Proceedings of the 5th Joint International Symposium on Deformation Monitoring - JISDM 2022
VLBI telescope reference point, the closest point in the telescope primary axis from the secondar... more VLBI telescope reference point, the closest point in the telescope primary axis from the secondary axis, is typically determined indirectly by observation of points co-rotating with the telescope. We have previously measured telescope reference point indirectly with two GPS-antennas attached on the edge of the dish of the Aalto University Metsähovi radio telescope in 2008-2015. Now we have applied the same technique to the new VGOS-telescope of the FGI Metsähovi geodetic research station. The reference point of the VGOS antenna was estimated using post-processed trajectory coordinates of two GNSS antennas. The antennas are attached on the edge of the radio telescope dish with gimbals where a counterweight with shock absorber act as compensators to ensure zenith pointing at all telescope elevation angles. In addition, spherical prisms are attached to the structure of the telescope for tachymetric reference point determination. One purpose of this study is to evaluate the limit values...
We provide a survey on the joint European research project “GeoMetre”, which explores novel tech... more We provide a survey on the joint European research project “GeoMetre”, which explores novel technologies and their inclusion to existing surveying strategies to improve the traceability of geodetic reference frames to the SI definition of the metre. This work includes the development of novel distance meters with a range of up to 5 km, the realisation of optical multilateration systems for large structure monitoring at an operation distance of 50 m and beyond, and a novel strategy for GNSS-based distance determination. Different methods for refractivity compensation, based on classical sensors, on dispersion, on spectroscopic thermometry, and on the speed of sound to reduce the meteorological uncertainties in precise distance measurements, are developed further and characterised. These systems are validated at and applied to the novel European standard baseline EURO5000 at the Pieniny Kippen Belt, Poland, which was completely refurbished and intensely studied in this project. We us...
Proceedings of the 5th Joint International Symposium on Deformation Monitoring - JISDM 2022
Deformation monitoring requires the detection of smallest changes, always at the limits of techni... more Deformation monitoring requires the detection of smallest changes, always at the limits of technical feasibility. Trying to push these limits further, we have realised two terrestrial ranging instruments: a long-range 1D electro-optic distance meter and a 3D multilateration-capable sensor system of 50 m range. The former one is intended as primary standard for the calibration of geodetic instrumentation with low uncertainty to the SI definition of the metre. The latter one is intended for monitoring larger monuments like VLBI antennas. In this contribution, we describe the technical challenges and our solutions for such instrumentation. We use the two-colour method for inline refractive index compensation. As common optical source, we developed a versatile multi-wavelength generator based on two Nd:YAG lasers stabilised by a phase-locked loop realised by Field Programmable Gate Arrays (FPGA). The 1D interferometer uses custom-designed achromatic optics and a mechanical frame optimis...
In a joint effort, experts from measurement science and space-geodesy develop instrumentation and... more In a joint effort, experts from measurement science and space-geodesy develop instrumentation and methods to further strengthen traceability to the SI definition of the metre for geodetic reference frames (GRF). GRFs are based on space-geodetic observations. Local-tie surveys at co-location sites play an important role for their computation. Novel tools are hence developed for reference point monitoring, but also for local tie vector determination and ground truth provision. This contribution reports on the instrumental approaches and achievements after 24 months project duration and discusses the remaining work in the project.
The datum problem is a fundamental issue in the network adjustment when connecting a local measur... more The datum problem is a fundamental issue in the network adjustment when connecting a local measurement network to an external reference frame. Datum elements in 3D networks are scale, translation, and orientation. We consider here the local tie network at geodetic core stations, where the external reference frame is the latest ITRF realization, ITRF2014, in the mean epoch of terrestrial observations.Accurate distance measurements are used for the determination of the network scale. Thus the improvement of its accuracy and the inclusion of weather measurements to account for refraction errors are essential. For rotation and translation of the network, we need external information. Angle observations are related to the coordinate system of the instrument (e.g. a tachymeter) which is usually aligned to the plumb line. Instruments have different vertical orientation at every station point and the direction of the plumb line does not coincide with the normal vector of the reference ellip...
We have used GPS-based local-tie measurements simultaneously with geo-VLBI observations since 200... more We have used GPS-based local-tie measurements simultaneously with geo-VLBI observations since 2008 during every geodetic VLBI session at Metsähovi. This system uses gimbal-mounted GNSS antennas that are mounted on the reflector of the Metsähovi 14-m radio telescope. A similar system was installed in 2013 at the Onsala 20-m radio telescope and has been used for a large number of VLBI sessions, including, e.g., the 15-day-long CONT14 campaign. In order to verify the results of the two systems, we performed a dedicated measurement campaign in the framework of the SIB60 project, involving both Metsähovi and Onsala. During this campaign the local ties at the two stations were measured simultaneously during two VLBI sessions in August and September 2015 where both stations participated. The robot tacheometer monitoring system HEIMDALL was used for the automated classical monitoring of the telescopes at both stations. Moreover, additional local terrestrial measurements were performed sever...
A new VGOS telescope will be built at the Metsähovi Geodetic Fundamental Station. We present here... more A new VGOS telescope will be built at the Metsähovi Geodetic Fundamental Station. We present here our plans concerning the VGOS project. Also we give an overview of the instruments located at the Metsähovi Geodetic Fundamental Station.
International Association of Geodesy Symposia, 2015
Based on the current state of technology, distance measurements over a few hundred metres in air ... more Based on the current state of technology, distance measurements over a few hundred metres in air with relative uncertainties significantly better than 10−6 are still an almost impossible challenge. In the European Joint Research Project (JRP) “Metrology for long distance surveying” measurement uncertainties in GNSS-based and optical distance metrology are going to be thoroughly investigated, novel technologies and primary standards developed and guidelines to improve surveying practice in the field worked out. A better understanding and a decrease of measurement uncertainty is also targeted for the critical local tie measurement at geodetic fundamental stations.
The phase center variation and the mean phase cente r of the GNSS antenna can be determined in th... more The phase center variation and the mean phase cente r of the GNSS antenna can be determined in the robot calibration. We have studied how well the offset values are valid in the field and the consistency between two sets of antennas of dif ferent type. We measured 24 full 48-hour-sessions in our relativ e GNSS antenna field calibration test at Metsähovi fundamental station during three months i n summer 2011. We chose the full roving observation strategy (Banyai 2005) and circu lated nine Ashtech Choke Ring antennas without radome and eight Leica AR25 antennas with r adome on three concrete pillars. Data were processed with Bernese GPS Software ver. 5.0 a nd offset estimation was coded using Octave software. In the Bernese processing we used the Geo++ absolute calibration offset values but in combining the 24 session solutions we still found significant antenna dependent offsets especially in L2 solution between the two a ntenna types. The offset values of the individual absolute ca...
Within the European Metrology Research Programme (EMRP) joint research project “Metrology for lon... more Within the European Metrology Research Programme (EMRP) joint research project “Metrology for long distance surveying” the Finnish Geospatial Research Institute (FGI) is advancing the work for new measurement methods, uniform scale and improved metrological traceability. The FGI measured its Nummela Standard Baseline using the Väisälä Interference Comparator in 2013. The measurement continues the time series of nearly 70 years, during which the variation of the 864 123 mm total length has remained smaller than 0.7 mm. The result is traceable to the SI unit metre, and the expanded uncertainty is 0.2 mm. The new results provide comparison data for validation of novel surveying instruments within EMRP, and the scale from Nummela also has been transferred to a network of pillars at Metsähovi fundamental station and for comparisons to other European geodetic baselines. A metrologically optimum processing strategy for short GPS baselines has been studied. Different antenna calibrations, n...
Proceedings of the 5th Joint International Symposium on Deformation Monitoring - JISDM 2022
VLBI telescope reference point, the closest point in the telescope primary axis from the secondar... more VLBI telescope reference point, the closest point in the telescope primary axis from the secondary axis, is typically determined indirectly by observation of points co-rotating with the telescope. We have previously measured telescope reference point indirectly with two GPS-antennas attached on the edge of the dish of the Aalto University Metsähovi radio telescope in 2008-2015. Now we have applied the same technique to the new VGOS-telescope of the FGI Metsähovi geodetic research station. The reference point of the VGOS antenna was estimated using post-processed trajectory coordinates of two GNSS antennas. The antennas are attached on the edge of the radio telescope dish with gimbals where a counterweight with shock absorber act as compensators to ensure zenith pointing at all telescope elevation angles. In addition, spherical prisms are attached to the structure of the telescope for tachymetric reference point determination. One purpose of this study is to evaluate the limit values...
We provide a survey on the joint European research project “GeoMetre”, which explores novel tech... more We provide a survey on the joint European research project “GeoMetre”, which explores novel technologies and their inclusion to existing surveying strategies to improve the traceability of geodetic reference frames to the SI definition of the metre. This work includes the development of novel distance meters with a range of up to 5 km, the realisation of optical multilateration systems for large structure monitoring at an operation distance of 50 m and beyond, and a novel strategy for GNSS-based distance determination. Different methods for refractivity compensation, based on classical sensors, on dispersion, on spectroscopic thermometry, and on the speed of sound to reduce the meteorological uncertainties in precise distance measurements, are developed further and characterised. These systems are validated at and applied to the novel European standard baseline EURO5000 at the Pieniny Kippen Belt, Poland, which was completely refurbished and intensely studied in this project. We us...
Proceedings of the 5th Joint International Symposium on Deformation Monitoring - JISDM 2022
Deformation monitoring requires the detection of smallest changes, always at the limits of techni... more Deformation monitoring requires the detection of smallest changes, always at the limits of technical feasibility. Trying to push these limits further, we have realised two terrestrial ranging instruments: a long-range 1D electro-optic distance meter and a 3D multilateration-capable sensor system of 50 m range. The former one is intended as primary standard for the calibration of geodetic instrumentation with low uncertainty to the SI definition of the metre. The latter one is intended for monitoring larger monuments like VLBI antennas. In this contribution, we describe the technical challenges and our solutions for such instrumentation. We use the two-colour method for inline refractive index compensation. As common optical source, we developed a versatile multi-wavelength generator based on two Nd:YAG lasers stabilised by a phase-locked loop realised by Field Programmable Gate Arrays (FPGA). The 1D interferometer uses custom-designed achromatic optics and a mechanical frame optimis...
In a joint effort, experts from measurement science and space-geodesy develop instrumentation and... more In a joint effort, experts from measurement science and space-geodesy develop instrumentation and methods to further strengthen traceability to the SI definition of the metre for geodetic reference frames (GRF). GRFs are based on space-geodetic observations. Local-tie surveys at co-location sites play an important role for their computation. Novel tools are hence developed for reference point monitoring, but also for local tie vector determination and ground truth provision. This contribution reports on the instrumental approaches and achievements after 24 months project duration and discusses the remaining work in the project.
The datum problem is a fundamental issue in the network adjustment when connecting a local measur... more The datum problem is a fundamental issue in the network adjustment when connecting a local measurement network to an external reference frame. Datum elements in 3D networks are scale, translation, and orientation. We consider here the local tie network at geodetic core stations, where the external reference frame is the latest ITRF realization, ITRF2014, in the mean epoch of terrestrial observations.Accurate distance measurements are used for the determination of the network scale. Thus the improvement of its accuracy and the inclusion of weather measurements to account for refraction errors are essential. For rotation and translation of the network, we need external information. Angle observations are related to the coordinate system of the instrument (e.g. a tachymeter) which is usually aligned to the plumb line. Instruments have different vertical orientation at every station point and the direction of the plumb line does not coincide with the normal vector of the reference ellip...
We have used GPS-based local-tie measurements simultaneously with geo-VLBI observations since 200... more We have used GPS-based local-tie measurements simultaneously with geo-VLBI observations since 2008 during every geodetic VLBI session at Metsähovi. This system uses gimbal-mounted GNSS antennas that are mounted on the reflector of the Metsähovi 14-m radio telescope. A similar system was installed in 2013 at the Onsala 20-m radio telescope and has been used for a large number of VLBI sessions, including, e.g., the 15-day-long CONT14 campaign. In order to verify the results of the two systems, we performed a dedicated measurement campaign in the framework of the SIB60 project, involving both Metsähovi and Onsala. During this campaign the local ties at the two stations were measured simultaneously during two VLBI sessions in August and September 2015 where both stations participated. The robot tacheometer monitoring system HEIMDALL was used for the automated classical monitoring of the telescopes at both stations. Moreover, additional local terrestrial measurements were performed sever...
A new VGOS telescope will be built at the Metsähovi Geodetic Fundamental Station. We present here... more A new VGOS telescope will be built at the Metsähovi Geodetic Fundamental Station. We present here our plans concerning the VGOS project. Also we give an overview of the instruments located at the Metsähovi Geodetic Fundamental Station.
International Association of Geodesy Symposia, 2015
Based on the current state of technology, distance measurements over a few hundred metres in air ... more Based on the current state of technology, distance measurements over a few hundred metres in air with relative uncertainties significantly better than 10−6 are still an almost impossible challenge. In the European Joint Research Project (JRP) “Metrology for long distance surveying” measurement uncertainties in GNSS-based and optical distance metrology are going to be thoroughly investigated, novel technologies and primary standards developed and guidelines to improve surveying practice in the field worked out. A better understanding and a decrease of measurement uncertainty is also targeted for the critical local tie measurement at geodetic fundamental stations.
The phase center variation and the mean phase cente r of the GNSS antenna can be determined in th... more The phase center variation and the mean phase cente r of the GNSS antenna can be determined in the robot calibration. We have studied how well the offset values are valid in the field and the consistency between two sets of antennas of dif ferent type. We measured 24 full 48-hour-sessions in our relativ e GNSS antenna field calibration test at Metsähovi fundamental station during three months i n summer 2011. We chose the full roving observation strategy (Banyai 2005) and circu lated nine Ashtech Choke Ring antennas without radome and eight Leica AR25 antennas with r adome on three concrete pillars. Data were processed with Bernese GPS Software ver. 5.0 a nd offset estimation was coded using Octave software. In the Bernese processing we used the Geo++ absolute calibration offset values but in combining the 24 session solutions we still found significant antenna dependent offsets especially in L2 solution between the two a ntenna types. The offset values of the individual absolute ca...
Within the European Metrology Research Programme (EMRP) joint research project “Metrology for lon... more Within the European Metrology Research Programme (EMRP) joint research project “Metrology for long distance surveying” the Finnish Geospatial Research Institute (FGI) is advancing the work for new measurement methods, uniform scale and improved metrological traceability. The FGI measured its Nummela Standard Baseline using the Väisälä Interference Comparator in 2013. The measurement continues the time series of nearly 70 years, during which the variation of the 864 123 mm total length has remained smaller than 0.7 mm. The result is traceable to the SI unit metre, and the expanded uncertainty is 0.2 mm. The new results provide comparison data for validation of novel surveying instruments within EMRP, and the scale from Nummela also has been transferred to a network of pillars at Metsähovi fundamental station and for comparisons to other European geodetic baselines. A metrologically optimum processing strategy for short GPS baselines has been studied. Different antenna calibrations, n...
22nd European VLBI for Geodesy and Astrometry (EVGA) Working Meeting, 2015
An experimental scanning of the Metsähovi radio telescope dish was carried out in August 2014. We... more An experimental scanning of the Metsähovi radio telescope dish was carried out in August 2014. We investigated a possibility to detect and estimate the elevation angle dependent deformations of the dish using terrestrial laser scanner. In this presentation we describe the practical organization of the experiment, instrumentation, measurements and quality of the data. We also describe the functional and stochastic model and algorithms which were used in data processing, paraboloid fitting, and the analysis of the solutions. The experiment shows that the terrestrial laser scanner is suitable for the focal length estimation. The analysis of the results reveals also possible deformations of the quadrapod structure. For investigating the surface of the dish we would like to repeat the measurements with more high accuracy
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Papers by Ulla Kallio
The experiment shows that the terrestrial laser scanner is suitable for the focal length estimation. The analysis of the results reveals also possible deformations of the quadrapod structure. For investigating the surface of the dish we would like to repeat the measurements with more high accuracy