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WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program of SCAR WGGGI Report 2000 - 2002 Prepared by Jan Cisak - project leader
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WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

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Page 1: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

Atmospheric Impact on GPS Observations

Project of GEODESY/GIANT

program of SCAR WGGGI

Report 2000 - 2002Prepared by Jan Cisak - project leader

Page 2: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

Project Background

• Establishment of the project - Tokyo 07- 2000

• Receiving a grant from Polish Committee on Scientific Research

Warsaw 03-2001• Report in Siena coordinators meeting

Siena 07 - 2001• Presentation of first results on AGS’01

St. Petersburg 07 - 2001• Presentation of Iono WG Activities

St. Petersburg 07 - 2001• Presentation of WGGGI/GIANT Activities

Darmstadt 01- 2002• International Workshop

Warsaw 05 - 2002• WGGGI meeting

Shanghai 07 - 2002

Page 3: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

International Cooperation

• Irk Shagimuratov - IZMIRAN, Kaliningrad, Russia• Yevgen Zanimonskiy - „Metrologia” Kharkov, Ukraine• Alla Zanimonskaya - „Metrologia” Kharkov, Ukraine• Reinhard Dietrich - Institut für Planetare Geodäsie

Technische Universität Dresden• Sibylle Vey - Institut für Planetare Geodäsie

Technische Universität Dresden • Henk Brolsma - Australian Antarctic Division • John Manning - National Mapping Division, Australia• Glenn Johnston - National Mapping Division, Australia• Larry Hothem - National Mapping Division

US Geological Survey • Michael Mayer - Geodetic Institute (GIK) of the University • of Karlsruhe (Germany).• Bjorn Johns - UNAVCO     • Joachim Feltens - Iono_WG Chairman ESOC, Darmstadt• Norbert Jakowsky - Deutsches Zentrum für Luft- und • Raumfahrt e.V. (DLR), Institut für Kommunikation und • Navigation, NL, Neustrelitz • Uk Han - Dept. of Environmental Sci. Korea Military • Academy Seoul, Korea

Page 4: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

Contribution of Polish researchers and Organizations to the project

• Jan Krynski - Institute of Geodesy and • Cartography, Warsaw• Jan Cisak - Institute of Geodesy and Cartography, • Warsaw• Marcin Sekowski - Institute of Geodesy and • Cartography, Warsaw• Wlodzimierz Baran – University of Warmia and• Mazury, Olsztyn• Andrzej Krankowski - University of Warmia and• Mazury, Olsztyn• Pawel Wielgosz - University of Warmia and• Mazury, Olsztyn• Mariusz Figurski – Warsaw University of • Technology, Warsaw• Michal Kruczyk - Warsaw University of • Technology, Warsaw

Page 5: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

Studying of the repeatability of the vector components during

the ionospheric storms

STORM OF 15-18 FEB 1999

DAVIS - MAWSON permanent 24-hours obserwations

-60.0-50.0-40.0-30.0-20.0-10.0

0.010.020.030.0

13 14 16 17 18 24

13-24 February 1999

[mm

]

DAVIS - MAWSON12:00 - 24:00 UTC

-80.0-60.0-40.0-20.0

0.020.040.060.080.0

13 14 16 17 18 24

13-24 February 1999

[mm

]

DAVIS - MAWSON12:00 - 18:00 UTC

-120.0-100.0

-80.0-60.0-40.0-20.0

0.020.040.060.0

13 14 16 17 18 24

13-24 February 1999

[mm

]

Day-to-day changes of the Davis-Mawson baseline length (636 km)

Page 6: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

Studying of the repeatability of the vector components during

the ionospheric storms

OHIGGINS - ARCTOWSKI permanent 24-hours obserwations

-6.0-5.0-4.0-3.0-2.0-1.00.01.02.03.0

14 15 16 17 18

14-18 February 1999

[mm

]

OHIGGINS - ARCTOWSKI00:00 - 12:00 UTC

-8.0-6.0-4.0-2.00.02.04.06.08.0

14 15 16 17 18

14-18 February 1999

[mm

]

OHIGGINS - ARCTOWSKI06:00 - 12:00 UTC

-8.0-6.0-4.0-2.00.02.04.06.08.0

14 15 16 17 18

14-18 February 1999

[mm

]

Day-to-day changes of the O’Higgins-Arctowski baseline length (132 km)

STORM OF 15-18 FEB 1999

Page 7: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

The ionosphere in Antarctic region has considerable influence on the accuracy determination of the vectors.

Strong correlation between TEC changes and North, East and Up vector components were obtained.

The changing conditions of ionosphere mostly affect height component. The height differences obtained during the quiet and disturbed ionosphere reach a few dozen of millimeters even for 132 km long vectors (O’Higgins-Arctowski).

Because of the great dynamics of the TEC during the ionospheric storms the special attention should be paid to the differences of vectors co-ordinates obtained from semidiurnal GPS sessions.

Conclusions after the first experiments

Page 8: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7D O Y 2 0 0 1

- 1 0

0

1 0

2 0

dH 2

4h s

essi

ons

[mm

]

-40

-20

0

20

40

dH 3

h se

ssio

ns [m

m]

dH B O G O -LA M A 3h sessions

B O G O -JO ZE 24h sessions

E nve lope w as ca lcu la ted on the base o f IG S TE C da ily m aps.

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7D O Y 2 0 0 1

0.4

0.6

0.8

1

1.2

1.4

chi-s

quar

e

24h sessions 3h sessions

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7

D O Y 2 0 0 1

2 0

2 4

2 8

3 2

3 6

4 0

4 4

enve

lop

e o

f V

TE

C [T

EC

U]

228

230

232

234

236

TZ

D f

or B

OR

1 [m

m]

IPS Geomagnetic W arn ing

TZD from E U R E F data se ts

runn ing average 1day in terva l

BO G O -LA M A 24h sessions

3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 0 0 1 0 5 1 1 0D O Y 2 0 0 1

- 4

0

4

8

1 2

1 6

dH

BO

GO

-LA

MA

[mm

]

- 8

- 6

- 4

- 2

0

dD

BO

GO

-LA

MA

[mm

]

3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 0 0 1 0 5 1 1 0D O Y 2 0 0 1

-10

-5

0

5

10

15

20

25

dH

BO

GO

-LA

MA

[mm

]

- 8

- 6

- 4

- 2

0

2

dD

BO

GO

-LA

MA

[mm

]

5 8 6 0 6 2 6 4 6 6 6 8 7 0 7 2D O Y2001

0

5

10

15

20

25

dH

BO

GO

-LA

MA

[mm

]

- 6

- 4

- 2

0

2

dD

BO

GO

-LA

MA

[mm

]

Efects of ionospheric storm on vectors in Europe

STORM OF 3 March 2001

Page 9: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

DAVIS - MAWSON 636 km

-8

-6

-4

-2

0

2

4

6

58 59 60 61 62 63 64 65 66 67

DOY 2001

RE

SID

UA

LS

mm

N

E

U

DAVIS - CASEY 1398 km

-10

-5

0

5

10

58 59 60 61 62 63 64 65 66

DOY 2001

RE

SID

UA

LS

mm

N

E

U

MAWSON - CASEY 2028 km

-15

-10

-5

0

5

10

15

58 59 60 61 62 63 64 65 66 67

DOY 2001

RE

SID

UA

LS

mm

N

E

U

MACA 2028 km

050

100150200250300350400

58 59 60 61 62 63 64 65 66 67

DOY 2001

N AMB. 400%

N ABM. 800 %

% RES. AMB.

MADA 636 km

050

100150200250300350400

58 59 60 61 62 63 64 65 66 67

DOY 2001

N AMB. 400 %

N AMB. 800 %

% RES. AMB.

DACA 1398 km

0

50

100

150

200

250

58 59 60 61 62 63 64 65 66 67

DOY 2001

N AMB. 400%

N AMB. 800%

% RES. ABM.

MAWSON - O'HIGGINS 4624 km

-60

-40

-20

0

20

40

60

58 59 60 61 62 63 64 65 66 67

DOY 2001

RE

SID

UA

LS

mm

N

E

U

MAOH 4624 km

0

50

100

150

200

250

300

350

58 59 60 61 62 63 64 65 66 67

DOY 2001

N AMB. 400 %

N AMB. 800 %

% RES. AMB.

MAXIONO - parameterAnd number of ambiguityVECTORS

Studying of the repeatability of the vector components during

the ionospheric stormsSTORM OF 3 March 2001

Page 10: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

STORM OF 3 March 2001

2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0 6 5 7 0 7 5D O Y 2 0 0 1

0

2 0

4 0

6 0

VT

EC

for

BO

GO

[TE

CU

]

4Ant-a .grf

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7D O Y 2 0 0 1

0

10

20

30

40

50

VT

EC

for

BO

GO

[TE

CU

]

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7D O Y 2 0 0 1

0

10

20

30

40

50

VT

EC

for

MA

W1

[TE

CU

]

IPS Geom agnetic W arn ing

Envelope o f V TE C varia tions w as ca lcu la ted on the baseof IG S TEC da ily m aps.

Page 11: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

STORM OF 3 March 2001

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7D O Y 2 0 0 1

-20

-10

0

10

20

dH 2

4 h

sess

ion

s [m

m]

dH M A W 1-D A V 1 24h (636km )

E nve lope w as ca lcu la ted on the base o f IG S TE C da ily m aps.

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7

D O Y 2 0 0 1

2 0

2 4

2 8

3 2

3 6

4 0

4 4

enve

lop

e o

f V

TE

C [T

EC

U]

2 .25

2.26

2.27

2.28

2.29

2.3

2.31

TZ

D [m

m]

IPS Geomagnetic W arn ing

TZD from IG S data se ts (G P S output so lu tions)

TZD for D A V 1

TZD for M A W 1TZD for C A S 1

dH D A V 1-C A S 1 (1398km )

dH M A W 1-C A S 1 (2028km )

Daily solutions for heights between Antarctic stations

and tropospheric parameters from IGS solutions

Page 12: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

STORM OF 3 March 2001

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7D O Y 2 0 0 1

-20

-10

0

10

20

dD

24

h se

ssio

ns

[mm

]

dD M A W 1-D A V 1 24h (636km )

E nve lope w as ca lcu la ted on the base o f IG S TE C da ily m aps.

6 1 6 1 . 5 6 2 6 2 . 5 6 3 6 3 . 5 6 4 6 4 . 5 6 5 6 5 . 5 6 6 6 6 . 5 6 7

D O Y 2 0 0 1

2 0

2 4

2 8

3 2

3 6

4 0

4 4

enve

lop

e o

f V

TE

C [T

EC

U]

2 .25

2.26

2.27

2.28

2.29

2.3

2.31

TZ

D [m

m]

IPS Geomagnetic W arn ing

TZD from IG S data se ts (G P S output so lu tions)

TZD for D A V 1

TZD for M A W 1TZD for C A S 1

dD D AV 1-C A S 1 (1398km )

dD M A W 1-C A S 1 (2028km )

Daily solutions for heights between Antarctic stations

and tropospheric parameters from IGS solutions

Page 13: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

STORM OF 3 March 2001

Page 14: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

6 0 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9DO Y2001

-400

-200

0

200

400

dD [m

m]

-400

0

400

800

dH [m

m]dD M A W 1-D AV 1 dH M A W 1-D A V 1

P IN N A C LE (L1& L2c)

6 0 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9DO Y2001

-200

-100

0

100

200

dD [m

m]

-800

-400

0

400

800

dH [m

m]

dD D AV 1-C A S1 dH D AV 1-C A S1

P IN N A C LE (VLBL)

3Ant-a .grf

STORM OF 3 March 2001

Page 15: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

Final Remarks

• Analysis of recent data does not prove considerable influence of ionosphere storm on resolved vector components

• The magnitudes of variations in vector components due to atmospheric impact seem to be dependent on data processing procedure used

• No correlation between the strength of ionospheric storms and variability of vector components derived from GPS data was observed

• Further investigations on– software applied for data processing– parametrization– data modelingare needed to study atmospheric impact

on GPS solutions

Page 16: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

PAPERS PUBLISHED / PRESENTED (1)

• Krankowski, A., Baran, L.W., Shagimuratow, I.I., Cisak, J., (2001): Influence of Ionosphere in Arctic and Antarctic Regions on GPS Positioning Precision, SCAR Report, Publication of the Scientific Committee on Antarctic Research, Scott Polar Research Institute, Cambridge,UK

• Baran, L.W., Wielgosz, P., Cisak, J., Shagimuratow, I.I., (2001): The Response of Polar Ionosphere to a Magnetic Storm Obtained from GPS Observations, SCAR Report, Publication of the Scientific Committee on Antarctic Research, Scott Polar Research Institute, Cambridge,UK

• Kryński, J., Zanimonskiy, Y., (2001): Contribution of Data from Polar Regions to the Investigation of Short Term Geodynamics. First Results and Perspectives, SCAR Report, Publication of the Scientific Committee on Antarctic Research, Scott Polar Research Institute, Cambridge,UK

• Manning, J., Cisak, J., (2002): Overview of the SCAR/WG-GGI/GIANT activities within the project on the Atmospheric Impact on GPS Observations in Antarctica and possible fields of cooperation with IGS/Iono WG. Proceedings of IGS/IAACs Ionosphere Workshop, Darmstadt, 17-18 January 2002

• Krankowski, A., Baran, L.W., Shagimuratow, I.I., Cisak, J., (2001): Influence of Ionosphere in Antarctic Regions on GPS Positioning Precision, Proceedings of IGS/IAACs Ionosphere Workshop, Darmstadt, 17-18 January 2002

• Ephishov I.I., Cisak J., Shagimuratov I.I, Wielgosz P. (2002): Phase fluctuations of GPS Signals at High attitude Ionosphere during the Storm, presented on 16th International Wroclaw Symposium “Electromagnetic Compatibility”, June 25 – 28, 2002

Page 17: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

PAPERS PUBLISHED / PRESENTED (2)

• Cisak, J., (2002): Overview of the SCAR/WG-GGI/GIANT Activities as an Introduction to the Workshop, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Figurski, M, (2002): Atmospheric Impact on Precision of the Positioning in Regional GPS Network, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Krynski, J., (2002): Variations in GPS Solutions versus Atmospheric Delay, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Zanimonskiy, Y., Krynski, J., Cisak, J., (2002): Correlation of the Atmospheric and Geodetic time Series of GPS Results. Impact, coincidence or artifact? Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Krankowski, A., (2002): Modeling of the Ionosphere in Polar Regions, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Shagimuratov, I., (2002): Storm-time Ionospheric Effects Obtained from GPS TEC Measurements, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Wielgosz, P., (2002): Use of Deterministic Ionospheric Component in GPS Observations Processing, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

Page 18: WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATION Shanghai, China, 14 – 17 July 2002 Atmospheric Impact on GPS Observations Project of GEODESY/GIANT program.

WORKING GROUP ON GEODESY & GEOGRAPHIC INFORMATIONShanghai, China, 14 – 17 July 2002

PAPERS PUBLISHED / PRESENTED (3)

• Zanimonskaya, A.Y., Prokopov, A.V., (2002): Some Effects of Ionosphere Model Thickness on GPS Results, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Vey, S., (2002): Tropospheric Research using GPS, Activities in Dresden, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Kruczyk, M., (2002): Tropospheric Delay in GPS Permanent Networks – a Tool for Atmosphere Research, Paper presented at the International workshop on "Atmospheric impact on GPS observations focused on polar regions", 15 May 2002, Warsaw, Poland

• Kryński, J., Zanimonskiy, Y., Wielgosz, P., (2002): Modelling biases in GPS Positioning Based on Short Observing Sessions, Presented at the XXVII General Assembly of European Geophysical Society 2002, Nice, France, 21-26 April 2002.

• Cisak, J., Kryński, J., Zanimonskiy, Y., (2002): GPS and internet in recent remote geophysical research in polar regions (in russian), Paper presented at the International Conference on Modern Progresses of Geodetic Sciences and Industry, 28-30 March, Lvov, Ukraine.

• Kryński, J., Cisak, J., Zanimonskaya, A., Prokopov, A., Zanimonskiy, Y., (2002): On some errors in zenith tropospheric delay determination from GPS data, Paper presented at the International Conference on Modern Progresses of Geodetic Sciences and Industry, 28-30 March, Lvov, Ukraine