ILRS Reference Point Determination Using Close Range Photogrammetry

Lösler, Michael; Eschelbach, Cornelia; Klügel, Thomas; Riepl, Stefan

doi:10.3390/app11062785

Cited by 8 publications

(10 citation statements)

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“…At the Geodetic Observatory Wettzell, the new approach has been evaluated using close-range photogrammetry for the first time (Lösler et al 2021;2022a). The reference point of the two-colour laser telescope, the Satellite Observing System Wettzell, was derived several times in a local frame using various configurations.…”

Section: Reference Point Monitoringmentioning

confidence: 99%

“…If the fully populated dispersion matrix is reduced to a diagonal variance matrix or a uniformed scaled identity matrix-as usually used in industrial applications-the obtained uncertainties are up to three-time overestimated with respect to the fully populated dispersion matrix. A detailed description of the measurement campaign and the data analysis can be found in (Lösler et al 2021;Eschelbach et al 2022).…”

Section: Reference Point Monitoringmentioning

confidence: 99%

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The European GeoMetre project: developing enhanced large-scale dimensional metrology for geodesy

et al. 2023

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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 use our novel instruments for a reduced uncertainty of the scale in the surveillance networks solutions for local tie measurements at space-geodetic co-location stations. We also investigate novel approaches like close-range photogrammetry to reference point determination of space-geodetic telescopes. Finally, we also investigate the inclusion of the local gravity field to consider the deviations of the vertical in the data analysis and to reduce the uncertainty of coordinate transformations in this complex problem.

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Section: Reference Point Monitoringmentioning

confidence: 99%

Section: Reference Point Monitoringmentioning

confidence: 99%

The European GeoMetre project: developing enhanced large-scale dimensional metrology for geodesy

et al. 2023

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“…Initially, the model was derived for reference point determination at VLBI radio telescopes (Lösler 2008). However, the model is also valid for telescopes used for SLR as recently demonstrated by Lösler et al (2018Lösler et al ( , 2021 and Eschelbach and Lösler (2022). In contrast to geometrical approaches like the circle-fitting approach (Leinen et al 2007;Gong et al 2014), Eq.…”

Section: Slr/vlbi Reference Pointmentioning

confidence: 99%

Operator-software impact in local tie networks

et al. 2023

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The operator-software impact describes the differences between results introduced by different operators using identical software packages but applying different analysis strategies to the same data. This contribution studies the operator-software impact in the framework of local tie determination, and compares two different analysis approaches. Both approaches are used in present local tie determinations and mainly differ in the consideration of the vertical deflection within the network adjustment. However, no comparison study has yet been made so far. Selecting a suitable analysis approach is interpreted as a model selection problem, which is addressed by information criteria within this investigation. A suitable model is indicated by a sufficient goodness of fit and an adequate number of model parameters. Moreover, the stiffness of the networks is evaluated by means of principal component analysis. Based on the date of a measurement campaign performed at the Geodetic Observatory Wettzell in 2021, the impact of the analysis approach on local ties is investigated. For that purpose, an innovated procedure is introduced to obtain reference points of space geodetic techniques defining the local ties. Within the procedure, the reference points are defined independently of the used reference frame, and are based on geometrical conditions. Thus, the results depend only on the estimates of the performed network adjustment and, hence, the applied network analysis approach. The comparison of the horizontal coordinates of the determined reference points shows a high agreement. The differences are less than 0.2 mm. However, the vertical components differ by more than 1 mm, and exceed the coverage of the estimated standard deviations. The main reasons for these large discrepancies are a network tilting and a network bending, which is confirmed by a residual analysis.

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“…The reference points are then estimated in the reference frame of the local survey network using mathematical models (e.g. Harvey (1991), Sarti et al (2004), Dawson et al (2007), Lösler (2009), Kallio and Poutanen (2012), Lösler et al (2021)). GNSS observations refer to the ARP (Antenna Reference Point) at least theoretically with certain uncertainty when antenna calibration tables with Phase Center Offset and Phase Center Variation are used.…”

Section: Introductionmentioning

confidence: 99%

“…The reference point estimation gives the uncertainty of the monitoring part but not the uncertainty of the datum definition part of the local survey network. It has been proved that reference point coordinates can be determined within 0.01mm precision using close-range photogrammetry (Lösler et al 2021). Thus a small monitoring network, spanning a couple of meters, can be internally extremely accurate.…”

Section: Introductionmentioning

confidence: 99%

Datum Problem Handling in Local Tie Surveys at Wettzell and Metsähovi

Kallio

Klügel

Marila

et al. 2022

International Association of Geodesy Symposia

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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 ellipsoid. Horizontally the observed set of angles are oriented in arbitrary or approximately oriented directions.External information which is needed for solving the absolute orientation are datum points, providing the link to the global coordinate system, and correction terms for the vertical orientation (deflection of the vertical), which can be derived from combined terrestrial/GNSS observations, from a gravity based geoid model, or from astronomical observations.In this article, we present the solutions/options for the datum problem in the framework of the EMPIR GeoMetre project using the example of the ITRF core stations Metsähovi and Wettzell using transformation-free approaches. The inclusion of distant targets is promising, since in small networks even a millimeter change in the coordinates of a datum point can significantly affect a local tie vector. It is shown that at both stations the determination of the deflection of the vertical using different techniques yield the same results within the measurement error.

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ILRS Reference Point Determination Using Close Range Photogrammetry

Cited by 8 publications

References 50 publications

The European GeoMetre project: developing enhanced large-scale dimensional metrology for geodesy

The European GeoMetre project: developing enhanced large-scale dimensional metrology for geodesy

Operator-software impact in local tie networks

Datum Problem Handling in Local Tie Surveys at Wettzell and Metsähovi

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