Conversión entre coordenadas geodésicas y coordenadas locales

En este artículo se aborda la conversión entre coordenadas geodésicas y coordenadas expresadas en un sistema cartesiano local, tanto en sentido directo como recíproco. La solución planteada está basada exclusivamente en conversiones de coordenadas, rotaciones y traslaciones, por lo que mantiene intacta la geometría relativa de los puntos.García-Asenjo Villamayor, L. (2017). Conversión entre coordenadas geodésicas y coordenadas locales. http://hdl.handle.net/10251/84060DE

Valoración de la calidad de imágenes panorámicas esféricas

[EN] In recent years, the production of panoramic images has been boosted by the increasing use of digital photographiccameras and mobile phones. However, for highly demanding applications such as long-range deformation monitoring, theaccuracy and quality control of panoramic images and processes used to obtain accurate 3D models should be properlyassessed. Therefore, prior to being applied in real projects, the quality of the spherical panoramic images generated bythree widely used computer programs (Agisoft Metashape, GigaPan Stitch and PTGui) is evaluated using the same imagesof a photogrammetric laboratory full of control points and an outdoor environment by shooting from several stations. Inaddition to the assessment of the geometrical accuracy, the study also includes important aspects for practical efficiencysuch as workflow, speed of processing, user-friendliness, or exporting products and formats available. The results of thecomparisons show that Agisoft Metashape meets the required geometric specifications with higher quality and has clearadvantages in performance if compared to the other two tested programs.[ES] En los últimos años, la producción de imágenes panorámicas se ha visto impulsada por el uso cada vez mayor de cámaras fotográficas digitales y teléfonos móviles. Sin embargo, deben evaluarse adecuadamente en aplicaciones altamente exigentes como la monitorización de deformaciones a grandes distancias, la precisión y el control de calidad de las imágenes panorámicas y los procesos utilizados para obtener modelos 3D precisos. Por consiguiente, antes de ser aplicadas en proyectos reales, se evalúa la calidad de las imágenes panorámicas esféricas generadas por tres programas informáticos ampliamente utilizados (Agisoft Metashape, GigaPan Stitch y PTGui) utilizando las mismas imágenes de un laboratorio fotogramétrico lleno de puntos de apoyo y del exterior desde varias estaciones. Además de la evaluación de la precisión geométrica, el estudio también incluye aspectos importantes para la eficiencia práctica como es el flujo de trabajo, la velocidad de procesamiento, la facilidad de uso o la exportación de productos y los formatos disponibles. Los resultados de las comparaciones muestran que Agisoft Metashape cumple con las especificaciones geométricas requeridas con mayor calidad y tiene claras ventajas de rendimiento si se compara con los otros dos programas testeados.Javadi, P.; Lerma, J.; García-Asenjo, L.; Garrigues, P. (2021). Quality assessment of spherical panoramic images. En Proceedings 3rd Congress in Geomatics Engineering. Editorial Universitat Politècnica de València. 7-14. https://doi.org/10.4995/CiGeo2021.2021.12728OCS71

Optimal combination and reference functions of signal-to-noise measurements for GNSS multipath detection

[EN] Multipath is the most limiting factor in many GNSS positioning applications, where it inevitably degrades the attainable precision. Among the different proposals to identify observations affected by multipath, Strode and Groves have recently proposed a method based on the comparison of GPS signal-to-noise (SNR) actual measurements with suitable reference functions previously computed in a low-multipath environment. We have found significant issues with its application to our particular GNSS experiments, however. In particular, we discuss whether the reference functions that are needed to be computed for low-multipath environments after tedious and time consuming field campaigns can be used for a future occasion, or not, as well as the possibility of applying the method to other GNSS global constellations (Galileo and GLONASS). Additionally, we elaborate on an alternative idea consisting in the use of the best combination of SNR measurements for the different signals in the different constellations in order to obtain a multipath estimator that is unbiased, universal and performs better than the use of reference functions.Pánik, P.; García-Asenjo Villamayor, L.; Baselga Moreno, S. (2019). Optimal combination and reference functions of signal-to-noise measurements for GNSS multipath detection. Measurement Science and Technology. 30(4):1-13. https://doi.org/10.1088/1361-6501/ab05aeS11330

Long and Lose-Range Terrestrial Photogrammetry for Rocky Landscape Deformation Monitoring

[EN] The paper describes the processing and validation of a series of terrestrial photogrammetric surveys carried out from 2017 to 2020 for monitoring the stability of a cliff in Cortes de Pallás (Spain). The complexity of the target area, which has a strong orography, a water reservoir, and many obstacles such as electrical power lines or vegetation, makes difficult the use of any measurement technique. After considering solutions such as long-range laser scanning or close-range mobile mapping, which were unsatisfactorily tested and therefore rejected for future campaigns, the use of combined short and long terrestrial photogrammetry proved an efficient method for quick and massive monitoring of the entire cliff with an overall accuracy of several centimetres. All the steps undertaken for the centimetre level accuracy deliverables, which include camera calibration, bundle-adjustment, dense point cloud generation, 3D modelling, and validation of the 3D models by using external geodetic information, will be presented. For the sake of conciseness, only results for the last two campaigns (5th and 6th), as well as the comparison between the last (6th) and the first (1st) campaigns, will be discussed. In addition, photogrammetric results will be validated by analyzing the metrics on four target-based micro-geodetic check points, located on key critical areas of the cliff selected by civil and geotechnical engineers from the Department of Roads and Infrastructures.Cabrelles, M.; Lerma, J.; García-Asenjo, L.; Garrigues, P.; Martínez, L. (2023). Long and Lose-Range Terrestrial Photogrammetry for Rocky Landscape Deformation Monitoring. En 5th Joint International Symposium on Deformation Monitoring (JISDM 2022). Editorial Universitat Politècnica de València. 485-491. https://doi.org/10.4995/JISDM2022.2022.1393348549

Deformation Monitoring of the Submillimetric UPV Calibration Baseline

[EN] A 330 m calibration baseline was established at the Universitat Politecnica de Valencia (UPV) in 2007. Absolute scale was subsequently transferred in 2012 from the Nummela Standard Baseline in Finland and distances between pillars were determined with uncertainties ranging from 0.1 mm to 0.3 mm. In order to assess the longterm stability of the baseline three field campaigns were carried out from 2013 to 2015 in a co-operative effort with the Universidad Complutense de Madrid (UCM), which-provided the only Mekometer ME5000 distance meter available in Spain. Since the application of the ISO17123-4 full procedure did not suffice to come to a definite conclusion about possible displacements of the pillars, we opted for the traditional geodetic network approach. This approach had to be adapted to the case at hand in order to deal with problems such as the geometric weakness inherent to calibration baselines and scale uncertainty derived from both the use of different instruments and the high correlation between the meteorological correction and scale determination. Additionally, the so- called the maximum number of stable points method was also tested. In this contribution it is described the process followed to assess the stability of the UPV submillimetric calibration baseline during the period of time from 2012 to 2015.Spanish Ministry of Science and Innovation, (Grant/Award Number: 'AYA2011-23232').García-Asenjo Villamayor, L.; Baselga Moreno, S.; Garrigues Talens, P. (2017). Deformation Monitoring of the Submillimetric UPV Calibration Baseline. Journal of Applied Geodesy. 11(2):107-114. https://doi.org/10.1515/jag-2016-0018S10711411

GBDM+: an improved methodology for a GNSS-based distance meter

[EN] The determination of distances consistent with the definition of the base unit of length in the International System of Units (SI), the SI meter, with uncertainties of less than 1 ppm up to 5 km in the open air is a current challenge that is being increasingly required for different applications, including the determination of local ties, calibration baselines, and high precision geodetic metrology in singular scientific and engineering projects. The required knowledge of the index of refraction of the propagating medium at the same level of 1 ppm is a hard limit to the use of precise electronic distance meters (EDMs), which has motivated the recent development of new two-color, refractivity compensated, EDM prototypes. As an alternative, the use of global navigation satellite systems (GNSS) could benefit from their high scale stability although the lack of appropriate estimation of the uncertainties in their sources of error and their unknown propagation into the final result during the data processing has prevented a rigorous uncertainty analysis and, therefore, the use of GNSS for absolute distance determination. Stemming from our initial methodology for a GNSS-based distance meter (GBDM) that was restricted to relatively horizontal baselines and distances up to 1 km only, we have improved the method so that its application range is extended to baselines of up to 5 km with a possibly significant height difference so that it provides the final baseline distance with the corresponding uncertainty derived from the uncertainties in the different error sources rigorously propagated through the equations by which the distance is finally determined. This improved methodology, named as GBDM+, constitutes a significant step forward in the application of GNSS to open air length metrology.The work leading to this paper was performed within the 18SIB01 GeoMetre project of the European Metrology Programme for Innovation and Research (EMPIR). This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme, funder ID: 10.13039/100014132. Raquel Lujan acknowledges the funding from the Programa de Ayudas de Investigacion y Desarrollo (PAID-01-20) de la Universitat Politecnica de Valencia.Baselga Moreno, S.; García-Asenjo Villamayor, L.; Garrigues Talens, P.; Luján, R. (2022). GBDM+: an improved methodology for a GNSS-based distance meter. Measurement Science and Technology. 33(8):1-16. https://doi.org/10.1088/1361-6501/ac6f4511633

Development of a Submillimetric GNSS-Based Distance Meter for Length Metrology

[EN] Absolute distance determination in the open air with an uncertainty of a few tenths of a millimetre is increasingly required in many applications that involve high precision geodetic metrology. No matter the technique used to measure, the resulting distances must be proven consistent with the unit of length (SI-metre) as realized in the outdoor facilities traditionally used in length metrology, which are also known as calibration baselines of reference. The current calibration baselines of reference have distances in the range of 10 to 1000 m, but at present there is no solution on the market to provide distances with submillimetric precision in that range. Consequently, new techniques such as multi-wave interferometry, two-wave laser telemeters or laser trackers are being developed. A possible alternative to those sophisticated and expensive techniques is the use of widely used Global Navigation Satellite Systems (GNSS) in order to provide a GNSS-Based Distance Meter (GBDM). The use of a GBDM as a potential technique for length metrology has been thoroughly analysed in several European research projects by using the state-of-the-art geodetic software, such as Bernese 5.2, but no definite conclusions have been drawn and some metrological questions are considered still open. In this paper, we describe a dedicated approach to build up a submillimetric GBDM able to be applied in the current calibration baselines of reference, as well as possible methods to cope with the multipath error of the GNSS signals which is the major limitation for the practical uptaking of the technique in metrology. The accuracy of the proposed approach has been tested following the length metrology standards in four experiments carried out in the Universitat Politecnica de Valencia (UPV). The results demonstrate that the proposed GBDM can provide an accuracy of a few tenths of a millimetre in the current calibration baselines of referenceThis work was partly performed within the 18SIB01 GeoMetre project of the European Metrology Programme for Innovation and Research (EMPIR). This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. This research was also partly funded by the Spanish Ministry of Education, Culture and Sports (PRX17/00371).García-Asenjo Villamayor, L.; Baselga Moreno, S.; Atkins, C.; Garrigues Talens, P. (2021). Development of a Submillimetric GNSS-Based Distance Meter for Length Metrology. Sensors. 21(4):1-21. https://doi.org/10.3390/s2104114512121

Practical formulas for the refraction coefficient

Knowledge of the actual refraction coefficient is essential in leveling surveys and precise electromagnetic distance measurement reduction. The most common method followed by the surveyor for its determination is based on the use of simultaneous reciprocal zenith observations. The commonly used formula is only an approximation valid for approximately horizontal sightings, whereas the exact geometric solution turns out to be very complicated so that an iterative computation procedure is suggested instead. In the present paper, the goal is to derive a compact formula from the complete solution that is easy to implement and retains the necessary accuracy for horizontal and slanted sightings. In addition, the paper will also focus on the common situation for the surveyor where isolated observations have to be done and no partially compensating procedures—e.g., leap-frog or middle point—are possible. If temperature vertical profiles are unknown then the refraction coefficient cannot be reliably determined. Some surveyors may customarily use then an average value, e.g., k 5 0:13, perhaps being unaware of the risks involved in such simplistic assumption. In the present paper, it is also a goal to present a useful and simple formula for approximately estimating the refraction coefficient in terms of easily accessible parameters to correct the bulk of the refraction effect in single observations, always bearing in mind that determination of the refraction coefficient by means of a model may turn out to be somewhat inaccurate, but still better than the blind use of a universal k.The authors are grateful to the editor and the anonymous reviewers for their valuable suggestions, corrections, and comments that helped improve the original manuscript. This research is funded by the Spanish Ministry of Science and Innovation (Grant No. AYA2011-23232).Baselga Moreno, S.; García-Asenjo Villamayor, L.; Garrigues Talens, P. (2014). Practical formulas for the refraction coefficient. Journal of Surveying Engineering. 140(2):1-5. https://doi.org/10.1061/(ASCE)SU.1943-5428.0000124S15140

Evaluation of Long-Range Mobile Mapping System (MMS) and Close-Range Photogrammetry for Deformation Monitoring. A Case Study of Cortes de Pallás in Valencia (Spain)

none8openDi Stefano, Francesco; Cabrelles, Miriam; García-Asenjo, Luis; Lerma, José Luis; Malinverni, Eva Savina; Baselga, Sergio; Garrigues, Pascual; Pierdicca, RobertoDi Stefano, Francesco; Cabrelles, Miriam; García-Asenjo, Luis; Lerma, José Luis; Malinverni, Eva Savina; Baselga, Sergio; Garrigues, Pascual; Pierdicca, Robert