National Report of Poland to EUREF 2015 Report of Poland to EUREF 2015 ... 81–87 Morska St., 81-225 Gdynia, ... Trimble 4000 SSI : Jozefoslaw (JOZ2)

National Report of Poland to EUREF 2015

J. Krynski Institute of Geodesy and Cartography, 27 Modzelewskiego St., 02-679 Warsaw, E-mail: [email protected] J.B. Rogowski Gdynia Maritime University, 81–87 Morska St., 81-225 Gdynia, E-mail: [email protected] 1. Introduction

Since 2013 the main geodetic activities at the national level in Poland concentrated on maintenance of gravity control, continuing operational work of permanent IGS/EPN GNSS stations, GNSS data processing on the regular basis at the WUT and MUT Local Analysis Centres, activities of MUT and WUT EPN Combination Centre, activity within the EUREF-IP Project, works towards monitoring troposphere, monitoring ionosphere and ionospheric storms, status of the ASG-EUPOS network in Poland, modelling precise geoid, the use of data from satellite gravity missions, monitoring of Earth tides, activity in satellite laser ranging and in geodynamics.

2. Maintenance of gravity control and gravity survey for geodynamic research

Absolute gravity measurements were carried out on regular basis with the use of FG5-230 gravimeter in the Jozefoslaw Astrogeodetic Observatory of the Warsaw University of Technology (WUT) since 2005 (Fig. 1). For most of the year 2014 the FG5-230 was serviced by the manufacturer.

Fig. 1. Absolute gravity surveyed with the FG5-230 at Jozefoslaw (100 cm height)

Gravimetric investigations at Borowa Gora

Geodetic – Geophysical Observatory of the Institute of Geodesy and Cartography (IGiK) were continued (Dykowski and Krynski, 2014). A series of absolute gravity measurements on the test stations of the Borowa Gora Geodetic-Geophysical Observatory conducted on monthly basis with the A10-020 gravimeter since September 2008 (Fig. 2) shows

high quality of A10 data. For most of the year 2014 the A10-020 was serviced at Micro-g.

Fig. 2. Absolute gravity surveyed with the A10-020 at Borowa Gora (pillar level)

The comprehensive study on the use of the A10-020 gravimeter for the establishment of gravity control was conducted (Krynski and Dykowski, 2014a). Careful analysis of the data gathered resulted in the estimation of the Total Uncertainty budget for the A10-020 gravimeter.

Activities towards the realization of the project on modernization of the Polish gravity control were continued. The team of IGiK conducted final processing of gravity observations at 169 base stations of the gravity control PBOG14 taking into consideration verified tidal corrections, calibration parameters of relative gravimeters and the A10-020 gravimeter, results of comparison campaigns of absolute gravimeters. Corrections to zero-tide system were also calculated. Quality of the new gravity control in Poland was preliminarily assessed. The relation between the existing POGK98 gravity system in Poland and the PBOG14 preliminarily determined using data on 77 common stations (Fig. 3). The mean difference and the standard deviation are 12.3 μGal and 18.6 μGal, respectively (Krynski and Dykowski, 2014b).

The team of WUT performed in 2014 absolute gravity determination with the FG5-230 gravimeter on 21 fundamental stations of gravity control following the project on modernization of the Polish gravity control (Krynski et al., 2014). Gravity values determined after applying all standard corrections including self-attraction and diffraction corrections were reduced to zero tide system, common to new vertical system in Poland. Each fundamental station was linked with an eccentric station and a base station with relative gravity survey. At each gravity station a vertical gravity

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gradient was determined with at least 2 relative gravimeters.

Fig. 3. Gravity differences between PBOG14 and POGK98

New results on gravity change in Finland 1962-

2010 from the comparison of legacy relative measurements with new measurements made with the A10-020 in 2009-2010 were obtained (Mäkinen et al., 2014).

3. Participation in IGS/EPN permanent GNSS networks

3.1. Operational work of permanent IGS/EPN stations

Permanent IGS and EPN GNSS stations operate in Poland since 1993. Recently 18 permanent GNSS stations (Table 1), i.e. Biala Podlaska (BPDL), Borowa Gora (BOGO, BOGI), Borowiec (BOR1), Bydgoszcz (BYDG), Gorzow Wielkopolski (GWWL), Jozefoslaw (JOZE, JOZ2), Krakow (KRAW, KRA1), Lamkowko (LAMA), Lodz (LODZ), Katowice (KATO), Redzikowo REDZ (Suwalki (SWKI), Ustrzyki Dolne (USDL), Wroclaw (WROC) and Zywiec (ZYWI) (Fig. 4) operate in Poland within the EUREF program. The stations BOGI, BOR1, JOZE, JOZ2, LAMA and

WROC operate also within the IGS network (http://www.epncb.oma.be/_trackingnetwork/stations.php). A brief characteristics of those stations is given in Table 1 and Table 2. Data from those stations are transferred via internet to the Local Data Bank for Central Europe at Graz, Austria and to the Regional Data Bank at Frankfurt/Main, Germany and together with data from other corresponding stations in Europe, were the basis of the products that are applied for both research and practical use in geodesy, surveying, precise navigation, environmental projects, etc.

Four of those stations, i.e. BOGI, BOR1, JOZ2 and WROC participated also in IGS Real-time GNSS Data project. The station WROC since 2014 is also included into the IGS Multi-GNSS Experiment (MGEX) pilot project (http://igs.org/mgex).

The EPN stations at Borowa Gora (BOGI), Borowiec (BOR1), Jozefoslaw (JOZ2, JOZ3), Cracow (KRAW, KRA1), Lamkowko (LAM5), and Wroclaw (WROC) take part in the EUREF-IP project (http://igs.bkg.bund.de/root_ftp/NTRIP/stre ams/streamlist_euref-ip.htm) (Fig. 5, Table 3).

Fig. 4. EPN/IGS permanent GNSS stations in Poland (2014)

Table 1. Permanent GNSS stations in Poland

Name (abbreviation) Latitude Longitude Status Receiver

Biala Podlaska (BPDL) 52º02'07" 23º07'38" EUREF TRIMBLE NetR5

Borowa Gora (BOGI) 52º28'30" 21º02'07" IGS, EUREF Javad TRE_G3T DELTA

Borowa Gora (BOGO) 52º28'33" 21º02'07" EUREF TPS Eurocard

Borowiec (BOR1) 52º16'37" 17º04'24" IGS, EUREF TRIMBLE NetRS

Bydgoszcz (BYDG) 53º08'04" 17º59'37" EUREF TRIMBLE NetR9

Gorzow Wielkopolski (GWWL) 52º44'17" 15º12'19" EUREF TRIMBLE NetR9

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http://www.epncb.oma.be/_trackingnetwork/stations.php

http://www.epncb.oma.be/_trackingnetwork/stations.php

http://igs.bkg.bund.de/root_ftp/NTRIP/stre

Jozefoslaw (JOZE) 52º05'50" 21º01'54" IGS, EUREF Trimble 4000 SSI

Jozefoslaw (JOZ2) 52º05'52" 21º01'56" IGS, EUREF LEICA GRX1200GGPRO

Katowice (KATO) 50º15'11" 19º02'08" EUREF TRIMBLE NetR5

Krakow (KRAW) 50º03'58" 19º55'14" EUREF Ashtech μZ-12

Krakow (KRA1) 50º03'58" 19º55'14" EUREF TRIMBLE NetR5

Lamkowko (LAMA) 53º53'33" 20º40'12" IGS, EUREF LEICA GRX1200+GNSS

Lodz (LODZ) 51º46'43" 19º27'34" EUREF TRIMBLE NetR9

Redzikowo (REDZ) 54º28'21" 17º07'03" EUREF TRIMBLE NetR9

Suwalki (SWKI) 54º05'55" 22º55'42" EUREF TRIMBLE NetR9

Ustrzyki Dolne (USDL) 49º25'58" 22º35'09" EUREF TRIMBLE NetR9

Wroclaw (WROC) 51º06'47" 17º03'43" IGS, EUREF LEICA GR 25

Zywiec (ZYWI) 49º41'12" 19º12'21" EUREF TRIMBLE NetR9

Table 2. Characteristics of Polish EPN stations

4 char Station

ID

Domes Number

Location/ Institution

Receiver/ Antenna

Started operating/

as EPN station

Meteo Sens./ Manufacturer

Data transfer blocks

Observations performed

BOGI 12207M003

Borowa Gora Inst. of

Geodesy and Cartography

Javad TRE_G3T DELTA

ASH701945C_M SNOW

3JAN2001/ since

265/2002 (GPS week No 1185)

LB-710HB LAB-EL Poland

MET4A Paroscientific

Inc.

24 h 1h

Ground water level Astrometry

Gravity GPS/GLONASS

Geomagnetic field

BOGO 12207M002

Borowa Gora

Inst. of Geodesy and Cartography

TPS Eurocard ASH700936C_M

SNOW

08JUN1996/ since

182/1996 (GPS week No 0860)

LB-710HB LAB-EL Poland

24 h 1h


Gravity GPS/GLONASS

Geomagnetic field

BOR1 12205M002

Borowiec Space

Research Centre, PAS

Trimble NetRS AOAD/M_T

NONE

10JAN1994/ since

365/1995 (GPS week No 0834)

HPTL.3A NAVI Ltd. SKPS 800/I Skye Instr.

Ltd. ARG

10/STD Skye Instr

Ltd.

24 h 1h

SLR GPS/GLONASS

Time service

BPDL 12223M001

Biala Podlaska

Head Office of Geodesy

and Cartography

Trimble NetR5 TRM55971.00

TZGD

4DEC2007/ since

160/2008 (GPS week No 1483)


Inc.

24 h 1h GPS/GLONASS

BYDG 12224M001

Bydgoszcz Head Office of Geodesy

and Cartography


SCIS

4DEC2007/ since

160/2008 (GPS week No 1483)


Inc.

24 h 1h

GPS/GLONASS/Galileo/ SBAS

GWWL 12225M001

Gorzow Wielkopolski Head Office of Geodesy

and


SCIS

10DEC2007/ since

160/2008 (GPS week No 1483)


Inc.

24 h 1h


3

Cartography

JOZE 12204M001

Jozefoslaw Inst. of

Geodesy and Geod. Astr.,

WUT

Trimble 4000SSI TRM14532.00

NONE

03AUG1993/ since

365/1995 (GPS week No 0834)

LB-710RHMS LAB-EL Poland

24 h 1h


Gravity tidal GPS

JOZ2 12204M002

Jozefoslaw Inst. of

Geodesy and Geod. Astr.,

WUT

Leica GRX1200GGPRO

LEIAT504GG NONE

3JAN2002/ since

257/2003 (GPS week No 1236)

LB-710RHMS LAB-EL Poland


Inc.

24 h 1h

Ground water level Gravity absolute

Gravity tidal GPS/GLONASS

KATO 12219S001

Katowice Marsh. Off. of the Siles.

Prov.


TZGD

30JAN2003/ since

222/2003 (GPS week No 1231)


Inc.

24 h 1h GPS/GLONASS

KRAW 12218M001 Krakow AGH UST

Ashtech μZ-12 ASH701945C_M

SNOW

01JAN2003/ since

026/2003 (GPS week No 1203)

LB-710 LAB-EL Poland

24 h 1h GPS

KRA1 12218M002 Krakow AGH UST


NONE

01JAN2010/ since

080/2010 (GPS week No 1576)


Inc.

24 h 1h GPS/GLONASS

LAMA 12209M001 Lamkowko UWM

Leica GRX1200+GNSS

LEIAT504GG LEIS

01DEC1994/ since

365/1995 (GPS week No 0834)


Inc.

24 h 1h

Ground water level Gravity

GPS/GLONASS

LODZ 12226M001

Lodz Head Office of Geodesy

and Cartography


SCIS

3DEC2007/ since

160/2008 (GPS week No 1483)


Inc.

24 h 1h


REDZ 12227M001

Redzikowo Head Office of Geodesy

and Cartography


SCIS

7DEC2007/ since

160/2008 (GPS week No 1483)


Inc.

24 h 1h


SWKI 12228M001

Suwalki Head Office of Geodesy

and Cartography


SCIS

5DEC2007/ since

160/2008 (GPS week No 1483)


Inc.

24 h 1h


USDL 12229M001

Ustrzyki Dolne

Head Office of Geodesy

and Cartography


SCIS

3DEC2007/ since

160/2008 (GPS week No 1483)


Inc.

24 h 1h


WROC 12217M001

Wroclaw Univ. of

Env. & Life Sciences

Leica GR 25 LEIAR25.R4

LEIT

28NOV1996/ since

329/1996 (GPS week No 0881)


Inc.

24 h 1h

Ground water level GPS/GLONASS/Galileo/

BeiDouQZSS/SBAS

ZYWI 12220S001

Zywiec Marsh. Off. of the Siles.

Prov.


SCIS

30JAN2003/ since

222/2003 (GPS week No 1231)


Inc.

24 h 1h


4

Table 3. Characteristics of Polish EPN stations producing real time data streams

Fig. 5. Polish EPN stations participating in the EUREF-IP project (2015)

Since March 2005 Ntrip Broadcaster is installed at the AGH University of Science and Technology (http://home.agh.edu.pl/~kraw/ntrip.php). The Ntrip Caster broadcasts RTCM and raw GNSS data from 17 sources, mainly from permanent station taking part in the framework of EUREF-IP project.

3.2. Data processing at WUT LAC

The Warsaw University of Technology operates the WUT EPN Local Analysis Centre (LAC) since 1996. WUT LAC contributes to EUREF with final

weekly and daily solutions based on IGS final products, and rapid daily solutions of the EPN subnetwork (Liwosz and Rogowski, 2013). At the end of 2014, the WUT LAC subnetwork (Fig. 6) consisted of 100 GNSS stations (5 stations added and 1 removed in 2014) from which 83 stations observed both GPS and GLONASS satellites.

Fig. 6. EPN stations providing data processed at WUT EUREF LAC (April 2015)

GNSS data are processed in WUT LAC useing the Bernese GNSS Software v.5.2. WUT LAC products, i.e. coordinates in SINEX format and zenith tropospheric delays, can be accessed from

Location St. ID Observations Latitude [deg]

Longitude [deg] Receiver

RTCM type - message types (update rate [s])

Borowa Gora BOGI GPS+GLO 52.48 21.04 Javad TRE_G3T DELTA

RTCM 3.0 - 1004(1),1006(10),1008(10), 1012(1)

Borowiec BOR1 GPS+GLO 52.28 17.07 TRIMBLE NetRS RTCM 2.3 - 1(1),3(10),18(1),19(1), 22(10)

Jozefoslaw JOZ2 GPS+GLO 52.02 21.03 Leica GRX1200GGPro

RTCM 3.0 - 1004(1),1006(60),1008(60), 1012(1)

Jozefoslaw JOZ3 GPS+GLO 52.02 21.03 Leica GRX1200GGPro

RTCM 3.0 - 1004(1),1006(15), 1008(15),1012(1),1033(15)

Krakow KRAW GPS 50.01 19.92 Ashtech μZ-12 RTCM 2.2 - 1(1),3(60),16(60),18(1), 19(1),22(60)

Krakow KRA1 GPS+GLO 50.01 19.92 TRIMBLE NetR5 RTCM 3.0 - 1004(1),1006(10),1008(10), 1012(1),1013(10),1033(10)

Lamkowko LAMA GPS+GLO 53.89 20.67 Leica GRX1200GGPro

RTCM 3.0 - 1004(1),1006(15),1008(15), 1012(1),1019,1020,1033(15)

Warsaw WARS GPS+GLO 52.00 21.00 Leica GRX1200+GNSS

RTCM 3.0 - 1004(1),1006(15), 1008(15),1012(1)

Wroclaw WROC GPS+GLO 51.11 17.06 Leica GR 25 RTCM 3.0 - 1004(1),1006(15),1008(15), 1012(1)

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the following EPN data centres: BKG (ftp://igs.bkg.bund.de/EUREF/products) and EPN (ftp.epncb.oma.be/epncb/product/clusters).

3.3. Data processing at MUT LAC

The Military University of Technology in Warsaw (MUT) LAC Analysis Centre operates since December 2009 (Krynski and Rogowski, 2014). Currently MUT LAC processes data from 138 EPN stations (Fig. 7) using the Bernese GNSS Software v.5.2. 8 stations (ARJ6, JON6, NOR7, OVE6, SVE6, UME6, VIL6,VIS6) were added to the MUT LAC subnetwork since GPS week 1798 and another 3 stations (LEK8, OST6, SKE8) since GPS week 1812.

Fig. 7. EPN stations providing data processed at MUT EUREF LAC (March 2015) (http://www.epncb.oma.be/)

MUT LAC provides weekly and daily coordinates solutions and troposphere solutions. As a reference several stations with coordinates expressed in igb08 are being used

MUT LAC also participates in the new campaign of reprocessing project (repro2) and will provide full solutions for the entire network. The processing has been performed for GPS weeks 835-1771 (18 years) using GAMIT software (only GPS observations). The benchmark test preceding main campaign has been completed. In analysis the revised strategy (in relation to repro1) was used: 2nd and 3rd ionospheric corrections were applied as well as atmospheric loadings (tidal and non-tidal). Additionally some models were updated to the current version of IERS Conventions. MUT will provide three different solutions (MU0 - already delivered, MU1, MU2) with different approaches for antenna modelling and atmosphere loadings.

3.4. Activities of MUT and WUT EPN Combination Centre

The main task of the Analysis Combination Centre (ACC) run by a consortium of the Military University of Technology (MUT), and the Warsaw

University of Technology (WUT) is to combine final weekly and daily, rapid daily and ultra rapid solutions delivered by particular Local Analysis Centres.

The EPN ACC webpage (http://www.epnacc.wat.edu.pl) contains the results of comparison of repeatability of stations coordinates after Helmert transformation as well as parameters of Helmert transformation between each weekly LAC position estimated and the combined EPN solution estimated for the weekly final combinations. Results of comparison of repeatability of horizontal components and vertical component after Helmert transformation for the GPS week 1832 are presented in Figure 8 and Figure 9, respectively.

Fig. 8. Results of comparison of repeatability of horizontal components after Helmert transformation for the GPS week 1832

Fig. 9. Results of comparison of repeatability of vertical component after Helmert transformation for the GPS week 1832

The weekly reports containing the most important information about combinations are sent by the LAC email distribution list. The full combined solutions are still available from the BKG server (ftp://igs.bkg.bund.de/EUREF/products/).

Reports related to the rapid daily and ultra-rapid hourly combinations are also presented on the

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ftp://ftp.epncb.oma.be/epncb/product/clusters

above webpage. Exemplary figure for ultra-rapid hourly solution corresponding to the 22 March 2015, 11 a.m. is presented in Figure 10. Residual

positions time series for all monitored stations can also be found on the webpage.

Fig. 10. Ultra-rapid hourly solution corresponding to the 22 March 2015

3.5. Other EPN and IGS activities

GNSS for meteorology

Research on integrated precipitable water (IPW) time series derived from numerical weather prediction models was continued in 2014 in the Warsaw University of Technology. IPW was investigated as a valuable meteorological and climatologic parameter (Kruczyk, 2014). Tropospheric delay estimates (tropospheric product) on selected EPN and IGS permanent stations (recalculated to IPW) exhibit large information potential for meteorology and climate research. Long time series of integrated precipitable water (IPW) averaged hourly, daily and monthly can serve as climate indicators. As IPW is mostly influenced by global circulation, not surface processes, correlations of IPW with basic meteorological surface parameters on annual and monthly basis (e.g. Fig. 11) for different regions.

Simple charts of IPW/temperature (Fig. 12) which can be treated as climatologic diagrams were suggested and investigated. Some of these charts have been analysed with some climatologic insight - IPW clearly represents diversity of world climates Fig. 13).

The GNSS and Meteo Working Group from Institute of Geodesy and Geoinformatics, Wroclaw University of Environmental and Life Sciences (WUELS) has been investigating a number of aspects of ground- and space- based GNSS

meteorology (Hadas et al., 2014). The research was focused on methodological improvements and validations of Zenith Total Delay/Integrated Water Vapour (ZTD/IWV) estimation algorithms, tomography modelling enhancements, real-time retrievals of ZTD/IWV and application of tomography models to resolve severe weather structure.

Fig. 11. Monthly correlation coefficients (IPW-temperature and IPW-atmospheric pressure) for REYK (Reykjavik, Iceland) and QAQ1 (Qaqortoq, Greenland); multi-year series

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Fig. 12. Climatologic chart temperature [ºC] vs. IPW [mm] for southern hemisphere: CHPI (Cachoeira Paulista, Sao Paulo, Brazil) and THTI (Tahiti, French Polynesia); IGS tropospheric product, multi-year series

Fig. 13. IPW monthly averages for three IGS stations in temperate climate zone of the Northern Hemisphere: NRC1 (Ottawa, Canada) is definitely continental, HERS (Hailsham, Sussex, UK) definitely oceanic, JOZE (Jozefoslaw, Poland) falls in between

ZTD and IWV was estimated in a challenging weather conditions (Rohm et al., 2014a) based on baseline, network or Precise Point Positioning approach using post-processed and predicted orbits and clocks. GNSS proved to be an optimal integrated water vapour data source (e.g. IWV standard deviation with respect the radiosonde data below 3 mm) in all weather conditions. In the presence of severe weather the variability of troposphere estimates was observed doubled and it should be reflected in constraints, otherwise the formal errors increase also by a factor of two.

Studying the ZTD to IWV conversion procedures and quality of integrated ASG-EUPOS – meteorological ground sensors network for IWV (Hordyniec, 2014) retrieval, alternative data sources were used in case direct measurements at the GNSS stations are unavailable. It has been proved that the pressure from standard empirical models (GPT, GPT2, UNB3m) will induce a noise in IWV at the

level of 2.5 mm (Fig. 14). In contrary, hourly data of Numerical Weather Prediction model reduce this discrepancy roughly by 0.6 mm. Still, the numerical forecast needs to be treated with care when applied for high altitude stations as additional bias can occur. A priori wet delay modelling (Saastamoinen model) provides rather crude IWV estimate as 3 mm and higher uncertainties were achieved.

Fig. 14. Mean bias and standard deviation [kg/m2] for IWV from ZWD a priori (left) and IWV from ZWD using ZTD estimates (right) w.r.t. IWVs in-situ

Real-time (zero latency) ZTD/IWV retrievals is a

current challenge of GNSS meteorology. Joint WUELS – RMIT research teams developed and globally tested methodology that address this issue (Yuan et al., 2014). The solution was based on the BNC PPP solution, however number of modifications need to be implemented, i.e. antenna phase centre variation models, ocean and Earth tides, advanced mapping functions and a priori information (GPT2), Kalman filter stochastic and functional model modification. These advancements tested against globally distributed IGS stations and radiosonde profiles show that the real-time retrieval of integrated water vapour is feasible with the accuracy of 3 mm.

Continuing development of GNSS tomography methodology, constraints were removed and robust Kalman filtering was applied to retrieve wet refractivities (Rohm et al., 2014b). It has been found that the bottleneck of further development of tomography models and their applications in atmosphere sciences are linked with the constraint equations that limit variability of the troposphere to the limit of standard conditions. The implicit constraints were thus removed from the tomography equation system and Kalman filter was applied to tie the troposphere conditions between observations epochs and the equation system was resolved iteratively with procedure removing outliers in place (Fig. 15).

Applying tomography models to resolve vertical and horizontal structure of Mesoscale Convection System was one of the first attempts world-wide to observe internal processes of severe weather using GNSS signal (Manning et al., 2014). Collaboration between RMIT University and WUELS resulted in resolving one storm event (6 March, Victoria, Australia) using tomography approach. Solution

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was validated against the weather radar data, showing strong correlation of intensive rain with rapid drop of wet refractivity and increase of the wet flux at the front of the storm. These results were found to be in agreement with the conceptual model of Mesoscal Convection System.

Fig. 15. The quality of limited GNSS tomography retrieval with respect the height. RG2SAD - real data a priori for inner and outer model, M2NSAD - synthetic data (normal noise level) a priori for inner and outer model, M1NSAD - synthetic (low observation noise) a priori for inner and outer model, UNB3MGPT – comparison of reference data with UNB3M/GPT field

The new direction of GNSS meteorology

research for the WUELS group is space-based GNSS meteorology. Together with the experts in Radio Occultation from RMIT University and Australian Bureau of Meteorology the quality of RO profiles were investigated in Australia region comparing it with the gold-standard for atmosphere profiling – radiosonde measurements (Norman et al., 2014). The mid and top troposphere retrievals were resolved exceptionally well in the RO profiles, but the unexpected bias in temperature near the stratosphere have been detected.

Monitoring ionosphere and ionospheric storms

The Space Radio-Diagnostic Research Centre (SRRC/UWM) of the University of Warmia and Mazury (UWM) in Olsztyn in collaboration with West Department of the Institute of Geomagnetism, Ionosphere and Radio-Wave Propagation of the Russian Academy of Sciences in Kaliningrad continues the analysis of long time series of GNSS data from EPN stations to study the Earth’s ionosphere. In the last year simultaneous GPS/GLONASS observations from about 700 stations of IGS, EPN, UNAVCO and POLENET networks have been used for studying the dynamics of latitudinal profiles and structure of mid- and high-latitude ionosphere.

A methodology and service that provide estimation of the ionospheric fluctuation activity based on ROT/ROTI calculations has been (Cherniak et al., 2014b). In order to collect data on TEC fluctuation activity over the North Pole, the Northern Hemisphere polar, sub-auroral, and mid-latitude regions geographically located from 45° N geomagnetic latitude to the North Pole were considered. Observations from more than 700 permanent stations that are available from IGS, UNAVCO consortium, and European Terrestrial

Reference System (EUREF) services (Fig. 16a) were involved as an initial database for ROTI map calculations. Monitoring the time derivative of TEC (ROT) is useful for tracing the occurrence of ionospheric irregularities. The ROT values as a measure of phase fluctuation activity are calculated for every considered GNSS station and then detrended for all individual satellite tracks for elevation angles greater than 20°. ROTI, defined as the standard deviation of the detrended ROT values, can then effectively characterize the ionospheric fluctuation activity. Based on the retrieved values of ROT, the ROTI values are calculated over 5-min periods with a sliding window. Because of close interconnection between the Earth’s magnetic field and the ionosphere, the behaviour of the fluctuation occurrence is represented as a function of the magnetic local time (MLT) and the corrected magnetic latitude. Each map, as a daily map, demonstrates the dynamics of ROTI variation within geomagnetic local time (00-24 MLT). ROTI maps are constructed with a grid of 2°×2° resolution. The value in each cell is calculated by averaging over all ROTI values covered by this cell area, and it is proportional to the fluctuation event probability within the current sector. Figure 1b, and 1c show a sample ROTI maps. These maps correspond to quiet (Fig. 16b, ΣKp = 3) and geomagnetically disturbed (Fig. 16c, ΣKp = 37) days in June 2012.

Fig. 16. Location of the processed GNSS stations (a) and ROTI maps for quiet (b) and disturbed (c) geomagnetic conditions

Data from the permanent GNSS network were used to develop the empirical model of the ionospheric irregularities over the Northern Hemisphere (Cherniak et al. 2014c). Daily dependences of the rate of TEC index (ROTI) as a function of geomagnetic local time on the specific grid were used as initial data. Correlation between the Kp geomagnetic index and parameters that characterized the activity of the ionosphere irregularities in 2010 to 2013 were investigated. Figure 17 presents the SBIR position for different values of the daily sum of geomagnetic indices Kp. Several intervals with different sums of Kp values were examined to construct the SBIR positions (indicated by red line). The solid black lines indicate the standard deviations of the calculated values.

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Vertical total electron content (vTEC) values computed using IRI-2012 and IRI Plas models have been compared with diurnal GPS vTEC data derived from European mid-latitude GPS station Potsdam (Zakharenkova et al. 2014b). Comparative data-model analysis does not reveal good performance in vTEC representation. It was found that new extension of IRI model – IRI Plas – cannot represent correctly the vTEC variations over European midlatitudes and mainly overestimates GPS vTEC especially for low and moderate solar activity (Zakharenkova et al. 2014a). In order to estimate the source of the data-model discrepancies, the case-study with detailed analysis of the model simulated electron density profiles was done. All models do not represent correctly the topside profile part and tend to overestimate the electron density higher than F2 peak. The main problem of the IRI vTEC representation is not situated in the plasmaspheric part, its absence in IRI model or its presence in IRI Plas model, the main source of the resulted discrepancies is still in the IRI topside ionosphere representation. Figure 18 presents: a) the comparison of IRI-2012 and IRI Plas electron density profiles for 1200 LT of December 2000, b) the comparison of IRI-2012, IRI Plas, NeQuick electron density profiles, ionosondes NmF2 and in situ CHAMP measurements for the same time and c) the comparison of GPS vTEC with vTEC derived by IRI-2012, IRI Plas, NeQuick models with different upper limit for EDP integration.

Fig. 17. Southern border of the ionospheric irregularities oval for different levels of geomagnetic activity

The ionosphere/plasmasphere electron content

(PEC) variations during strong geomagnetic storms in November 2004 were estimated by combining of mid-latitude Kharkov incoherent scatter radar observations and GPS TEC data derived from global TEC maps (Cherniak et al., 2014a). Two independent measurements were compared by analysis of the height-temporal distribution for specific location corresponding to the mid-latitudes of Europe. The percentage contribution of PEC to

GPS TEC indicated the clear dependence from the time with maximal values (more than 70%) during night-time. During day-time the lesser values (30–45%) were observed for quiet geomagnetic conditions and rather high values of the PEC contribution to GPS TEC (up to 90%) were observed during strong negative storm. These changes can be explained by the competing effects of electric fields and winds, which tend to raise the layer to the region with lower loss rate and movement of the ionospheric plasma to the plasmasphere.

Fig. 18. Comparison of IRI-2012 and IRI Plas electron density profiles for 1200 LT of December 2000 (a). Comparison of IRI-2012, IRI Plas, NeQuick electron density profiles, ionosondes NmF2 and in situ CHAMP measurements for the same time (b). Comparison of GPS vTEC with vTEC derived by IRI-2012, IRI Plas, NeQuick models with different upper limit for EDP integration (c)

Figure 19 shows the increasing of F2 layer peak

height afternoon in 9 November 2004, and ionospheric slab thickness values practically at the same time. The altitude of the F peak increased from 250 to >400 km before midnight of 9 November. At the noon of 10 November the hmF2 reached values of about 350 km, that essentially exceed hmF2 values for day-time during reference quite period.

Fig. 19. The EDP in the height range 100–1000 km for night and day time for the reference quiet period (typical) in 29 October 2004 and during the storm; the black cross indicates position of CHAMP PLP observations

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GNSS-based distance metrology

Surveyors and researchers in geosciences are recently facing the challenge of measuring distances over several hundreds of meters up to 1 kilometre with uncertainties at a single millimetre level and below. Electronic distance meters (EDMs) and GNSS are available for this task and long length metrology complies with GNSS-based short distance measurements. Both approaches, however, are currently not capable of achieving traceability to the SI definition of the metre with one or even sub-millimetre uncertainty over short distances. Uncertainty of GNSS-based distance metrology using EPN double stations data (Borowa Gora, Jozefoslaw, Lamkowko, Wettzell and Zimmerwald) were investigated by IGiK team in cooperation with UWM Olsztyn (Poland), Institute of Metrology, Kharkiv (Ukraine) and Institute of Radio Astronomy of NAS, Kharkiv (Ukraine) (Cisak et al., 2014). Numerical experiments conducted indicate that the potentiality of GNSS positioning is not fully exploited in high-end applications. Also, analysis of time series of GNSS solutions may result in improvement of modelling of GNSS observations and GNSS-based distance metrology.

3.6. Advanced methods for satellite positioning

Research on studies of stochastic properties of correction terms in GNSS Network RTK positioning was carried out at the Warsaw University of Technology (WUT). The effect of modelling of ionospheric and tropospheric refraction as well as orbit errors on reliability and accuracy of Network RTK performance was investigated. The stochastic model for Network RTK positioning, particularly dedicated to instantaneous solution based on a single epoch of GNSS observation has been developed (Prochniewicz, 2014). The numerical experiments on two test networks showed that the proposed method of stochastic modelling can increase the reliability of instantaneous Network RTK performance. Research on advanced methods for satellite positioning was continued at the University of Warmia and Mazury (UWM) in Olsztyn. It was focused on algorithm development for multi-frequency and multi-GNSS precise positioning (Paziewski and Wielgosz, 2014), analysis of the inter system biases (ISB) in multi-GNSS relative positioning, development of the regional ionosphere model based on carrier-phase data only (Krypiak-Gregorczyk et al., 2014), development of ionospheric MSTID warning service for Polish users (Krukowska et al., 2014), analysis of phase centre correction models for GNSS antennas, and testing of new automatic postprocessing module for ultra-fast static positioning (POZGEO-2) designed

for the ASG-EUPOS system (Paziewski et al., 2014).

4. ASG-EUPOS network

4.1. Status of the ASG-EUPOS network

At the end of 2014 the network of the ASG-EUPOS system consisted of 125 operating permanent reference stations (53 GPS/GLONASS stations) (Fig. 20) (www.asgeupos.pl).

Fig. 20. Reference stations of the ASG-EUPOS system (31 December 2014)

The number of changes in the ASG-EUPOS stations took place in 2014. Receiver and antenna have been replaced at 28 stations in northern and southern regions of Poland. Two stations have been moved to the new localizations: RWM1 station replaced RWMZ (Rawa Mazowiecka) station and GDA1 station replaced GDAN (Gdansk). Two stations CBKA (Warszawa) and OLST (Olsztyn) were excluded from the network RTK solution due to obsolete hardware. CBKA station is in addition temporarily (already second year) excluded from the system).

Since 12 July 2014 all services in ASG-EUPOS system are fully payable as a new act on geodetic and cartographic law was introduced into force (so far all services and data were available free of charge). Due to introduction of charges a total number of registered users dropped down from 14000 in June 2014 up to 5100 in December 2014. However, number of real time services users stabilized at the level of 3700 active licenses at the end of 2014.

In 2015 the modernization of ASG-EUPOS is to be continued and equipment replacement on another 35 stations is to planned. Additionally 2 new reference stations: OPNT (Olsztyn) and VSTT (Vištytis, Lithuania) are to be included into the network.

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5. Local GNSS networks

Besides the ASG-EUPOS three other GNSS permanent station networks in Poland are operating for commercial use. There are: TPI NET PRO (developed by TPI the local Topcon and Sokkia equipment reseller http://www.tpinet.pl) which encompasses nationwide distributed 118 stations, VRSNET.PL (developed by Geotronics Polska the local Trimble equipment reseller http://vrsnet.pl) which encompasses 21 stations located in NW part of Poland and Silesia region, and Leica SmartNet Poland (developed by Leica Geosystems Polska the local Leica equipment representative http://pl.smartnet-eu.com) which encompasses 120 stations distributed over whole territory of Poland.

6. Modelling precise geoid

The new gravimetric quasigeoid model GDQM-PL13 for Poland was developed. The 1'×1' mean Faye gravity anomalies, deflections of the vertical for the territory of Poland, gravity anomalies from the neighbouring countries and the EGM2008 were used as input data. The remove-compute-restore (RCR) method and the least squares collocation approach with the planar logarithmic covariance function of gravity anomalies were applied. Accuracy assessment of the GDQM-PL13 with the use of precise GNSS/levelling data proved its high quality. The fit of the geoid heights from GDQM-PL13 to the corresponding ones of 1st and 2nd order sites of GNSS/levelling control traverse, the EUVN, ASG-EUPOS, and POLREF networks sites represented by the standard deviations of respective differences is of 1.4 cm, 1.6 cm, 1.8 cm, 1.8 cm, and 2.2 cm, respectively. On the other hand the fit of geoid heights from the GDQM-PL13 to the corresponding ones from the gravimetric quasigeoid model GDQ08 developed in 2008 for the area of Poland (Fig. 21), EGM2008, and TIM RL05 in terms of the standard deviations is 1.1 cm, 1.6 cm, and 30 cm, respectively (Szelachowska and Krynski, 2014).

Fig. 21. Comparison of the GDQM-PL13 model with the GDQ08

The determination of an accurate geoid model remains an important challenge for geodetic research in Sudan. A new gravimetric geoid model SUD-GM2014 for the area of Sudan has been developed using recent released GOCE-based GGMs, available terrestrial mean free-air gravity anomalies and the high-resolution SRTM global digital elevation model. The computations of the SUD-GM2014 were performed using RCR procedure and the least squares collocation method. The residual terrain modelling (RTM) reduction method was applied to estimate the topography effect on the geoid. The resulting gravimetric geoid model has been evaluated using geoid heights at 19 GNSS/levelling points distributed over the country. The evaluation results and the expected quality of the SUD-GM2014 geoid model were discussed considering the quality of GNSS/levelling data in Sudan. The SUD-GM2014 or the geoid model computed from GOCE-based GGMs only has been recommended as reference for GNSS heighting in Sudan (Godah and Krynski, 2014).

A new gravimetric geoid model has been developed for Brunei with the use of terrestrial and airborne gravity data as well as altimetry data. The computation of the model was performed using the least squares collocation method and remove-compute-restore procedure with the EGM08 global geopotential model. The estimated accuracy of the gravimetric geoid for the territory of Brunei is at the level of 0.3 m. The geoid model developed shows poor quality of the existing GPS/levelling data in Brunei (Table 6) that indicates poor quality of local vertical datum (Lyszkowicz et al., 2014).

7. The use of data from satellite gravity missions

The quality of 4th and 5th release GOCE-based global geopotential models (GGMs) were extensively investigated in IGiK. They were evaluated together with the EGM2008 over the area of Poland using high precision GNSS/levelling data. It has been shown that the accuracy of 2.1–3.3 cm of height anomalies obtained from 4th release GOCE-based GGMs at maximum d/o 200 could be expected at any place on the Earth, except the poles and their adjacent areas that were not flown over by the GOCE satellite (Godah et al., 2014a). The fit of the EGM08 and 5th release GOCE-based GGMs in terms of gravity anomalies, measured with a standard deviation is 1.71 mGal, and 1.75-1.80 mGal, respectively (Godah et al., 2014b).

The contribution of GOCE mission to the long/medium wavelength component (approximately 100 km half wavelength spatial resolution) of the Earth gravity field was investigated for the area of Poland (a very good coverage of high quality terrestrial gravity data and GNSS/levelling data) and a sub-region of East

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Africa (poor terrestrial gravity data coverage and only a few GNSS/levelling points) by the team of IGiK (Godah et al., 2014c). On the basis of the combination of recently released GOCE-based GGMs and local terrestrial gravity data, gravimetric geoid models for the area of Poland as well as for the area of Sudan were developed using least squares collocation method. GOCE data does not improve the EGM2008 in Poland but GOCE-based GGMs can be used as independent source for detection outliers in gravity functionals in Poland. On the other hand GOCE-based GGMs can substantially improve local gravimetric geoid models in the areas of lacking uniform terrestrial gravity data coverage, e.g. a sub-region of East Africa.

The results of studies on GOCE-based GGMs conducted over the area of Poland have efficiently been applied in IGiK for the assessment of the GOCE GGMs over the area of Sudan. In particular, the 3rd release GOCE-based GGMs were compared in Sudan with the terrestrial gravity and GNSS/levelling data. The GOCE-derived free-air gravity anomalies and height were found consistent with the respective terrestrial ones within the range from 4.9 to 5.6 mGal, and 64 cm, respectively (Godah and Krynski, 2015).

Research on the use of GRACE solutions was conducted in 2014 in cooperation of UWM in Olsztyn and the Space Research Centre of the Polish Academy of Sciences (Nastula et al., 2014). Compatibility of gravimetric functions with hydrological signal in observed geodetic excitation function of polar motion were examined. The best result based on the agreement between gravimetric-hydrological excitation functions and geodetic residuals was obtained for the χ2 component of gravimetric excitation function computed from the CSR, Tongji and CNES data series.

The use of satellite missions for local hydrological conditions study was investigated. The hydrological, meteorological and GRACE GGMs were evaluated and their use for local hydrosphere condition, in particular for flood and drought prediction was assessed. Meteorological land hydrosphere models were processed through an appropriate optimal filtration, and then scaled to the level of GRACE models. The combined GRACE and hydrosphere model was developed (Birylo et al., 2015a). The model has been extended by data on infiltration and water absorbing characteristics of the soil (Birylo et al., 2015b).

8. Earth tides monitoring

Earth tides were continued to be monitored in 2014 at the Borowa Gora Observatory of IGiK with the LCR G1036 gravimeter equipped with the LRFB-300 feedback system (Fig. 22).

Fig. 22. Gravity record with LCR-G gravimeter in Borowa Gora Observatory averaged in 1 hour window

The first complete tidal analysis of 745 days of gravimetric recordings from 2012, 2013 and the beginning of 2014 at the Borowa Gora Observatory was performed in early 2014 (Dykowski and Sękowski, 2014). For the tidal analysis multiple calibrations of the LCR G1036 with the use of absolute gravimeters FG5-230 and A120-020 were performed. For the tidal analysis the HW95 tidal catalogue was used along with Wahr-Dehant inelastic Earth model. Results for the determined tidal components were calculated for a 5 minute and 1 hour data (Fig. 23).

Fig. 23. Tidal factors (top) and phase leads (bottom) for the local model

The calculated standard deviations are visibly

different; they reach 2.9 nm/s2 and 5.0 nm/s2 for 1 hour and 5 minute solutions, respectively. Model fit residuals for the analysis is shown in Figure 24, presenting the quality of the evaluated tidal model. The achieved standard deviation for the final solution equal to 2.9 nm/s2 is consistent with values estimated for other spring gravimeters.

Fig. 24. Adjustment residuals for a 5 min and 1h tidal records data

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9. Activity in Satellite Laser Ranging

In the year 2014 satellite laser ranging system at the Borowiec SLR station (SOD 78113802) was modernized. A new optic system was replaced in the receiving telescope, including primary and secondary mirrors as well as special dielectric mirrors transferring laser pulse from laser unit to the telescope (Fig. 25).

Fig. 25. A new dielectric mirror of optical canal

The second step of modernization concerned lasers. Two laser modules were installed, the standard unit (Lithuanian EKSPLA PL-2250) used for laser tracking of all ILRS 47 satellites listed at http://ilrs.gsfc.nasa.gov/missions/satellite_missions/current_missions/ and high-energy module (American Continuum Surelite III) dedicated to laser tracking of space debris. In addition, a high speed start Si photodiode FDS025 working in the range from 400 to 1100 nm was installed.

The analysis of the station positions and velocities determined from SLR and GNSS was continued in 2014. The differences between from SLR and GNSS solutions are at the level of 5-10 mm for station positions and at the level of 0.5 mm/year for velocities. The fulfilment of expected by GGOS accuracy level of 1 mm in position and 0.1 mm/year in velocity will be difficult to achieve in the next years.

Time series of solutions for SLR and GNSS stations located close to each other can efficiently be used for mutual control of coordinates. The analysis of such time series can also be used to estimate the quality of local ties, which are crucial for the maintenance of global reference frame (Szafranek et al., 2014).

Time series of SLR and GNSS stations coordinates were also used for the determination of long-term dependencies on selected GNSS-SLR co-located sites. The annual signals in N,E,U components were examined using least-squares and the amplitudes and phase shifts for both types of observations were compared. The amplitudes vary from 1 to 21 mm, while phase shifts are unevenly

distributed over the seasons. The wavelet decomposition method with the use of symmetric and orthogonal Meyer wavelet was also applied (Bogusz et al., 2014a). Besides the significant annual and semi-annual frequencies, the periods of 0.85, 3 and 4 cpy with the amplitudes of more than 0.5 mm for GNSS and 3 mm for SLR techniques were removed. The noise analysis with MLE method showed amplitudes of several millimetres with spectral indices between -1 and 0, and -1.3 and 0.7, for GNSS and SLR solutions, respectively. The GNSS and SLR techniques do not show the same noise characteristics (Bogusz et al., 2014b).

10. Geodynamics

Extended research on geocenter motion was conducted in 2014. The spectra-temporal wavelet semblance with application of the modified Morlet wavelet function enables computation of correlation coefficients between the time series of the centre of mass of the Earth determined by DORIS, GNSS and SLR techniques as a function of time and frequency. These 3D time series were projected into the planes of ITRF to get three complex-valued time series for each technique in each plane. The highest positive semblance values occur in the XY equatorial plane for the retrograde annual oscillation in the GNSS and SLR data as well as prograde annual oscillation between DORIS and other two techniques. The spectra-temporal semblance functions in YZ plane between the geocenter time series from SLR and other two techniques show annual prograde oscillation (Kosek et al. 2014).

The wavelet based semblance filtering was applied to the complex-valued projections of the 3D centre of mass time series of the space geodetic techniques. It was found that there exists a common retrograde annual oscillation in the equatorial plane between the GNSS and SLR geocenter time series with amplitude of the order of 2-3 mm and this oscillation is out of phase between DORIS and two other techniques (Kosek et al., 2014; Wnęk et al., 2014). The common signals computed by the wavelet based semblance filtering in the geocenter coordinates which is constructed using lower frequency components enable the determination of the smoothed geocenter time series model (Fig. 26) (Kosek et al. 2014).

To find geophysical interpretation of the geocenter motion model the geophysical coordinates of the geocenter constructed from the first degree gravity coefficients determined from GRACE as well as 2nd and higher order coefficients determined from atmospheric and ocean angular momentum functions were considered. The specra-temporal semblance functions between the geocenter motion model obtained from space geodetic techniques and geophysical geocenter

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motion model show the highest positive correlation for the retrograde annual oscillation in the XY plane as well as prograde annual oscillation in the YZ plane of the ITRF (Wnęk et al., 2014).

Fig. 26. The model center of mass time series (bold) computed as the average of the GNSS (gray) and SLR (dotted) common oscillations composed of only 6 lower frequency components together with the filtered oscillations (Kosek et al., 2014)

Recent tectonic activity in the area of Swiebodzice Depression is recorded by the instruments of the underground Geodynamic Laboratory (GL) of the Space Reseach Centre, Polish Academy of Sciences (SRC PAS). Indications of tectonic activity such as tiltings of foundation and vertical motions are repeatedly observed by water-tube tiltmeters (WT). The effects of tectonic activity in the region of Ksiaz are visible in the geological structure of the orogen as well as deformations of Pelcznica Valley meander (Fig. 27) (Zdunek et al., 2014).

Fig. 27. Time series of KSIA-KSI1 vector components for the period of 1.36 years (from 2013:139 to 2014:270)

Zones of discontinuity in the environment of underground laboratory as well as objects of the castle were determined by geodetic measurements at established geodetic horizontal network and precise geological and structural identification. Simultaneously, works on identifying damages of Ksiaz castle architectural objects were conducted, the appearance of which suggested connection with the activity of tectonic faults (Kasza et al., 2014).

High accuracy of gravity determination with the modern absolute and superconducting gravimeters requires the use of an accurate model of

atmospheric impact on gravity. Different methods of computing the atmospheric gravity effects including the classic statistical approach, as well as methods which reflect physical phenomena of the variable atmosphere mass distribution has been presented (Rajner, 2014). The latter uses the surface or spatial distribution of meteorological parameters from numerical weather models. The usefulness of physical methods was verified in numerical experiments with the use of gravimetric data acquired at the Warsaw University of Technology and data from the Global Geodynamics Project. The results showed that using the complex method is crucial if the microgal level of accuracy is required. This is especially important when periods of several months and longer are considered.

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