International
Association of Geodesy (IAG), decisive for holding the meeting. The Pan-American
Institute of Geography and History (PAIGH), which had approved funds for the project in
2002, could not honor this commitment due to financial difficulties that it is currently facing.
Therefore IAG responded to our last minute request, enabling the attendance of eight
participants of seven countries of South America, which was decisive for the success of the
meeting.
2. Status on the integration of the South American countries to SIRGAS (R. Barriga,
President of the WG II) (Annex I)
3. Presentation of the SIRGAS 2000 GPS campaign results by the processing centers
3.1 IBGE (S. Costa) (Annex II)
3.2 DGFI (K. Kanniuth)
The coordinates obtained in the individual solutions of each processing center (DGFI with
Bernese, DGFI with GIPSY and IBGE with Bernese) shown a consistency between each
other of about 5 mm in the horizontal components and 7.5 mm in the vertical component.
Resolution: The SIRGAS Committee decided that the final solution of the SIRGAS
2000 GPS campaign will be generated by the combination of three solutions: DGFI´s,
using the Bernese software; DGFI´s, using the GIPSY software; and IBGE´s, using
the Bernese software.
4. Combination of the processing centers´ results (H. Drewes/K. Kanniuth/S. Costa)
4.1 Combination strategy and connection to ITRF2000
M. Kumar, from NIMA, presented the following issue: the ITRF solutions are generated
using the tide-free system, which is not realistic and contradicts the IAG Resolution 16 of
1983 (Annex III)
Resolution: To keep using the tide-free system in the SIRGAS 2000 results and to
formally suggest to IAG to manage with the International Earth Rotation Service
(IERS) the solution of this issue.
SIRGAS Project
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4.2 Determination of velocities
According to H. Drewes, it is not enough to consider the results of the SIRGAS 1995 and
2000 campaigns for the determination of the SIRGAS stations velocities.
Resolution: The SIRGAS Committee approves H. Drewes´ proposal of considering
the observations of permanent GPS stations and of geodynamic campaigns, in
addition to the results of the SIRGAS 1995 and 2000 campaigns, for the
determination of the velocity field of the South American continent.
4.3 Final results (coordinates and velocities)
Resolution: The SIRGAS Committee accepts in advance as official the final
combined results of the SIRGAS 2000 GPS campaign, to be generated by the
processing centers in near future.
Resolution: The SIRGAS Committee defines the date of December 20, 2002, as the
deadline for the processing centers to release the final combined results of the
SIRGAS 2000 GPS campaign.
Resolution: The SIRGAS Committee defines the date of March 28, 2003, as the
deadline for DGFI to release the results of the velocity field for the South American
continent.
Resolution: The procedures to generate the official results of the SIRGAS 2000 GPS
campaign will be described in a final report, similarly to that released during the
IAG Scientific Assembly, held in Rio de Janeiro, in 1997.
Resolution: The SIRGAS Committee proposes to include in the SIRGAS 2000 GPS
campaign final report a special acknowledgment to the processing centers – DGFI
and IBGE – by the enormous efforts carried out and by the excellence of the results
obtained.
5. Use of the SIRGAS 2000 final results (H. Drewes, Representative of IAG)
Resolution: The SIRGAS Committee proposes to include in the SIRGAS 2000 GPS
campaign final report detailed instructions about how to use the campaign final
results.
It was recommended that, for countries that have not adopted yet SIRGAS 1995 as
reference system, they should adopt the system based on the SIRGAS 2000 results,
reference epoch 2000.4.
SIRGAS Project
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6. Presentation and start of discussion of the new statute proposal (C. Brunini, Substitute
Representative of Argentina)
October 22nd
7. Presentations of the Working Group III “Vertical Datum” (L. Sanchez, President of
WG III, and H. Drewes, Representative of IAG)
7.1 Introduction (Annex IV)
7.2 Urgent need of a modern vertical reference system (Annex V)
7.3 Computation of geopotential numbers and physical heights (Annex VI)
7.4 Reference surface: considerations regarding W0 (Annex VII)
7.5 Future activities (Annex VIII), recommending to countries:
•
•
•
•
•
•
•
Geodetic leveling of the SIRGAS2000 stations
Connection of leveling networks between neighboring countries
Identification and typing of all leveling lines that connect SIRGAS2000 stations
Typing of the national leveling networks
Identification of the network nodes
UNIFIED determination of the quasi-geoid
Determination of the sea surface topography (SSTop) (GPS positioning of tide
gauges)
The WG III president offered support to the member countries of the SIRGAS Committee
regarding the computation of geopotential numbers and help with parallel tasks. It is
emphasized that the height differences to be used in computations are the observed ones,
WITHOUT any error distribution or adjustment.
8. Continuation of the discussion on the new statute proposal (L. Fortes and C. Brunini)
Resolution: The SIRGAS Committee approves the new project Statute,
corresponding to the version originally proposed by the representation of Argentina,
with the modifications discussed during the meeting in Santiago del Chile.
With the approval of the Statute (Annex IX), the substitute representative of Argentina in
the Committee, Claudio Brunini, proposed the names of Luiz Paulo Souto Fortes, from
IBGE/Brazil, and Eduardo Andrés Lauría, from IGM/Argentina, respectively for president
and vice-president of the project for the next term (2003-2007). The current president of
the SIRGAS Committee will contact all countries embraced by the project in order to
confirm the names of the representatives in the Committee and, consequently, to define
the necessary quorum for electing the new project authorities. This election will be carried
out by electronic mail and the elected authorities will be installed in office in July 2003, at
the General Assembly of the International Association of Geodesy.
SIRGAS Project
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9. Closing (L. Fortes)
Resolution: The SIRGAS Committee acknowledges the Instituto Geográfico Militar
of Chile for the excellent organization of the meeting and for the support to the
Committee members.
10. List of attendees (Annex X)
11. Pictures of the meeting (Annex XI)
SIRGAS Project
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ANNEX I
STATUS ON THE INTEGRATION OF THE SOUTH AMERICAN COUNTRIES TO
SIRGAS (WG II “GEOCENTRIC DATUM”)
(included in the complete version of this Newsletter, available at
http://www1.ibge.gov.br/home/geografia/geodesico/sirgas/principal.htm)
GRUPO DE TRABAJO II
DATUM GEOCENTRICO
TCL. R. Barriga V.
email : rbarriga@igm.cl
GRUPO DE TRABAJO II
“DATUM GEOCENTRICO”
MISION :
Establecer un Datum Geocéntrico mediante la
extensión de la Red GPS SIRGAS a través de
la integración de las “Redes Geodésicas” de
cada uno de los países sudamericanos participantes en el Proyecto.
“SITUACION INDIVIDUAL DE CADA PAIS”
ARGENTINA
RESPONSABLES
: Claudio Brunini, Juan Moirano
U. Nac. De la Plata.
Rubén Rodríguez
Eduardo Lauría, Instituto Geográfico Militar.
MEDICIONES DE TERRENO
: 136 estaciones Red POSGAR 98
109 puntos en común con POSGAR 94
PROCES. DE LOS DATOS
: Universidad Nacional de la Plata - DGFI.
Software BERNESE 3.5
AVANCE
: Recientemente el Subcomité de Geodesia ha
recomendado el uso del nuevo marco de
referencia POSGAR 98 para las aplicaciones
geodésicas de alta precisión que se desarrollen
en el futuro, aunque mantendrá por un tiempo
más la vigencia de POSGAR 94.
POSGAR 98, época 1995.4
CONTRIBUCION A SIRGAS 2000 : 20 estaciones.
RED DE ARGENTINA
BOLIVIA
“SIN ANTECEDENTES ACTUALES”
RESPONSABLES
: Instituto Geográfico Militar
: Existen 2 Redes de control GPS
- Red geodésica Fundamental clase A
- Red Minera clase B.
: Instituto Geográfico Militar - UNLP
Software BERNESE.
.
ECUADOR
RESPONSABLES
: Departamento de Geodesia del instituto
Geográfico Militar
: 135 estaciones medidas durante 1994, 1996
y 1998.
: En DGFI, Munich, Software BERNESE 4.0.
AVANCE
: Obtención de coordenadas enlazadas a
SIRGAS, época 1995.4.
PUNTOS AMBOS SISTEMAS
: 42 puntos en común entre PSAD56 y
SIRGAS para la determinación de parámetros locales de transformación...
RED DEL ECUADOR
BRASIL
RESPONSABLES
: Sonia María Alves Costa - IBGE
Instituto Brasileiro de Geografía y Estadística.
CONTRIBUCION A SIRGAS
: 22 estaciones SIRGAS, 14 son de la Red de
Monitoreo Contínuo.
: IBGE, Software BERNESE 4.0.
AVANCE
: En Octubre del año 2000 el IBGE organizó y
coordinó el primer Seminario para visualizar
la adopción de el nuevo Marco de Referencia
Geodésico.
En el año 2005, Brasil pretende adoptar el
SIRGAS oficialmente.
RED DEL BRASIL
5
Rede Nacional GPS
ano 2002
0
Fortaleza
Manaus
-5
Imperatriz
Recife
Crato
-10
BomJesus
-15
Cuiaba
Salvador
Brasília
-20
Viçosa
P.Prudente
R.Janeiro
-25
Curitiba
GPS
SIRGAS/RBMC
-30
Sta. Maria
Porto Alegre
-70
-65
-60
-55
-50
-45
-40
-35
-30
CHILE
RESPONSABLES
: Instituto Geográfico Militar.
: 260 puntos Nueva Red Geodésica Nacional.
133 puntos conectados a la antigua Red.
: Instituto Geográfico Militar
AVANCE
: Coordenadas preliminares ITRF 2000, a la
espera de ajuste final a SIRGAS 2000.
Se estima que en el año 2005 se adoptará
oficialmente SIRGAS en Chile.
CONTRIBUCION A SIRGAS 2000 : 20 estaciones, incluyendo 8 estaciones GPS
permanentes y 5 mareógrafos.
RED CHILENA
COLOMBIA
RESPONSABLES
: Laura Sánchez
Instituto Geográfico Agustín Codazzi.
: La Red MAGNA consta de 60 estaciones GPS
de las cuales 16 corresponden a la Red CASA
(Red Geodinámica para Centro y Sur
de América).
: I. G. Agustín Codazzi - DGFI.
AVANCE
: La Red MAGNA y en consecuencia SIRGAS
fue adoptado como sistema oficial en
Colombia desde 1998.
Se están definiendo los estándares de geoposicionamiento a nivel nacional, dentro de
la normativa ISO9001.
RED DE COLOMBIA
13°
13.40°
PTBOL
12.60°
12°
13.38°
12.58°
NAZAR
13.36°
RIOHA
12.56°
13.34°
SMART
BQUIL
12.54°
11°
SANAN
13.32°
81.41°
81.39°
81.37°
81.35°
12.52°
SAN ANDRES, PROVIDENCIA Y
SANTA CATALINA
12.50°
10°
12.48°
81.75°
81.73°
81.71°
MAICA
VALLED
CARTA
81.69°
BOSCO
PLATO
COROZ
9°
MOMPO SROQU
MONTE
8°
TIBU
AGUAC
TURBO
CAUCA
7°
CUCUT
BUCAR
YARUM
CRNOR
RIONE
QUIBD
GUARI
YOPAL
BOGOT
OROCU
IBAGE
TULUA
MALPELO
PTCAR
TUNJA
MANIZ
5°
4°
ARAUC
PTBER
SOLAN
6°
SARAV
VILLA
BTURA
PTINI
CALI
3°
BACOM
NEIVA
GUAPI
2°
POPAY
SFELI
TUMAC
FLORE
MITU
PASTO
1°
SJGUA
MOCOA
IPIAL
0°
PTLEG
ARARA
1°
PEDRE
CHORR
2°
3°
4°
1994
1994 - 1995
1995
1994 - 1997
1997
1994 - 1995 - 1997
LETIC
5°
80°
79°
78°
77°
76°
75°
74°
73°
72°
71°
70°
69°
68°
67°
66°
PARAGUAY
RESPONSABLES
: Servicio Geográfico Militar
: 165 puntos medidos de la Red Geodésica
primaria en 1992.
: Servicio Geográfico Militar y por el NIMA.
CONTRIBUCION A SIRGAS 2000 : 1 Estación.
PERU
RESPONSABLES
: Instituto Geográfico Nacional
: 165 puntos medidos de la Red Geodésica
primaria en 1992.
: Servicio Geográfico Militar y por el NIMA.
URUGUAY
RESPONSABLES
: Servicio Geográfico Nacional y el
Instituto de Agrimensura.
VENEZUELA
RESPONSABLES
: José Napoleón Hernández
Instituto Geográfico de Venezuela Simón Bolivar
: 156 estaciones entre 1995 y 2000.
: Software BERNESE
AVANCE
: Venezuela posee 210 vértices integrados a
SIRGAS, disponibles y publicados. Así mismo
se encuentran 500 vértices totalmente calculados, en fase de edición de descripciones,
accesos y monografías.
Venezuela oficialmente ha adoptado a SIRGAS
como nuevo Sistema de Referencia.
RED DE VENEZUELA
GRUPO DE TRABAJO II
DATUM GEOCENTRICO
TCL. R. Barriga V.
email : rbarriga@igm.cl
IAG
PAIGH
ANNEX II
PRESENTATION OF THE SIRGAS 2000 GPS CAMPAIGN RESULTS
NIMA
RESULTS OF THE SIRGAS 2000 GPS
CAMPAIGN
Klaus Kaniuth - Deutsches Geodatisches
Forschungsinstitut - DGFI
Sonia Costa - Brazilian Institute of Geography and
Statistics - IBGE
International Symposium of the IAG
Recent Crustal Deformation in South America and Surrounding
Area, october, 2002
RESULTS OF THE SIRGAS 2000 GPS CAMPAIGN
Goals of SIRGAS2000 campaign
¾ Maintenance of SIRGAS reference frame;
¾ Define a unique height reference system for
the Americas.
2
Selection criteria of stations
¾ Tide gauges, which define the vertical datum of
the leveling networks in each country;
¾ Other
tide
gauges
(countries
with
long
extension of coast);
¾ Stations of leveling networks at the borders
between neighboring countries;
¾ Stations participating of SIRGAS95 network.
3
Campaign Specifications and
Equipment
¾The data on each station was organized in 24 hours
period and converted to RINEX format;
¾ Data collection rate was 15 and 30 (IGS and NGS) sec. ;
¾ Double frequencies receivers preferably with choke ring
antenna or receivers without choke ring antenna, that
ones recognized by IGS;
¾Station
information's:
sessions,
antenna
station
height
name,
observation
(slant/vertical)
and
antenna/receiver type (IGS identification).
4
Processing Information's
¾ Orbits and ERP: Combined IGS (SP3 files);
¾ Coordinates of the reference stations : ITRF97, epoch
2000.3;
¾Antenna phase center offset and variation: Information
obtained at IGS and NGS;
¾Antenna heights were corrected to ARP
(Antenna
Reference Point).
¾Software: Bernese , version 4.2
5
Processing Strategies - IBGE
Solutions
Mode
Observations
Strategy forming
baselines
Sampling rate
Elevation cut off angle
Elevation weighting
Troposphere model (A
PRIORI)
Trop. zenith delay
Mapping function
Ionosfere model
Ambiguity resolution
Ocean Loading
Reference Stations
Options
Daily sessions
double differences, observable L3 (ionosphere
free, linear combination of L1 and L2)
OBS-MAX
30 sec.
10 degrees
Cos(z)
Not applied
Every 2 hours (12 corrections)
Niell (dry component)
Not applied
QIF (Quasi Ionosfere Free) + GIMs\CODE maps
Not applied
AREQ, AMC2, ALBH, AOML, BRAZ, CRO1,
FORT, LPGS, OHIG, KOUR, SANT, WES2,
CORD, JAMA and UNSA
6
Combination
of Solutions
/ IBGE
¾ Divided in 9
blocks, with about
22 stations each;
¾ 3 IGS stations
make the link
between blocks;
¾ Final daily
solutions were
saved as removable
constraints
7
Link Stations between blocks
N
WES2
AMC2
ALBH
N1
WES2
AMC2
ALBH
BRMU
AOML
INEG
N2
AOML
INEG
BRMU
JAMA
CRO1
ESTI
C
JAMA
CRO1
ESTI
CART
FORT
KOUR
S
CART
FORT
KOUR
BOGA
IMPZ
BRAZ
S1
BOGA
IMPZ
BRAZ
AREQ
ZAMO
UNSA
S2
BRAZ
ZAMO
UNSA
LPGS
CHAM
CORU
S3
UNSA
LPGS
CHAM
CORU
SANT
CORD
S4
LPGS
SANT
CORD
8
Network
Configuration
and Blocks
Division
- IBGE -
STATIONS PROBLEMS AND CHANGES
–
–
–
–
–
–
–
–
UCOR (Argentina) and NPAC (Guatemala) were not used in
processing.
CART (Colombia) is a different station from campaign 1995, but
has the same identification for SIRGAS2000.
BATL (Ecuador) was identified as GALA (Ecuador) in campaign
1995. Consequently, GALA in campaign 2000 (IGS station) is a
different station from campaign 1995.
MANU (Brazil) station was identified as MANA in campaign 1995.
L10B (Argentina) was identified as LO10 in campaign 1995.
CACH (Brazil) station from campaign 1995 was destroyed and
changed to CAC1.
BOGT (Colombia) station in 1995 campaign, was changed to
BOGA.
Stations YACA (Uruguay), ASUN (Paraguay), were not occupied in
SIRGAS 2000 campaign.
10
DATA PROBLEMS
VIMS (U.S.)/day 133, YBHB
– Too many cycles slips:
(U.S.)/day 134, TEGU (Honduras)/ day131, CHIQ (Bolivia)/
days 131-132.
– Few quantity of data: KAMA (Venezuela)/day132 (4 hours of
data), ARIC/day 135 (1:30 of data), LOTE (Argentina)/day 136
one hour of data), RIOP (Ecuador)/day 134 (some minutes of
data), NPRI (U.S.)/day 132 (less than 6 hours of data), AMC2
(U.S.)/day 137 (less than 6 hours of data), CA00/day 137.
– Data from wrong date: MERI (Mexico)/day 138 (data from
1980), CHI3 (Mexico)/day 135, OAXA (Mexico)/day 135, RBLS
(Argentina)/day 139.
– Data excluded because of observations problems: ANTF
(Chile)/days 136, 137, 138, 139 and 140.
11
Results
¾ Preliminary combination: ADDNEQ
¾ removable constraints: CRO1, KOUR, FORT, ALBH,
WES2, BRAZ, AREQ, LPGS, SANT, OHIG and CORD.
¾ Stations excluded from final results: UCOR, NPAC and
ANTO.
¾ Number of stations processed = 182
¾Stations with less than 5 days of solutions: CHAJ (3
days), JUNQ (3 days), LOTE (4 days), ELEN (2 day) and
RIOP (3 days).
¾ Checking accuracy with ITRF2000:
Stations, which have residuals higher than 20 mm are:
GALA, CRO1, INEG, SIO3.
12
-20
-60
-40
STATIONS
60
40
YELL
IGM0
20
HOLB
GODE
GALA
GAL1
FORT
FLIN
EISL
DUBO
DRAO
CUIB
CRO1
CORD
CHUR
CHA1
BRMU
BRAZ
BOMJ
ASHV
AREQ
AOML
AMC2
ALGO
30
WILL
WHIT
WES2
VIMS
VICO
VBCA
USNO
USNA
UEPP
STJO
SOL1
SIO3
-30
SCH2
SANT
RIOP
RIOG
PUR3
PARA
OHIG
MANU
LPGS
KOUR
JAMA
INEG
MM
ALBH
-10
IMPZ
MM
Accuracy of solution / IBGE
ITRF2000 RESIDUALS
NORTH
EAST
UP
10
0
-20
STATIONS
ITRF2000 RESIDUALS
NORTH
EAST
UP
20
0
Consistency of daily solutions /
IBGE
–The stations, which have up component RMS higher
than 20 mm are: IMPZ and TALA
–EISL station presented higher RMS in the internal
solution
14
Consistency of Block solutions
milimeter
UNWEIGHTED RM S RESIDUALS - NORTH COM PONENT
14
SIRGASN
12
SIRGASN1
10
SIRGASN2
8
SIRGASC
6
SIRGASS
4
SIRGASS1
2
SIRGASS2
0
DAYS 131
132
133
134
135
136
137
138
139
140
SIRGASS3
SIRGASS4
milimeters
UNWEIGHTED RMS RESIDUALS - EAST COMPONENT
14
12
10
8
6
4
2
0
DAYS131
SIRGASN
SIRGASN1
SIRGASN2
SIRGASC
SIRGASS
SIRGASS1
SIRGASS2
132
133
134
135
136
137
138
139
140
SIRGASS3
SIRGASS4
milimeters
UNWEIGHTED RMS RESIDUALS - UP COMPONENT
18
16
14
SIRGASN
SIRGASN1
12
10
8
6
SIRGASN2
4
2
0
SIRGASS1
DAYS 131
SIRGASC
SIRGASS
SIRGASS2
132
133
134
135
136
137
138
139
140
SIRGASS3
15
SIRGASS4
Consistency of Block solutions
SIRGASN
WEIGHTED RM S RESIDUALS - NORTH COM PONENT
SIRGASN1
milimeter
14
12
10
8
6
4
2
0
milimeter
DAYS
SIRGASN2
SIRGASC
SIRGASS
SIRGASS1
SIRGASS2
SIRGASS3
131
132
134
135
136
137
138
139
140
SIRGASN1
SIRGASN2
SIRGASC
SIRGASS
SIRGASS1
SIRGASS2
SIRGASS3
131
132
133
134
135
136
137
138
139
140
milimeters
WEIGHTED RMS RESIDUALS - UP COMPONENT
14
12
10
8
6
4
2
0
DAYS
SIRGASS4
SIRGASN
WEIGHTED RMS RESIDUALS - EAST COMPONENT
14
12
10
8
6
4
2
0
DAYS
133
131
132
133
134
135
136
137
138
139
140
SIRGASS4
SIRGASN
SIRGASN1
SIRGASN2
SIRGASC
SIRGASS
SIRGASS1
SIRGASS2
SIRGASS3
SIRGASS4
16
IAG
PAIGH
ANNEX III
ITRFYY AND ITS GEODETIC APPLICATION
BY MUNEENDRA KUMAR
NIMA
ITRFyy AND ITS GEODETIC APPLICATION
By
Muneendra Kumar
National Imagery and Mapping Agency
Bethesda MD 20816-5003 (USA)
Abstract
The International Terrestrial Reference Frame (ITRF) is a realization
of the International Terrestrial Reference System (ITRS). Since its
first realization in 1988, there have been many variations and additions
in data types and changes in computations of ITRF. Between ITRF88 and
ITRF97, the reference epochs have also changed three times. Many
technical notes from the International Earth Rotation Service (IERS) are
available. These notes explain and provide in great details all the
technical complexities of different realizations, which have been update
every year between 1988 and 1994. After 1994, the ITRF 96 and 97 are the
two latest solutions.
This paper intends to present and clarify the technical
interpretation of the ITRF realization and its definition for the
practical geodesists who want to update the geodetic infrastructure of a
nation, region, continent, or for the world. The attempt here is to
include significant details and explanations to provide a clear and
consistent interpretation.
1. INTRODUCTION
International Earth Rotation Service (IERS), since it’s founding in
1988, has been updating ITRS with its realizations as ITRF. First
solution was ITRF88, which then was followed yearly by ITRF89, 90, 91,
92, 93, and 94. After this, we got two more solutions, viz., ITRF96 and
ITRF97.
ITRF realization consists in a set of station Cartesian coordinates,
a velocity field, and a full variance-covariance matrix (Silard et al,
1998). The direction of the IERS Reference Pole (IRP) and Reference
Meridian (IRM) corresponds to the Bureau International de L’Heure (BIH)
Conventional Terrestrial System (CTS) Pole and Zero Meridian (McCarthy,
1996).
Between 1988 and 1993, ITRFyy (where “yy” corresponds to the year in
which it was realized) solution was obtained by a combination of all
data submitted to the beginning of yy+1 (Boucher et al, 1997). Here, the
reference epoch was 1988.0. The ITRF94 was then defined to the reference
epoch 1993.0.
Then, the reference frame definition (origin, scale, orientation, and
time evolution) was achieved in such a way that ITRF96 is in the same
system as ITRF94 (Boucher et al, 1997). This was followed by a combined
solution for ITRF96 and ITRF97 with 1997.0 as reference epoch.
This paper provides and clarifies the technical details concerning
the different ITRFs and their reference epochs with the each periodic
IERS solution. A suggested approach is also included for geodetic use
when updating national, regional, continental, and/or global geodetic
system(s) or datum(s).
Published in the Proceedings of the IAG 2001 Scientific Assembly, 2-7 September 2001, Budapest, Hungary
2.
INTERNATIONAL TERRESTRIAL REFERENCE FRAME (ITRF)
ITRF is a realization of the International Terrestrial Reference
System (ITRS). The orientation of its axes is consistent with the Bureau de
L’Heure (BIH) Conventional Terrestrial System (CTS) at the epoch 1984.0, in
accordance with the resolution of the International Union of Geodesy and
Geophysics (IUGG) and International Astronomical Union (IAU).
The orientation of the system is such that it has no residual
rotational horizontal velocity relative to the Earth’s crust. The
construction of the ITRF is based on the combination of sets of station
coordinates and velocities derived from observations from Very Long
Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), and Lunar
Laser Ranging (LLR). Data from Global Positioning System (GPS) was
introduced in 1991 and from Doppler Orbitography and Radio-positioning
Integrated by Satellite (DORIS) in 1994.
ITRFyy represents a solution, which is based on the data sets that
are available till the end of year “yy” and is performed in the year
“yy+1”. From the first ITRF88 the solutions are available for 89, 90, 91,
92, 93, 94, 96, 97, and a combined solution for 96 and 97.
3.
ITRF COMPUTATIONS
The procedure is in sequential steps.
(1)
First step involves a reduction of coordinates for the
participating stations to a common reference epoch t0
using their respective velocity models. These velocity
models are either based on fixed tectonic plate motion or
estimated velocity fields.
The computations (XS, XS’)t0 are done separately for each
system “S”, e.g., VLBI.
(2)
Second step involves a least-squares estimation at the
reference epoch “t0” the coordinates and velocities for
the ITRFyy of all the stations from all the systems,
e.g., VLBI, SLR, LLR, GPS, and DORIS. The model used in
the “combination” solution is based on Euclidian
similarity of seven parameters:
XS
S
Y
S
Z
=
X
T1S
Y
S
Z
+
t0
T2
T3
DS
+
S
R3
R2
S
-R3S
S
X
S
Y
S
R1
S
S
D
R1
R2S
D
Z
(1)
t0
where X,Y,Z are the coordinates of a station at reference
epoch t0 in the ITRFyy, T1S, T2S, T3S, DS, R1S, R2S, R3S are
respectively the three translations, scale factor, and three
rotations between the ITRFyy and individual “S” solutions.
(3)
The local geodetic survey ties, with their standard
deviations, are used to tie the stations of the different
systems.
4.
ITRF EPOCHS
From the first ITRF88, the reference epochs used to define different
ITRF solutions (Altamimi, 2000) are:
ITRF88 to ITRF93
-
1988.0
ITRF94
-
1993.0
ITRF96
-
1993.0
ITRF96 and ITRF97
-
1997.0
ITRF00
-
1997.0
Here, we can interpret that ITRF 89 to ITRF93 represent the
realization of ITRF88 with additional data sets in each subsequent
solution. Thus, in real sense, each of the solutions for the years 1988 to
1993 only realized the same ITRF.
It is important to note that the combined solution for the ITRF96 and
ITRF97 was obtained by combining positions and velocities simultaneously.
This procedure allowed the use of full variance-covariance matrices of the
individual VLBI, SLR, GPS, and DORIS data solutions. This will allow users
to propagate the 1997.0 positions to any desired epoch. Thus, this approach
also replaced the old ITRF96 as a separate realization.
5.
ITRF DEFINITION
Coordinates are defined in a conventional “tide-free” system
(APPENDIX
1) where effects of all tidal have been removed. To achieve this, the
Equation 6 (Pp. 57, IERS Tech Note 21, 1996) is used.
6.
ITRF ORIENTATION AND SCALE
(1)
The orientation is defined by adopting IERS Earth Orientation
Parameters (ERP) at a “reference” epoch (See Section 3).
(2)
The orientation of the IERS Reference Pole (IRP) and Reference
Meridian (IRM) were initially given by the BIH Terrestrial
System (BTS) 1984.0 (McCarthy, 1996). Subsequently, the IRP and
IRM are consistent with the “corresponding” directions of the
BTS within 0.005”. Thus, the corresponding BTS for the ITRF
solutions from 1988 to 1993 (Section 4) will then be:
ITRF88 to ITRF93
-
BTS 1988.0
Since BIH was replaced by IERS from 1988, the orientations for
ITRF94, ITRF96, and ITRF97 followed an independent definition.
According to Montag (1997), the IRP and IRM were defined by
IERS on the basis of the Conventional International Origin
(CIO). However, it is not clear which CIO would have been used.
(3)
The scale is obtained by relativistic modeling and is
consistent with the Geocentric Coordinate Time (TCG) for a
geocentric local frame (Chapter 11, IERS Tech. Note 21, 1996).
(4)
The unit is meter (SI).
The time evolution of the orientation is maintained by using a
no-net- rotation condition with regards to the horizontal
tectonic motions over the whole Earth.
7.
MOVEMENT OF THE GEOCENTER
Recent analysis of SLR and other satellite data has shown that the
coordinates of stations connected to the solid Earth, as realized by the
ITRF, show variations as compared with the ITRF, which is assumed to be
fixed to the rigid Easrth’s crust (Montag, 1997). Thus, the origin of the
ITRF is defined such that the time-dependent translation vector T (from the
ITRF origin to the instantaneous center of mass of the Earth) is minimum
(Montag, 1997).
8.
GEODETIC APPLICATION
A. Important Considerations (McCarthy, 1996) -
a. ITRF coordinates are realized in the tide-free system and it is
important to note that this system is not realistic and the crust can not
be observed.
b. Alternatively, in the zero-tide system, the crust corresponds
to the realistic time average which varies because of the action of lunisolar tides.
c. The ITRF coordinates (Section 8.A.a. above) contradicts the IAG
Resolution 16, adopted at The 1983 General Assembly (APPENDIX 2).
B. Recommendation The following steps relate to a 10-day GPS campaign scenario which is
observed from 25 June to 5 July 2001, with mid-epoch of 2001.5.
a.
Select the IGS stations, which are to be used as constraints to
define the intended geodetic system.
b.
Using the “latest” available ITRF coordinates and velocities,
viz., ITRF00 with reference epoch 1997.0, propagate coordinates
of the stations to the mid-epoch 2001.5.
c.
To be consistent with the IAG Resolution 16, 1983 (APPENDIX 2),
compute the IGS station coordinates to the zero-tide
environment.
d.
Adjust the network using the propagated and restored
coordinates with the zero-tide effects as constraints with
appropriate weights.
The reference frame of the geodetic system can be held fixed till the
next accuracy enhancement. It need not change with each new realization of
an ITRFyy. A reference epoch change would be optional but may not be
necessary.
References
Boucher, C. Altamimi, Z., and Sillard, P., 1998. “Results and Analysis of
the ITRF96”, IERS Technical Note 24, Central Bureau of IERS, Paris, France.
Boucher, C. Altamimi, Z., and Sillard, P., 1999. “The 1997 International
Terrestrial Reference Frame (ITRF97)”, 1999, IERS Technical Note 27,
Central Bureau of IERS, Paris, France.
Ekman, M., 1989. “Impacts of Geodetic Phenomena on Systems of Height and
Gravity”, Bull. Geod., 63.
McCarthy, D. D., 1992. “IERS Standards (1992)”, IERS Technical Note 13,
McCarthy, D.D., 1996. “IERS Conventions (1996)”, IERS Technical Note 21,
Montag, H., 1997. “Zur Definition and Uberwachung der Parameters des
International Terrestrial Reference Systems ITRF mit besonderer
Berucksichtigung der Variationen des Geozentrums”, Zeitschrift fur
Vermessungswesen (ZfV), vol. 123, No. 7. (English Translation, NIMA TC5480, 2000)
Rapp, R. H., 1989. “The Treatment of Permanent Tidal Effects in the
Analysis of Satellite Altimeter Data for Sea Surface Topography”, Ma,
Geod., 14.
APPENDIX 1
To account for the effect of the permanent tide, terrestrial
reference frames may be defined:
Zero-tide – Permanent or “zero frequency tide” is retained.
The crust corresponds to the realistic time average,
which varies with the luni-solar tides.
Tide-free – All effects of permanent tide are removed.
This is not realistic since the crust can not be
observed.
Mean-tide – This a “tide-free” system except the geoid is modeled
with permanent tide effects.
References
McCarthy, Dennis D., “IERS Technical Note 21”, 1996.
Ekman, M., 1989. “Impacts of Geodetic Phenomena on Systems of Height and
Gravity”, Bull. Geod., 63.
Rapp, R. H., 1989. “The Treatment of Permanent Tidal Effects in the
Analysis of Satellite Altimeter Data for Sea Surface Topography”, Ma,
Geod., 14.
Poutanen, M., Vermeer, M., and Mekinen, J., 1996. “The Permanent Tide in
GPS Positioning”, Journal. Of GEOD.
APPENDIX 2
IAG Resolution No. 16, 19831
The International Association of Geodesy (IAG),
recognizing the need for the uniform treatment of tidal corrections
to various geodetic quantities such as gravity and station positions, and
considering the reports of the Standard Earth Tide Committee and
S.S.G. 2.55,
recommends that :
1. the rigid Earth model be the Cartwright – Taylor - Edden
model with additional constants specified by the
International Centre for Earth Tides,
2. the elastic Earth model be that described by Wahr using the
1066 A model Earth of Gilbert and Dziewonski,
3. the indirect effect due the permanent yielding of the Earth
be not removed,
and
4. ocean loading effects be calculated using the tidal charts
and data produced by Schwiderski as working standards.
1 Text obtained from IAG.
IAG
PAIGH
ANNEX IV
PRESENTATIONS OF THE WG III “VERTICAL DATUM”:
INTRODUCTION
NIMA
GTIII-SIRGAS: Dátum Vertical
• Sep 1997: Adopción oficial de las coordenadas SIRGAS y creación del
GTIII-SIRGAS: Dátum vertical. Presidente: R. Luz
• Ago 1998: Taller de trabajo: consideraciones teóricas para la definición del
nuevo sistema vertical:
+ alturas elipsoidales
+ un tipo de alturas físicas
+ superfcies de referencia correspondientes
+ realización mediante un marco de referencia (h, C, N)
• Jul 1999: Documento técnico sobre los fundamentos teóricos del sistema
vertical, BIVAS/BIDAS, planificación campaña GPS mayo 2000
• May 2000: Campaña GPS: realización de la componente geométrica del nuevo
sistema vertical: 184 estaciones, 115 en América del Sur
• Feb 2001: “Sistema de referencia geocéntrico para las Américas“,
recomendación oficial para la adopción de alturas normales
• Sep 2001: Preprocesamiento de las campaña 2000.
Presidente GTIII-SIRGAS: Laura Sánchez
Santiago de Chile, Octubre 2002
Componentes del nuevo sistema vertical
1. Alturas:
Elipsoidales (componente geométrica)
Normales (componente física)
2. Superficies de referencia:
Elipsoide GRS80 (Elipsoidales)
Cuasigeoide (Normales)
3. Marco de referencia:
Estaciones SIRGAS95
Mareógrafos
estaciones fronterizas
H N= h - ζ
HN = C/γm
HN = Σdn + kN
nivel de referencia (W0)
nivel medio del mar
coordenadas SIRGAS
nivelación geométrica
valor de gravedad
4. Mantenimiento del sistema de referencia:
Cambios del marco de referencia a través del tiempo
Actividades recientes en los países de América del Sur
relacionadas con el GTIII-SIRGAS (I)
➤ Diagnóstico de los sistemas de alturas existentes
✔
✔
✔
✔
✔
✔
The vertical reference system in the Argentine Republic (Lauría, et al. 2001)
Brazilian first order levelling network (Luz, et al. 2001)
The vertical geodetic network in Chile (Maturana et al.2001)
Considerations of different height systems in Venezuela (Wildermann, et al. 2001)
Vertical height system in Colombia (Sánchez 2001)
Reportes al GTIII: Argentina, Brasil, Bolivia, Chile, Colombia, Ecuador, Perú, Uruguay
➤ Determinación de la componente geométrica (alturas elipsoidales)
✔ Procesamiento SIRGAS2000: Kaniuth (DGFI), Costa (IBGE)
➤ Superficies de referencia: Cuasi-geoide
✔Subcomisión de la IAG para la determinación del geoide en América del Sur
✔New results in the determination of the geoid model in Argentina (Pacino, et al. 2001)
✔Data collecting and processing for a quasi-geoid determination in Brazil
(Blitzkow, et al. 2001)
✔Improving a quasi-geoid model in Colombia (Martínez, et al, 2001)
✔The vertical datum and local geoid models in Uruguay (Subiza, et al. 2001)
✔Current status of geoid calculation in Venezuela (Hoyer, et al. 2001)
✔A reference suface for the unified height system in the northern part of South America
(Sánchez, 2001)
Actividades recientes en los países de América del Sur
relacionadas con el GTIII-SIRGAS (II)
➤ Topografía y variación de la superficie del mar
✔ Correlation between multi-mission altimeter time series and tide gauge registration
in the Caribbean sea (AcuEa, et al. 2001)
✔Monitoring tide gauges benchmarks in Argentina by GPS (Natali, et al. 2001)
✔Connecting sea level and height systems along the coast of South America
(AcuEa, et al. 2001)
✔Local effects in the Brazilian vertical datum (de Freitas, et al. 2001)
✔AcompaEamiento del dátum altimétrico Imbituba a través de las redes altimétrica y
mareográfica del sistema geodésico brasileEo (Luz et al. 2001)
✔Vertical crustal movement of tide gauges in Argentina (Natali, et al. 2002)
➤ Nivel del cuasi-geoide (W0)
✔Associated problems to link the South American vertical networks and possible
approaches to face them (de Freitas, et al. 2001)
✔Realisation of the Soth American reference system (Sánchez & Drewes 2002)
➤ Cálculo de números geopotenciales
✔Approach to the new vertical reference system for Colombia (Sánchez & Martínez 2001)
✔Comparisson of the classical and the modern vertical reference system in Colombia
(Sánchez & Drewes 2001)
✔Hacia una nueva referencia vertical en Argentina (Moirano et al. 2002)
GTIII-SIRGAS: Taller de trabajo, Santiago de Chile, octubre 2002
➨ Importancia de la definición de un
sistema vertical moderno de referencia
➨ Cálculo de número geopotenciales
➨ Comentarios sobre el nivel de la superficie de referencia
física: Cuasi-geoide
➨ Actividades inmediatas .... URGENTES!!!
IAG
PAIGH
ANNEX V
URGENT NEED OF A MODERN VERTICAL REFERENCE SYSTEM
NIMA
The Urgent Need of Modern Vertical Reference Systems
Status of classical height systems (1)
• Classical height reference systems shall refer to the geoid as an
equipotential surface of the Earth’s gravity field.
• They are connected to the mean sea level (MSL) during an
arbitrarily chosen epoch at a selected tide gauge.
• The mean sea level of a tide gauge does not refer to the geoid
- because of the geographic variations of sea level (SSTop).
Sea Surface
Topography
Around South
America
Bosch 2000
Status of Classical Height Systems (1)
- because of the geographic variations of sea level (SSTop)
- because of temporal variations of mean sea level
Variation of Tide
Gauge Records
Examples:
Mar del Plata (Arg.) -0,2 mm/a
Buenaventura (Col.) 6,1 mm/a
La Libertad (Ecu.)
-1,0 mm/a
La Guaira (Ven.)
2,5 mm/a
- because of the geographic variations of sea level (SSTop)
- because of temporal variations of mean sea level
Consequences
• All height systems referring to different tide gauges (i.e.,
national height systems) provide a different height level.
• Heights are extended from the tide gauges to the continental
interior by spirit levelling.
• Spirit levelling does not refer to the geoid, but it has to be
corrected for gravity effects.
Heights from Spirit Levelling
Orthometric Heights and Normal Heights
Orthometric heights:
H = (W0 - WP) / gm
Normal heights:
HN = (W0 - WP) / γm
gm can only be determined
using a hypothesis on the
gravity gradient dg/dH
γm can be computed from the
normal gravity field of the
reference ellipsoid (GRS80)
Modern Height Systems
• Nowadays heights are determined with modern geodetic
space techniques, e.g., GPS.
• The primary height system is geometrically defined by a
reference ellipsoid.
Ellipsoidal Heights
Combination of Modern Heights and Classical Heights
To transfer modern heights (h) to classical height systems they have to
be reduced because of geoid undulations (N) or height anomalies (ζ)
h
H=h-N
h
HN = h - ζ
This requires the determination of geoid or cuasigeoid, respectively.
Most global gravity field models refer more closely to the cuasigeoid
than to the geoid (because they do not reduce local gravity gradients).
Conclusion
• Height determination will be done in future primarily by GPS.
• To combine ellipsoidal heights from GPS with classical heights
from spirit levelling we have to reduce both of them to the same
height reference system.
• Reduction of ellipsoidal heights (from GPS) to normal heights is
possible without hypothesis and in a unique global reference
frame by height anomalies from global cuasigeoid computations.
• To apply “GPS levelling” correctly it is necessary to reduce all
national height systems from levelled heights to normal heights!
IAG
PAIGH
NIMA
ANNEX VI
COMPUTATION OF GEOPOTENTIAL NUMBERS AND PHYSICAL HEIGHTS
Cálculo de números geopotenciales
dn1 ≠ dn2
Supercie E
quipotencia
l
B
3
dn1
2
1
A
dn2
Línea de la plomada (dirección del vector de la gravedad)
W = W2
W = W1
Geoid
W = W0
p
C = W0 − W p = ∫ g ⋅ dn = ∑ g i ⋅ ∆ni
0
i
CB = (g A1 ⋅ ∆n A1 )+ (g12 ⋅ ∆n12 )+ (g 23 ⋅ ∆n23 )+ (g 3 B ⋅ ∆n3 B )
g A1
g A + g1
=
2
GTIII-SIRGAS Santiago de Chile, Octubre 2002
Información requerida:
☛ Diferencias de nivel medidas (errores sistemáticos)
☛ Distancia (en km) entre los puntos nivelados
☛ Año de nivelación
☛ Valores de gravedad real en cada punto de nivelación
Diferencias de nivel medidas (errores sistemáticos)
Refracción
ε =ε
R
ε
R
ε ≠ε
R
ε
V
ε
R
V
ε
V
V
Distancia (en km) entre los puntos nivelados
Error medio (Ponderación)
m∆n = 4 mm d [km ]
p∆n
1
1 / 16
= 2 =
m∆n
d [km ]
Año de nivelación
Nivelaciones en diferentes épocas
D
C
1985
1985
C
1950
A
1992
B
A
B
1950
E
D
8
197
1962
E
D
Cambios en los desniveles C
medidos entre los mismos puntos:
errores de observación?
movimiento vertical?
Reducción de las observaciones a una sóla época?
Valores de gravedad real en cada punto de nivelación
Disponibilidad de valores de gravedad
E
B
A
C
D
Interpolación de los valores de gravedad observada!!
Precisión requerida en la interpolación de gravedad
para el cálculo de números geopotenciales
C = ∑ g ∆n ⇒ mC2 = g 2 m∆2n + ∆n 2 mg2
Σ∆n [m]
10
20
30
40
50
70
100
200
500
1000
2000
4000
⇒ m∆n = ± 4 mm d [km ]
mg[mGal]
d = 1km
mg[mGal]
d = 2km
40
20
13
10
8
6
4
2
1
0,5
0,3
0,1
55
28
19
14
11
8
6
3
1,5
0,8
0,5
0,2
Recomendaciones referentes a la interpolación de gravedad
para el cálculo de números geopotenciales
⇒ La gravedad varía con la altura y con las masas
⇒ Anomalía de Bouguer!!
∆gBouguer = gobs + CAL + Cbouguer - γ
⇒
gobs = ∆gBouguer - CAL -CBouguer + γ
CAL = 0,3086 H
CBouguer = -2πGρ H ≈ - 0,1119 H
γ = Gravedad teórica sobre GRS80
⇒ Precisión de la latitud para el cálculo de γ:
Interpolación de gravedad: ~2” ≈ 60 m
Alturas normales:
~0,5”≈ 15 m
⇒ Altura de los puntos a interpolar:
H=
punto
∑ ∆n
mareógrafo
Actividades URGENTES relacionadas con el cálculo
de números geopotenciales
Digitación (formato digital) de las nivelaciones nacionales
→
→
→
→
→
→
nombre del punto
desnivel medido
distancia [km] entre ellos
año de observación
coordenadas geodésicas (latitud y longitud)
valor de gravedad observado o interpolado a
partir de Anomalía Simple de Bouguer
Actividades INMEDIATAS relacionadas con el cálculo
Identificación de los nodos de las redes de nivelación nacionales
Actividades RE-URGENTES relacionadas con el cálculo
Identificación y digitación de todas las líneas de nivelación que
conectan las estaciones SIRGAS2000:
(SIRGAS95, mareógrafos y estaciones fronterizas)
Y después de los números geopotenciales.....
Definición de los dátum clásicos:
Superficie del mar = Geoide
Imbituba
Buenaventura
C
ol
om
bi
a
Br
Geoide
as
il
H
h
Nivel medio del mar
N
Elipsoide
Y después de los números geopotenciales.....
Sistema vertical modeno:
Superficie del mar ≠ Geoide
Buenaventura
Imbituba
C
ol
om
bi
a
Br
NMM (1942 - 1963)
W0 Col
Geoide
SSTop (Col)
Ccol
as
il
Cbra
∆W
NMM (1949 - 1957)
SSTop (Bra)
W0 Bra
⇒ Cúal puede ser la referencia para ∆W?
⇒ Es necesario definir un W0?
Elipsoide
IAG
PAIGH
ANNEX VII
REFERENCE SURFACE: CONSIDERATIONS REGARDING W0
NIMA
The Realisation of the Height Reference Surface
- W0 Considerations • Earth gravity models, such as EGM96, provide a spherical
harmonic expansion of the gravity potential:
GM
W=
r
∞

1 + ∑
 l =1
l
 1 2 2
a
 
  (Clm cos mλ + S lm sin mλ ) Plm (cos θ ) + ω p
∑
m =0  r 
 2
l
• The radius r, for which to apply this expansion, may arbitrarily
be chosen, e.g., the semimajor axis a of a best-fitting ellipsoid.
• Therefore, the geoid is not unequivocally prescribed but has to
be defined by a certain value a, or equivalently by W0.
• After the definition of Listing (1873) the equipotential surface
W = W0 of the geoid coincides with the mean sea level. This is
not automatically realised by using an Earth gravity model.
General Procedure of W0 Determination
From satellite altimetry we get the three-dimensional position
of the sea surface. This surface differs from the geoid because
of sea surface topography (SSTop).
geoid
ellipsoid
sea surface
Geoid W0
Sea Surface WSS
ri
rk
SSTop
- We determine the gravity
potential WSS of all the sea
surface around the world
from a Earth gravity model.
- We compute the average
of all the WSS and assume
that this eliminates SSTop,
i.e., the average is W0.
- Instead of WSS we also
can take the average of
SSTop = (W0 - WSS) / γ
(Poster Sánchez and Drewes)
Conclusions
• SIRGAS defines the unified vertical reference system by
ellipsoidal heights referring to the GRS80 parameters and
normal heights referring to a global cuasigeoid.
• The level of the cuasigeoid has to be realised in America by
the mean sea level - or another approximation.
• The mean sea level depends on the geographic position.
Therefore a kind of average has to be computed.
• The mean sea level also depends on the epoch of definition.
Therefore a reference epoch has to be defined.
• Because the (cuasi)geoid varies less than the sea level, one
could include in the averaging of the sea level also some
continental stations with precise ellipsoidal and normal
heights as well as height anomalies (e.g., SIRGAS2000).
IAG
PAIGH
ANNEX VIII
FUTURE ACTIVITIES
NIMA
Realización del nivel del Cuasi-geoide
Chile
Bolivia
Paraguay
Venezuela
Brasil
∆ WVen= ∆ HVen
∆ WBra= ∆ HBra
Perú
W0 ≈ H0
∆ WUru= ∆ HUru
Argentina
Ecuador
Colombia
Uruguay
∆Wi = ∆Hi
HiClásico = H0 + ∆Hi
Definición de H0
I. Determinación de SSTop por altimetría satelital
Mareógrafo
H
SSTop
0
H
h
HN
∆HSSTop
SSTop
(Cuasi-)geoide
ζ
∆H
∑
=
SSTop
0
i
n
∆H
=∫
l
l : extensión total de la costa
en América del Sur
H0
N
Elipsoide
Definición de H0
II. Posicionamiento GPS en los mareógrafos de referencia
∆H i
∑
Mareog
H0
HN =0
∆H i = hi − ζ i
=
n
Problema: El nmm actual no coincide con el nmm
en la época de definición (HN ≠ 0)
Solución: Reducción a la época de definición
 dH i 

 ∆t
 dt 
⇒ Posicionamiento GPS repetitivo y registros mareográficos
(SIRVEMAS, EVAMARIA)
Definición de H0
III. Relación h, HN, ζ (SIRGAS2000)
∆H i = hi − ζ i − H
N
i
H
Marco
0
∆H
∑
=
i
n
Problema:
• La determinación del Cuasi-geoide es muy imprecisa, (dm...m)
• Las anomalías gravimétricas se refieren a los sistemas clásicos
• Las alturas niveladas parten de mareógrafos, que no coinciden con el
(cuasi-)geoide y que no están conectados entre si
• Las alturas se han modificado por movimiento verticales, es decir que el
posicionamiento GPS y altura nivelada no se refieren a una misma época
HNi (tj) → hi(tk)
Solución:
• Utilización de un modelo de cuasi-geoide derivado de las misiones
satélitales gravimétricas
• Densificación del modelo de cuasi-geoide mediante anomalías
locales (iteración)
• Corrección de HNi mediante H0 y consideración del cambio con el tiempo
(tk-tj) dH/dt
• Conexión de las redes → discrepancia entre los sistemas clásicos
Corrección de cada sistema nacional con respecto a H0
Combinación:
∆H
H
=∫
l
∆H i
∑
Mareog
H0
=
n
∆H i
∑
Marco
H0
=
n
SSTop
0
Mareógrafos (línea de costa)
Continente
Corrección para cada sistema local:
∆H Individual = ∆H iMareog +SSTop − H 0
Actividades URGENTES relacionadas con la realización
del nivel de referencia vertical en América del Sur
→ Conexión de las redes de nivelación entre
países vecinos
→ Nivelación geométrica de las estaciones
SIRGAS2000
→ Gravimetría correspondiente
Actividades INMEDIATAS relacionadas con la realización
del nivel de referencia vertical en América del Sur
→ Determinación UNIFICADA de un modelo de
cuasi-geoide basado en un modelo gravitacional
global y densificado mediante anomalías
locales (iteración)
→ Determinación de la topografía de la superficie
del mar (SSTop) referida al mismo modelo
gravitacional global
Conclusiones
Debemos concentrar nuestros esfuerzos en:
• Nivelación geométrica de las estaciones SIRGAS2000
• Conexión de las redes de nivelación entre países vecinos
• Identificación y digitación de todas las líneas de nivelación que
conectan las estaciones SIRGAS2000
• Digitación de las redes de nvelación nacionales
• Identificación de los nodos en las redes
• Determinación UNIFICADA del cuasi-geoide
• Determinación de la topografía de la superficie del mar (SSTop)
(posicionamiento GPS de los mareógrafos)
IAG
PAIGH
ANNEX IX
STATUTE OF THE SIRGAS PROJECT
(APPROVED BY THE COMMITTEE ON OCTOBER 22, 2002)
NIMA
Statute of the SIRGAS Project
Geocentric Reference System for the Americas
The SIRGAS Project (Geocentric Reference System for the Americas) by its
objectives and scope has a Pan-American profile, its execution aims at all
nations of the Americas and the Caribbean, and its regulation is contained in
the following articles.
General Objectives
Art. 1. The main objective of the SIRGAS Project is to define, materialize and
maintain the tri-dimensional geocentric reference system for the Americas. This
objective includes:
a) Definition of a tri-dimensional geocentric reference system.
b) Establishment and maintenance of a geocentric reference frame (set of
stations with high precision geocentric coordinates [X, Y, Z] and their
variation with time [Vx, Vy, Vz]).
c) Definition and establishment of a geocentric datum.
d) Definition and materialization of a unique vertical reference system with
consistent physical and geometric heights and the determination of the
variations of the reference frame with respect to time.
Art. 2. The specific objectives of the SIRGAS Project are all those related to the
main objective, among them the following can be mentioned:
a) Planning, promotion and coordination of the technical activities required
to accomplish the main objective.
b) Promotion and dissemination of the advances, results and
accomplishments of the Project, in order to maximize the benefits to the
countries of the region.
c) Permanent participation in the International Association of Geodesy
(IAG) and in the Pan-American Institute of Geography and History
(PAIGH), in order to exchange up-to-date information and knowledge on
technical and scientific subjects related to the Project.
d) Encouragement, among the member states, of the homogeneity of the
technical knowledge involved in the scope of the Project, including the
dissemination of the scientific and technological advances which
contribute to its improvement.
e) Promotion and coordination of all activities that contributes to the
accomplishment of the proposed objectives, including among them the
connection of the pre-existing geodetic systems to SIRGAS.
Members
Art. 3. Only American and Caribbean states can be Members of SIRGAS. To
join the Project, it is just necessary to write to the Steering Council (defined in
Art. 12) mentioning the interest and the will to actively work towards the
accomplishment of the objectives and to appoint corresponding representatives
(according to Art. 7).
Art. 4. The sponsoring institutions of the Project –International Association of
Geodesy (IAG), Pan-American Institute of Geography and History (PAIGH) and
U.S. National Imagery and Mapping Agency (NIMA)– are considered Members
with the same rights and attributions as the member states.
Art. 5. Other states, entities and persons can be observing members, providing
that they do not aim at profits, and they manifest their intention to participate as
such or they are invited by the Project. In any case they must be accepted by
the Executive Committee (defined in Art. 9).
Art. 6. In addition, it is established the category of cooperative state or entity
for those that have required or have been invited by the Project to participate as
a contributor in scientific, technical or economic terms. The processing centers
that participate in the Project are considered as such.
Art. 7. The national representatives will be the persons appointed by the
member states, through the entities that congregate the scientists and
technicians in geodesy and related subjects, throughout procedures established
in each country. The sponsoring entities will appoint their own representatives.
Organization
Art. 8. The following structure units with corresponding roles, defined in the
next articles, are established:
a)
b)
c)
d)
e)
Executive Committee
Steering Council
Working Groups
Technical Meetings
Scientific Council
Art. 9. The Executive Committee is the supreme unit of the SIRGAS Project
and establishes its scientific, technical and administrative directions. Its
composition and functioning will be governed by the following rules:
a) It will be composed by one representative of each member state and one
of each sponsoring institution. Each member will have one vote and can
appoint a substitute representative who will replace the representative in
case he or she is not present.
b) It will ordinarily meet each 4 years. The ordinary meetings will be held
during the same year as the General Assembly of IAG and, if possible,
simultaneously to it.
c) It will be chaired by the president of the Project.
d) The authorities –defined in Art. 12– will have voice but not vote, except
when taking part of the official delegation of his or her country.
e) The observers, cooperative states or entities and the members of the
Scientific Council will have voice but not vote.
Art. 10. The place of the next ordinary meeting will be decided at each ordinary
meeting, being the place selected from the various cities offered by members of
the Project. The corresponding agenda will be prepared by the Project
authorities.
Art. 11. It is established for the resolutions of the Executive Committee:
a) Quorum: it is given by the vote –in presence or by correspondence- of
two third parts of the members.
b) Vote: assuming fulfilled the quorum as mentioned in a), the proposal that
has the simple majority of votes in favor is accepted.
Art. 12. The Steering Council is composed by the Project authorities, who
are: the president and the vice-president of the Project and the presidents of the
working groups.
Art. 13. The candidates to the position of authorities must be proposed to the
Executive Committee by the entities that sponsor them and must have
conditions of technical capacity internationally recognized in the subjects of the
Project.
Art. 14. The states or the sponsoring entities will commit themselves to support
their candidates in fulfilling the responsibilities established in this statute.
Art. 15. The president and vice-president of the Project will be elected at the
ordinary meetings of the Executive Committee, and their term will last 4 years,
being eligible to be re-elected for a second term. The presidents of the working
groups will be appointed by the president of the Project in coordination with the
Executive Committee, and there will be no fixed time for their term.
Art. 16. The presidency of the project and of the working groups will specially
take into account the opinion of the scientific council when taking decisions and
writing resolutions, considering the recognized professional hierarchy of its
components.
Art. 17. The working groups will be established or dissolved by the Executive
Committee according to the Project needs. At the moment of their creation,
their general and particular objectives will be established.
Art. 18. The working groups and their objectives will initially be the following:
I – Reference System: to define the geocentric reference system for the
Americas and to coordinate its establishment and maintenance.
II – Geocentric Datum: to coordinate the densification of the geocentric
reference frame for the Americas within each member estate of the
Project.
III – Vertical Datum: to define a unified height system for the Americas and
to coordinate its establishment and maintenance.
Art. 19. The working groups will be composed by their presidents and by
experts who have scientific and technical knowledge and experience in the
subject. The names of such experts can be proposed by members or be invited
by the Project authorities. In any case the final incorporation of an expert to a
Working Group will be performed by the corresponding Working Group
president, and ratified by the president and vice-president of the Project.
Art. 20. The presidents of the working groups will permanently keep the
presidency of the Project posted about the activities carried out in the scope of
the working groups.
Art. 21. The technical meetings will be held whenever scheduled by the
Executive Committee or called by the president of the Project or by the
presidents of the working groups. Their agenda will be prepared by the
corresponding presidents.
Art. 22. The Scientific Council will have the following missions:
a) To advise the presidency of the Project about geodetic techniques,
procedures and executions, and eventually about related subjects that
better satisfy the imposed requirements.
b) To intervene with working groups and national representatives in order to
give directions to their activities, from the scientific point of view, in a way
to better contribute to the accomplishment of the Project objectives.
c) To explain, at the general meetings of the Executive Committee or at the
particular meetings of the working groups, its opinion about the progress
of the activities, recommendations that can improve, according to its
understanding, the efficiency, and its own analysis about possible action
steps that would enable to optimize results and to facilitate future
activities.
Art. 23. The Scientific Council will be governed by the following rules:
a) The appointment of members of the scientific council, among those
proposed by representatives in the Executive Committee, observers,
Project authorities or cooperative entities, will have a permanent nature,
and must be accepted by the Executive Committee.
b) The incorporation proposal must be submitted along with a report of the
professional experience showing the competence and expertise
necessary to occupy the position.
c) Periodically they will inform the presidency of the Project and of the
working groups about the developed activities.
Data policy
Art. 24. The national representatives will deal with the authorities of their
respective countries to get the corresponding authorizations to have all data
needed by the Project freely available to it.
Art. 25. The availability mentioned in Art. 24 will be for scientific and/or
educational use only and the sources that provide them will be explicitly
mentioned every time they are used.
Art. 26. The use and distribution of the national data utilized during the Project
execution will be regulated by the particular rules of each member state, being
requested to the national representatives to arrange their widest availability.
Art. 27. The member states will collaborate with the publication of the respective
metadata in the webpage of the Project, including the required conditions for
their use.
Art. 28. The computation centers will facilitate to the member states and to the
cooperative entities the access to data, to computation procedures, to their
results and to all available information related to the Project.
Language
Art. 29. The official languages of the Project will be Spanish, Portuguese and
English. In any case, the Spanish version of this statute will prevail.
Webpage
Art. 30. The Project will have a webpage, whose edition will be under the
president´s responsibility, with the collaboration of the vice-president. The
presidents of the working groups will have the obligation of supplying the
information to be published. The participant states, the observing members and
the sponsoring and cooperative entities will also contribute with relevant news
and periodic information. All Project reports will be released through the
webpage.
Art. 31. The page contents should be constantly updated, being recommended
a complete review at least two times a year.
Art. 32 (transitory). The present statute will take effect at the moment of its
approval by the Executive Committee.
IAG
PAIGH
ANNEX X
LIST OF ATTENDEES TO THE SANTIAGO MEETING
NIMA
IAG
PAIGH
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
NAME
Alfonso Tierra
CAP. Rafael Delgado
Carlos Alberto Corrêa e Castro Jr
Claudio Brunini
Daniel Del Cogliano
Denizar Blitzkow
Eduardo Lauría
Fabian Barbato
Felipe Eduardo Vásquez Moya
Hayo Hase
Hector Parra
Hermann Drewes
J. Derek Fairhead
Johannes Ihde
Jorge Velásquez
Jose Napoleón Hernández
Juan Carlos Baez Soto
Jürgen Klotz
Klaus Kaniuth
Laura Sánchez
Lautaro Díaz
Lorenzo Centurion Carmona
Luiz Paulo Souto Fortes
María Cristina Pacino
Maria Paula Natali
MAY. Alvaro Hermosilla
Melvin Hoyer
Muneendra Kumar
Roberto Teixeira Luz
Silvio R. Correia de Freitas
Sonia Costa
TCL. Oscar Cifuentes
TCL. Rodrigo Barriga
TCL. Rodrigo Maturana
Washington Vinuez
Wolfgang Schluter
Wolfgang Seemueller
NIMA
COUNTRY
Ecuador
Ecuador
Brazil
Argentina
Argentina
Brazil
Argentina
Uruguay
Bolivia
Chile
Chile
Germany
UK
Germany
Ecuador
Venezuela
Chile
Germany
Germany
Colombia
Chile
Paraguay
Brazil
Argentina
Argentina
Chile
Venezuela
USA
Brazil
Brazil
Brazil
Chile
Chile
Chile
Ecuador
Germany
Germany
E-MAIL
atierra@espe.edu.ec
vrafaeldelgado@hotmail.com
castrojr@ibge.gov.br
claudio@fcaglp.unlp.edu.ar
daniel@fcaglp.unlp.edu.ar
dblitzko@usp.br
jdivgeod@mapas.igm.gov.ar
fbarbato@fing.edu.uy
capeduvas@yahoo.com
hase@wettzell.ipg.de
hparra@igm.cl
drewes@dgfi.badw.de
jdf@getech.leeds.ac.uk
ihde@ifag.de
jorgevqz@hotmail.com
jhernandez@igvsb.gov.ve
jbaez@udec.cl
klotz@gfz-potsdam.de
kaniuth@gdfi.badw.da
lsanchez@igac.gov.co
calculo@igm.cl
lcenturion@highway.com.py
fortes@ibge.gov.br
mapacino@fceia.uns.edu.ar
paula@fcaglp.unlp.edu.ar
ahermosilla@igm.cl
mhoyer@luz.ve
kumarm@nima.mil
roberto@ibge.gov.br
sfreitas@cce.ufpr.br
soniamaria@ibge.gov.br
ocifuentes@tigo.cl
rbarriga@igm.cl
rmaturana@igm.cl
wasvin@hotmail
schlueter@wettzell.ifag.de
seemueller@dgfi.badw.da
IAG
PAIGH
ANNEX XI
PICTURES OF THE MEETING
NIMA

H - IBGE

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