Borowa Góra Geodetic and Geophysical Observatory
- Historical overview
The origins of the Borowa Góra Geodetic and Geophysical Observatory date back to 1929, when a uniform geodetic system was being created in the reborn Polish state. One of the points of intersection of the meridian and parallel chains of the triangulation established at that time, located on the site of today’s Observatory, was adopted as the central astronomical point for the new measurement of the country. The first determination of the astronomical longitude difference between the Borowa Góra Observatory and the Paris Astronomical Observatory was made in 1929 by Dr. Antoni Czeczot from the Ministry of Public Works and Dr. Jan Krassowski from the Military Geographical Institute, using newly purchased transitional instruments from Askania Werke. In 1930, the astronomical latitude of the point and the astronomical azimuth of Borowa Góra – Modlin were determined.
The Borowa Góra point became the basic point of the state astronomical and geodetic network as the point of application of the Bessel ellipsoid to the geoid and the beginning of the coordinate system called the “Borowa Góra” system. The orientation of the ellipsoid was determined using the azimuth to the water tower in Modlin. The coordinates of the point of application (latitude and longitude) resulting from astronomical measurements were adopted:
φ = 52°28’32.85“ λ = 21°02’12.12”
In 1936, a reinforced concrete tripod was erected over this point and covered with earth to form a 7 m high mound. In the same year, a three-legged concrete tower was also built to suspend a plumb line when testing the perpendicularity of the horizontal axis to the vertical axis of instruments designed to measure azimuth. A fundamental benchmark with the catalog number 26310023 was also stabilized on the Observatory grounds. In 1937, the Observatory building was constructed.
The war period from 1939 to 1944 brought enormous damage and destruction to the Observatory. The occupiers took away all the instruments, and the building was used as a German military post supervising the nearby border between the General Government and the Reich. In 1944, as the front passed through, the building, garden, and mound above the main point were destroyed, and gravel was extracted from the Observatory grounds.
In 1945, the Observatory was taken over by the Main Office of Land Surveying. The area was restored, the building and concrete pillars for astronomical and geodetic instruments were rebuilt. The earth-concrete structure above the main triangulation point was renovated. In 1951, a Zeiss Jena transitional instrument was purchased for use in measurements at Laplace points. However, this instrument was soon replaced by a Wild T4 and AU 2/10 astronomical theodolite. The transitional instrument was used for special measurements as part of international cooperation.
In 1952, the Observatory was transferred to the Geodetic Scientific Research Institute (now the Institute of Geodesy and Cartography) as a base for conducting research necessary for the work carried out by the Office. In 1952–54, the Observatory conducted training courses for astronomical observers at Laplace points. Between 1955 and 1958, the Observatory’s instruments and equipment were significantly expanded in connection with the Observatory’s participation in an international campaign to determine differences in longitude related to the Geophysical Year. Among other things, precise pendulum clocks were installed, initially by Leroy and then by Shortt. A second Observatory building was also constructed.
Since 1957, preparations have been underway for the Observatory to provide time services. The Observatory was equipped with two quartz clocks, a printing chronograph, a time signal receiver, a flash chronoscope, and other devices to secure the power supply system. The contact micrometer was replaced with a photoelectric recorder in the transition instrument. In January 1963, the Observatory joined an international program to study irregularities in the Earth’s rotation, systematically sending its observations to the International Bureau of Weights and Measures (BIPM) in Paris, the Pole Motion Research Center (IPMS) in Mizusawa, to the Institute of Physical and Technical Measurements and Radio Engineering (WNIIFTRI) in Moscow, and to the Astronomical Observatory in Shanghai. Read more
The early 1970s brought a technical revolution in geodesy in the form of the use of artificial satellite observations to determine positions. The Borowa Góra Observatory installed an AFU75 camera borrowed from the USSR and purchased an Ascorecord from Zeiss Jena for processing photographic observations of satellites. Photographic observations of SSZ were conducted until 1977, participating in campaigns of the Socialist Countries. Photographic observations replaced Doppler observations of the TRANSIT system. Initially, the observations were carried out on behalf of Geokart using a JMR receiver, and from 1986, the Observatory was equipped with a Polish-made DOG3 receiver, which operated until 1990 – the end of the TRANSIT system. In 1991, Ashtech GPS surveying receivers were purchased. In 1996, permanent GPS observations were launched at the Observatory. The station, which was included in the European Permanent Network (EPN), was assigned the number 12207M002 and the code name BOGO. Five years later, permanent observations of two systems, GPS and GLONASS, were launched at the EUREF-POL 0217 point. The station was given the number 12207M003 and the code name BOGI; it was included in the International GNSS Service (IGS) network and also in the EPN. Read more
With the establishment of the BOGI station, an automatic weather recording station was launched. The recorded values of temperature, humidity, and atmospheric pressure are collected in the IGiK database and sent in RINEX format together with GNSS observations to Local Computing Centers in Graz, Frankfurt, and Warsaw. Read more
In 1995, in cooperation with CBK PAN, continuous recording of gravitational acceleration and groundwater level was launched at the Observatory. The tide station, assigned the number 0908, was included in the international network of tide stations of the International Association of Geodesy, coordinated by the Royal Observatory of Belgium. Unfortunately, the need to return the tidal gravimeter to CBK in 1997 interrupted the collection and processing of tidal data. Continuous recording resumed in 2011, adapting one of the LaCoste&Romberg gravimeters with electronic recording. Read more
In 2008, the Institute of Geodesy and Cartography purchased an A10 field absolute gravimeter, serial number 20, from Micro-g LaCoste for research and implementation purposes. The gravimeter and its equipment were placed in the Gravimetric Research and Calibration Laboratory at the Observatory.
In 1999–2000, a reference length base for checking and calibrating electromagnetic rangefinders was built at the Observatory. Due to the limited space, an innovative design and method of measuring the base was developed. Read more
The Observatory conducts permanent observations of the components of the Earth’s magnetic field intensity vector. The history of magnetic observations dates back to the 1950s, when a basement for magnetic measurements was built along with the extension of the building and basements. The laboratory and magnetic equipment were expanded in 2011–2013.
- Astrometric observations
Regular astrometric observations began in 1963 and continue to this day. Their main purpose is to study local changes in the direction of the vertical line. Based on observations of the time of passage of stars through the local meridian, time differences (TU1 – TUC) for Borowa Góra are calculated and compared with the differences (TU1 – TUC) published by the IERS (International Earth Rotation and Reference Systems Service). Analysis of the results obtained so far allows us to determine periodic expressions in the course of these differences, as well as a certain long-term trend. The observations are made with a Zeiss transit instrument with a photoelectric recorder. The moments when stars pass through successive slits of the photoelectric device just before and after the local meridian are recorded on a computer disk in relation to the rubidium clock time scale. The observation program consists of 24 groups of stars, with 10–11 stars in each group. On each clear evening, 1 to 3 groups are observed. The numbers of the observed groups depend on the season.
Number of observation series performed in 2006–2014
- GNSS
In 1991, Ashtech GPS receivers were purchased. In 1996, permanent GPS observations were launched at the Observatory. The station, which was included in the European Permanent Network (EPN), was assigned the number 12207M002 and the code name BOGO. Five years later, permanent observations of two systems, GPS and GLONASS, were launched at the EUREF-POL 0217 point. The station was given the number 12207M003 and the code name BOGI; it was included in the International GNSS Service (IGS) network and the EPN.
Graphs of N, E, Up coordinates recorded by the BOGO station between 1996 and 2015
Graphs of N, E, Up coordinates recorded by the BOGI station between 2001 and 2015
More information about the BOGO and BOGI stations can be found on the EPN website:
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- Weather station
With the establishment of the BOGI station, an automatic weather recording station was launched. The recorded values of temperature, humidity, and atmospheric pressure are collected in the IGiK database and sent in RINEX format together with GNSS observations to Local Computing Centers in Graz, Frankfurt, and Warsaw.
At http://bg.igik.edu.pl:11180/meteo/, you can view graphs of recorded temperature, relative and absolute humidity, soil moisture, groundwater level, and local pressure over the last two days, while at http://bg.igik.edu.pl: 11180/piezometer/ you can find graphs comparing the piezometer readings with the barometer readings.
Sample temperature recording graph
Sample humidity recording graph
Sample soil moisture recording graph
Sample groundwater level recording graph
Sample atmospheric pressure recording graph
Sample graphs comparing piezometer readings with barometer readings
- Gravimetry
Currently, three L&R G gravimeters are installed at the Observatory, permanently recording changes in gravitational acceleration. An example of the course of changes is shown in the graph below.
The records from the tidal gravimeters for the last two days can be viewed at:
L&R 1036: http://bg.igik.edu.pl:11180/LR1036/
L&R 1012: http://bg.igik.edu.pl:11180/LR1012/
L&R 1084: http://bg.igik.edu.pl:11180/LR1084/
In 2008, the Institute of Geodesy and Cartography purchased an A10 field absolute gravimeter, serial number 20, manufactured by Micro-g LaCoste, for research and implementation purposes. The gravimeter and its equipment were placed in the Gravimetry Research and Calibration Laboratory at the Observatory.
- Broken Length Base
Between 1999 and 2000, a reference length base for checking and calibrating electromagnetic rangefinders was built at the Observatory. Due to limited space, an innovative design and measurement method for the base was developed.
The base was built in two stages. In the first stage, which was completed in October 1999, five poles marked A, B, C, 1, and 2 were stabilized.
In the second stage, completed in early spring 2000, four more poles marked D, D”, 3, and 4 were stabilized.
Test measurements and calibrations of the ŁBD were performed using a Leica TC2002 precision total station in June and September 2000 and in April 2001.
In 2008, as a result of the construction of an expressway running through Borowa Góra, IGiK was forced to hand over the north-western part of the Observatory’s area for the construction of the new route. For this reason, two base pillars were lost: the C break point pillar and the D” end pillar.
According to the new design, pole No. 4 (after the reconstruction of the head, which involved concreting a centering plate on it) became the new break point C. In addition, three new base points were designed, marked according to the new point numbering as 1, 4, and 6.
- Geomagnetism
Since 2005, the Borowa Góra Observatory has been recording the X, Y, and Z components of the geomagnetic field intensity vector. The LEMI magnetometer, recorder, and probe are located in a magnetic mound (Fig. 1) in the southern part of the Observatory grounds.
The course of recording changes in the X, Y, and Z components of the geomagnetic field intensity vector carried out in the magnetic mound can be followed on the Internet at http://rtbel.igf.edu.pl/. After entering the website, select the BGA – Borowa Góra observatory from the list available under the Selection of magnetograms tab (Fig. 2).
Fig. 1 Magnetic mound
Fig. 2. An example of the recording of the X, Y, and Z components of the geomagnetic field vector at the Borowa Góra Observatory against the background of the recording from the Central Geophysical Observatory of the Institute of Geophysics of the Polish Academy of Sciences in Belsk, together with the selection form
The record of the magnetometer readings from the mound from the last two days can also be followed at http://bg.igik.edu.pl:11180/magnetometr/. An example of the recording of the X, Y, Z components at the Borowa Góra Observatory is shown in Fig. 3.
Fig. 3 Example of the recording of the X, Y, Z components of the geomagnetic field intensity vector at the Borowa Góra Observatory
Next to the magnetic mound at the Borowa Góra Observatory, there is a base point (Fig. 4) where absolute measurements of the magnetic field components D, I, and F are taken to determine the X, Y, and Z bases. In 2011, the base point was permanently stabilized and enclosed. The magnetic pavilion (Fig. 5) around the base point was constructed from coniferous square timber without the use of materials that interfere with the magnetic field and was protected with impregnating agents.
Fig. 4. Magnetic base point
Control measurements of the total F component of the magnetic field intensity before and after construction showed no changes in the gradient. In addition, a point (marker) was stabilized at the Observatory using a disc to indicate true north, clearly visible from the window of the magnetic pavilion.
Fig. 5. Magnetic pavilion
A 0.5 × 0.5 × 0.4 m pit was dug 5 m west of the pavilion, concreted and protected against large temperature fluctuations or the influence of other meteorological phenomena. It serves as a station for a magnetic probe duplicating the work of the probe in the magnetic mound. The recording of magnetic field changes in the pavilion will be interrupted as needed for field work.
In May 2012, after prior testing, a new type of magnetic field change recorder was installed in the magnetic mound. It allows direct monitoring of geomagnetic field changes on a computer in a network or on the Internet. The recorder can be controlled via the network.
