|
- 5 آبان ماه ، حضور پروفسور
Professor Lars Erik Sjöberg
در زنجان
- تصویر
سمینار روز 6 آبان ماه در دانشگاه زنجان
Sjöberg, Lars Erik
Tel: +46 8 790 7330, Fax: +46 8 790
7343
Email: sjoberg@geomatics.kth.se <sjoberg@geomatics.kth.se>
Personal web-page:
Home Page
Position: Professor of Geodesy and
Head of the Division of Geodesy
Qualifications: Master of Science in
Land Surveying and PhD in Geodesy,
KTH, Stockholm
Research Interests: Physical,
Geometrical and Satellite geodesy,
Geodynamics
Name:
Lars Erik Sjöberg
Civil status:
Married, with two children
Academic degrees:
1971
Master of Science in Surveying, KTH,
Stockholm
1975 PhD in Geodesy, KTH
Membership in professional
organisations:
1982-2002 The Nordic
Geodetic Commission Presidium
1984- The Swedish
National Committee for Geodesy and
Geophysics: Swedish IAG
Representetive
1981- The
Geophysical Society of Sweden (GSS)
1984- The GSS
committee, Chairman: 1991-
1989- Corresponding
member of Deutsche Geodätische
Kommission
1989 – 1991 Editorial Board of
Manuscripta Geodaetica
1991 – 1995 Joint Editorial
Board of MG and Bulletine Geodesique
2004- Editorial
Board of Studia Geophys.et Geod.
1975- Member ca. 20
IAG SSGs; chaired SSGs 4.91, 4.96,
5.121
Professional
experiences:
1971-1975
Assistant Professor in Geodesy,
Department of Geodesy, KTH
1976-1977
Research Associate in Geodesy, KTH
1977-1980
Senior Research Associate in
Geodesy, KTH, (1/2 time)
1977-1980
Lecturer in Geodesy, KTH (1/2 time)
Jan 1977 - Apr 1978
Research Associate, Department of
Geodetic Science, The Ohio State
University, Columbus, Ohio, USA
Oct
1978-
Docent in Geodesy, KTH
Sep 1980- May
1984 Docent in
Geodesy, KTH, Associate professor at
the National Land Survey of Sweden
Apr 1981- May
1984 Co-opted
professor in Geodesy, University of
Uppsala
Jun 1984
- Professor
in Geodesy, KTH
Jul 1988 - Dec
1992 Head of the
Department of Geodesy, KTH
Jan 1993 – -August 1998
Head of the Department of Geodesy
and Photogrammetry, KTH
Jul 1990 - June
1993 Deputy Dean of
School of Surveying
1981-
2006
Supervision of 17 successful
Postgraduate and Ph.D. students
Study and research leaves:
Jan - Feb 1997 Oct.-Dec. 2002:
Research visit to Dronning Maud
Land, Antarctica Curtin University,
Perth, and UNSW, Sydney, Australia
Jan 1977-Apr 1978:
Research
Associate, Department of Geodetic
Science, The Ohio State University
March 1997 – June 1997:
The Department of Surveying
Engineering, The University of New
Brunswick, Fredericton, Canada
Jan 1983-June 1983:
Fellow of the Alexander-von-Humboldt
Foundation, Department of Geodetic
Science, The Stuttgart University
Visiting Professor
June 1988-Jul 1988:
The Department of Surveying
Engineering, The University of New
Brunswick, Fredericton, Canada.
Recognition:
- August 1991:
Elected as IAG Fellow
Publications:
About 235 titles
چکیده سمینار پروفسور در دانشگاه
زنجان
Abstract
The remove-compute-restore (RCR)
technique is the most well known method
for regional gravimetric geoid
determination today. Its basic theory is
the first-order approximation of either
Molodensky’s
method for quasi-geoid determination or
the classical geoid
modelling by
Helmert’s second method of
condensing the topography onto the
geoid. Although the basic approximate
formulae do not meet today’s demands for
a 1-cm geoid, it is sometimes assumed
that the removal of the less precise
long-wavelength terrestrial gravity
anomaly field from
Stokes’s integral by utilizing a
higher-order reference field represented
by a more precise Earth gravity model
(EGM) and the restoration of the EGM as
a low-degree geoid contribution will
produce a geoid model of the desired
accuracy. Further improvement is
achieved also by removing and restoring
a residual topographic effect, which
favourably
smoothes the gravity anomaly to be
integrated in
Stokes’s formula. However, it is
shown here that the RCR technique fails
to tune down the long-wavelength gravity
signal from the terrestrial data, and
the EGM actually only reduces, in a non-optimised
way, the truncation error
committed
by limiting the Stokes integration to a
small region around the computation
point. Hence, in order to take full
advantage of a precise EGM, especially
one from new dedicated satellite
gravimetry,
Stokes’s
kernel must be modified in a suitable
way to match the errors of terrestrial
gravity, EGM and truncation. In
addition, topographic, atmospheric and
ellipsoidal effects must be carefully
applied.
خلاصه:
امروزه روش حذف-محاسبه-جبران (RCR)
یکی از روشهای شناخته شده در تعیین ژئوئید
محلی است. مبنای تئوری این روش تقریب
اولیه از روش مولودنسکی برای تعیین شبه
ژئوئید و یا روش کلاسیک مدلسازی ژئوئید از
طریق فشرده سازی توپوگرافی بر روی ژئوئید
از طریق متد دوم هلمرت میباشد. گرچه اساسا
تقریبات اولیه فرمولها در این روش امکان
حصول به دقت 1 سانتیمتر را عملا غیر ممکن
میکند ولی تصور اینکه با حذف و سپس جبران
طول موج های بلند داده های مدل جهانی و
توپوگرافی از داده های جاذبی در فرمول
استوکس، بتوان از فرمولهای تقریبی برای
تصحیحات استفاده کرد هم تصور نابجایی است.
زیرا این روش به اندازه فرمول اصلی استوکس
به تقریبات حساس هست. ضمن اینکه این روش
به صورت کاملا غیر بهینه داده های زمینی
و مدل جهانی را ترکیب مینماید. به منشور
استفاده حداکثر و بهینه از پتانسیل داده
ای جهانی ضروری است تابع استوکس بروش
مناسبی تغییر یابد تا خطای ناشی از برش
این تابع در محدوده خارج از زون مرکزی به
حداقل ممکن برسد. ضمنا تصحیحات توپوگرافی،
اتمسفری و بیضوی بایستی با دقت بالا اعمال
شوند.
مشاهده جزئیات بیشتر
بر گرفته از وب سایت دکتر رامین
کیامهر
www.kiamehr.tk |
