Abstract During the 1950s–1970s, there were three geodesy professors in Sweden. Before and after that period the only such position was at KTH in Stockholm. One in the triple proposed the creation of the Nordic Geodetic Commission, which was realized in 1953 and still exists in much the same form as originally proposed.
{"title":"The three Swedish kings of geodesy – Speech at the NKG General Assembly dinner in 2022","authors":"L. Sjöberg","doi":"10.1515/jogs-2022-0152","DOIUrl":"https://doi.org/10.1515/jogs-2022-0152","url":null,"abstract":"Abstract During the 1950s–1970s, there were three geodesy professors in Sweden. Before and after that period the only such position was at KTH in Stockholm. One in the triple proposed the creation of the Nordic Geodetic Commission, which was realized in 1953 and still exists in much the same form as originally proposed.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"4 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80024695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The beginning of radars goes back to the 1930s where its main boost was related to the second world war. Nowadays, the techniques associated with radars are focused around a vast variety of civil, geodetic, and military applications. The development of the synthetic aperture principle, in the 1950s and 1960s, gave birth to a lot of new applications, and together with the technological progress of the last decades, the technique of interferometry with synthetic aperture radar (SAR) data became one of the most powerful ones for sensing remotely, with high quality and a vast spatial coverage. We used Sentinel-1 data and the differential interferometry SAR (DinSAR) technique to map and measure the surface deformation related to the 2015 Mw 8.3 Illapel earthquake (Chile). We also validated the results, by analysing the temporal variation of coordinates acquired from global navigation satellite system observations and projecting them in the geometry of the SAR system. Using this application we prove the DinSAR technique to be useful and powerful for the observation and analysis of surface deformation caused by the release of stress during the Mw 8.3 Illapel earthquake. It proved to be an efficient tool to detect and map the surface deformation with high spatial resolution in an approximate area of 20,000 km2.
{"title":"DinSAR coseismic deformation measurements of the Mw 8.3 Illapel earthquake (Chile)","authors":"Agustín Calvet, S. Balbarani, M. Gende","doi":"10.1515/jogs-2022-0154","DOIUrl":"https://doi.org/10.1515/jogs-2022-0154","url":null,"abstract":"Abstract The beginning of radars goes back to the 1930s where its main boost was related to the second world war. Nowadays, the techniques associated with radars are focused around a vast variety of civil, geodetic, and military applications. The development of the synthetic aperture principle, in the 1950s and 1960s, gave birth to a lot of new applications, and together with the technological progress of the last decades, the technique of interferometry with synthetic aperture radar (SAR) data became one of the most powerful ones for sensing remotely, with high quality and a vast spatial coverage. We used Sentinel-1 data and the differential interferometry SAR (DinSAR) technique to map and measure the surface deformation related to the 2015 Mw 8.3 Illapel earthquake (Chile). We also validated the results, by analysing the temporal variation of coordinates acquired from global navigation satellite system observations and projecting them in the geometry of the SAR system. Using this application we prove the DinSAR technique to be useful and powerful for the observation and analysis of surface deformation caused by the release of stress during the Mw 8.3 Illapel earthquake. It proved to be an efficient tool to detect and map the surface deformation with high spatial resolution in an approximate area of 20,000 km2.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"8 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86145335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hamed Karimi, S. Iran-Pour, A. Amiri-Simkooei, M. Babadi
Abstract Gravity recovery and climate experiment (GRACE) and GRACE Follow-On (GRACE-FO) are Earth’s gravity satellite missions with hydrological monitoring applications. However, caused by measuring instrumental problems, there are several temporal missing values in the dataset of the two missions where a long gap between the mission dataset also exists. Recent studies utilized different gap-filling methodologies to fill those data gaps. In this article, we employ a variety of singular spectrum analysis (SSA) algorithms as well as the least squares-harmonic estimation (LS-HE) approach for the data gap-filling. These methods are implemented on six hydrological basins, where the performance of the algorithms is validated for different artificial gap scenarios. Our results indicate that each hydrological basin has its special behaviour. LS-HE outperforms the other algorithms in half of the basins, whereas in the other half, SSA provides a better performance. This highlights the importance of different factors affecting the deterministic signals and stochastic characteristics of climatological time series. To fill the missing values of such time series, it is therefore required to investigate the time series behaviour on their time-invariant and time-varying characteristics before processing the series.
{"title":"A gap-filling algorithm selection strategy for GRACE and GRACE Follow-On time series based on hydrological signal characteristics of the individual river basins","authors":"Hamed Karimi, S. Iran-Pour, A. Amiri-Simkooei, M. Babadi","doi":"10.1515/jogs-2022-0129","DOIUrl":"https://doi.org/10.1515/jogs-2022-0129","url":null,"abstract":"Abstract Gravity recovery and climate experiment (GRACE) and GRACE Follow-On (GRACE-FO) are Earth’s gravity satellite missions with hydrological monitoring applications. However, caused by measuring instrumental problems, there are several temporal missing values in the dataset of the two missions where a long gap between the mission dataset also exists. Recent studies utilized different gap-filling methodologies to fill those data gaps. In this article, we employ a variety of singular spectrum analysis (SSA) algorithms as well as the least squares-harmonic estimation (LS-HE) approach for the data gap-filling. These methods are implemented on six hydrological basins, where the performance of the algorithms is validated for different artificial gap scenarios. Our results indicate that each hydrological basin has its special behaviour. LS-HE outperforms the other algorithms in half of the basins, whereas in the other half, SSA provides a better performance. This highlights the importance of different factors affecting the deterministic signals and stochastic characteristics of climatological time series. To fill the missing values of such time series, it is therefore required to investigate the time series behaviour on their time-invariant and time-varying characteristics before processing the series.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"36 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78161490","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. M. Wang, M. Véronneau, Jianliang Huang, K. Ahlgren, J. Krcmaric, Xiaopeng Li, D. Avalos-Naranjo
Abstract The geoid-quasigeoid separation (GQS) traditionally uses the Bouguer anomalies to approximate the difference between the mean gravity and normal gravity along the plumb line. This approximation is adequate in flat and low elevation areas, but not in high and rugged mountains. To increase the accuracy, higher order terms of the corrections (potential and gravity gradient) to the approximation were computed in Colorado where the 1 cm geoid computation experiment was conducted. Over an area of 730 km by 560 km where the elevation ranges between 932 and 4,385 m, the potential correction (Pot. Corr.) reaches −0.190 m and its root mean square (RMS) is 0.019 m. The gravity gradient correction is small but has high variation: the RMS of the correction is merely 0.003 m but varies from −0.025 to 0.020 m. In addition, the difference between the Bouguer gravity anomaly and gravity disturbance causes about a 0.01 m bias and a maximum correction of 0.02 m. The total corrections range from −0.135 to 0.180 m, with an RMS value of 0.019 m for the region. The magnitude of the corrections is large enough and is not negligible considering today’s cm-geoid requirement. After the test in Colorado, the complete GQS term is computed in 1′ × 1′ grids for the experimental geoid 2020 (xGEOID20), which covers a region bordered by latitude 0–85° north, longitude 180–350° east. Over the land areas, the RMS of the GQS is 0.119 m and the maximum reaches 1.3 m. The RMS of the GQS increases with respect to the height until 4,000 m, then decreases unexpectedly. At the highest peaks (5,500–6,000 m) of Denali and Mount Logan, the RMS of the GQS ranges between 0.08 and 0.189 m. The small GQS at these high peaks are caused by steep slopes around the peaks that produce large Pot. Corr. caused by the topography. In addition, the higher order correction terms reach half of a meter in those peaks.
{"title":"Accurate computation of geoid-quasigeoid separation in mountainous region – A case study in Colorado with full extension to the experimental geoid region","authors":"Y. M. Wang, M. Véronneau, Jianliang Huang, K. Ahlgren, J. Krcmaric, Xiaopeng Li, D. Avalos-Naranjo","doi":"10.1515/jogs-2022-0128","DOIUrl":"https://doi.org/10.1515/jogs-2022-0128","url":null,"abstract":"Abstract The geoid-quasigeoid separation (GQS) traditionally uses the Bouguer anomalies to approximate the difference between the mean gravity and normal gravity along the plumb line. This approximation is adequate in flat and low elevation areas, but not in high and rugged mountains. To increase the accuracy, higher order terms of the corrections (potential and gravity gradient) to the approximation were computed in Colorado where the 1 cm geoid computation experiment was conducted. Over an area of 730 km by 560 km where the elevation ranges between 932 and 4,385 m, the potential correction (Pot. Corr.) reaches −0.190 m and its root mean square (RMS) is 0.019 m. The gravity gradient correction is small but has high variation: the RMS of the correction is merely 0.003 m but varies from −0.025 to 0.020 m. In addition, the difference between the Bouguer gravity anomaly and gravity disturbance causes about a 0.01 m bias and a maximum correction of 0.02 m. The total corrections range from −0.135 to 0.180 m, with an RMS value of 0.019 m for the region. The magnitude of the corrections is large enough and is not negligible considering today’s cm-geoid requirement. After the test in Colorado, the complete GQS term is computed in 1′ × 1′ grids for the experimental geoid 2020 (xGEOID20), which covers a region bordered by latitude 0–85° north, longitude 180–350° east. Over the land areas, the RMS of the GQS is 0.119 m and the maximum reaches 1.3 m. The RMS of the GQS increases with respect to the height until 4,000 m, then decreases unexpectedly. At the highest peaks (5,500–6,000 m) of Denali and Mount Logan, the RMS of the GQS ranges between 0.08 and 0.189 m. The small GQS at these high peaks are caused by steep slopes around the peaks that produce large Pot. Corr. caused by the topography. In addition, the higher order correction terms reach half of a meter in those peaks.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"138 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75694895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. L. Carrión, Sílvio R. Correia de Freitas, R. Barzaghi
Abstract In this work, the determination of the discrepancy between the Ecuadorian Vertical Datum (EVD) and the International Height Reference System (IHRS) is presented. The vertical offset was estimated at the EVD based on the fixed geodetic boundary value problem approach. The focus of the experiment was the determination of the anomalous potential in the EVD, which in turn enable determination of the respective geopotential value. Taking a geopotential space-based approach, two estimates of the EVD offset with respect to the IHRS were obtained that amount to −1.51 and −1.61 m2/s2.
{"title":"On the connection of the Ecuadorian Vertical Datum to the IHRS","authors":"J. L. Carrión, Sílvio R. Correia de Freitas, R. Barzaghi","doi":"10.1515/jogs-2022-0151","DOIUrl":"https://doi.org/10.1515/jogs-2022-0151","url":null,"abstract":"Abstract In this work, the determination of the discrepancy between the Ecuadorian Vertical Datum (EVD) and the International Height Reference System (IHRS) is presented. The vertical offset was estimated at the EVD based on the fixed geodetic boundary value problem approach. The focus of the experiment was the determination of the anomalous potential in the EVD, which in turn enable determination of the respective geopotential value. Taking a geopotential space-based approach, two estimates of the EVD offset with respect to the IHRS were obtained that amount to −1.51 and −1.61 m2/s2.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"8 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81189855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Cunderlík, R. Tenzer, M. Macák, P. Zahorec, J. Papčo, Albertini Nsiah Ababio
Abstract New gravity and precise levelling measurements have been performed throughout the Hong Kong territories to modernize a vertical geodetic datum that is currently realized by heights of levelling benchmarks defined in the Hong Kong Principal Datum (HKPD). Modernization of the HKPD involved delivering various products, including new detailed geoid and quasigeoid models and newly determined orthometric and normal heights of levelling benchmarks. In this study, we present the result of gravimetric quasigeoid modelling. The method used to compute a detailed gravimetric quasigeoid model is based on the finite-element method to solve the geodetic boundary-value problem with oblique derivative boundary conditions considered directly at computational nodes on the discretized Earth’s topography. The result of a gravimetric quasigeoid modelling shows a good agreement with a geometric quasigeoid model at the Global Navigation Satellite System (GNSS)-levelling benchmarks. The standard deviation of differences between the gravimetric and geometric quasigeoid heights of ±3.3 cm is compatible with the expected accuracy of gravity, levelling, and GNSS measurements.
{"title":"A detailed quasigeoid model of the Hong Kong territories computed by applying a finite-element method of solving the oblique derivative boundary-value problem","authors":"R. Cunderlík, R. Tenzer, M. Macák, P. Zahorec, J. Papčo, Albertini Nsiah Ababio","doi":"10.1515/jogs-2022-0153","DOIUrl":"https://doi.org/10.1515/jogs-2022-0153","url":null,"abstract":"Abstract New gravity and precise levelling measurements have been performed throughout the Hong Kong territories to modernize a vertical geodetic datum that is currently realized by heights of levelling benchmarks defined in the Hong Kong Principal Datum (HKPD). Modernization of the HKPD involved delivering various products, including new detailed geoid and quasigeoid models and newly determined orthometric and normal heights of levelling benchmarks. In this study, we present the result of gravimetric quasigeoid modelling. The method used to compute a detailed gravimetric quasigeoid model is based on the finite-element method to solve the geodetic boundary-value problem with oblique derivative boundary conditions considered directly at computational nodes on the discretized Earth’s topography. The result of a gravimetric quasigeoid modelling shows a good agreement with a geometric quasigeoid model at the Global Navigation Satellite System (GNSS)-levelling benchmarks. The standard deviation of differences between the gravimetric and geometric quasigeoid heights of ±3.3 cm is compatible with the expected accuracy of gravity, levelling, and GNSS measurements.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"134 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86344860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anna Przewięźlikowska, Wioletta Ślusarczyk, Klaudia Wójcik, K. Maciuk
Abstract To prepare the mobile application for the ongoing update of the control network, it is necessary to define detailed procedures for dealing with the points database. These procedures concern the determination of the methodology of making an inventory of the existing database and then the determination of the rules for updating the control network using the developed application. This part describes a practical verification of Metrica for collecting control points data and showing specific cases in the collection and sharing of such data. There were created field inspections using nine different criteria on the set of selected points. Analysis shows that a large part of the points need to be reviewed once again, and its description needs to be updated.
{"title":"Metrica – An application for collecting and navigating to geodetic control network points. Part II: Practical verification","authors":"Anna Przewięźlikowska, Wioletta Ślusarczyk, Klaudia Wójcik, K. Maciuk","doi":"10.1515/jogs-2022-0147","DOIUrl":"https://doi.org/10.1515/jogs-2022-0147","url":null,"abstract":"Abstract To prepare the mobile application for the ongoing update of the control network, it is necessary to define detailed procedures for dealing with the points database. These procedures concern the determination of the methodology of making an inventory of the existing database and then the determination of the rules for updating the control network using the developed application. This part describes a practical verification of Metrica for collecting control points data and showing specific cases in the collection and sharing of such data. There were created field inspections using nine different criteria on the set of selected points. Analysis shows that a large part of the points need to be reviewed once again, and its description needs to be updated.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"191 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75821429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The book “Physical Geodesy” by Martin Vermeer is written in a proper pedagogic way with a simple and complete text, good examples, conceptual questions and excellent exercises at the end of each chapter. This book is a suitable reference for educational purposes in Physical Geodesy from the bachelor to higher levels of education.
{"title":"Physical Geodesy by Martin Vermeer published by Aalto University Press 2020","authors":"M. Eshagh","doi":"10.1515/jogs-2022-0150","DOIUrl":"https://doi.org/10.1515/jogs-2022-0150","url":null,"abstract":"Abstract The book “Physical Geodesy” by Martin Vermeer is written in a proper pedagogic way with a simple and complete text, good examples, conceptual questions and excellent exercises at the end of each chapter. This book is a suitable reference for educational purposes in Physical Geodesy from the bachelor to higher levels of education.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"65 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85398685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The International Height Reference System (IHRS) was defined by the International Association of Geodesy in 2015. Since then, the international geodetic community has been working on the specification and establishment of its realisation, the International Height Reference Frame (IHRF). This frame will primarily be realised by geopotential numbers (or physical heights) in a sparse global reference network. In Sweden, only one such global station is planned. Regional and national realisations (or densifications) computed in accordance with the IHRS definition are needed to enable the best possible unification of height datums. The main purpose of this article is to make a case study for Sweden regarding the national realisation of IHRS and to investigate in what way preliminary IHRF differs from the current Swedish levelling-based realisation of the European Vertical Reference System, RH 2000. The two different quasigeoid models that we consider best over Sweden at the present time are used to compute the preliminary IHRS realisations in the study. The realisations are compared to each other and to RH 2000. It is shown that a very significant part of the difference to RH 2000 is due to the different postglacial land uplift epochs, permanent tide concepts, and zero levels. The standard deviation for the difference between one of the preliminary national IHRS realisations and RH 2000 is reduced from 75.5 to 19.2 mm after correction of the postglacial land uplift and permanent tide effects. The corresponding mean differences are –208.5 and –454.7 mm, respectively. The magnitude of the mean difference thus increases when the corrections in question are applied.
{"title":"A first step towards a national realisation of the international height reference system in Sweden with a comparison to RH 2000","authors":"Anders Alfredsson, Jonas Ågren","doi":"10.1515/jogs-2022-0156","DOIUrl":"https://doi.org/10.1515/jogs-2022-0156","url":null,"abstract":"Abstract The International Height Reference System (IHRS) was defined by the International Association of Geodesy in 2015. Since then, the international geodetic community has been working on the specification and establishment of its realisation, the International Height Reference Frame (IHRF). This frame will primarily be realised by geopotential numbers (or physical heights) in a sparse global reference network. In Sweden, only one such global station is planned. Regional and national realisations (or densifications) computed in accordance with the IHRS definition are needed to enable the best possible unification of height datums. The main purpose of this article is to make a case study for Sweden regarding the national realisation of IHRS and to investigate in what way preliminary IHRF differs from the current Swedish levelling-based realisation of the European Vertical Reference System, RH 2000. The two different quasigeoid models that we consider best over Sweden at the present time are used to compute the preliminary IHRS realisations in the study. The realisations are compared to each other and to RH 2000. It is shown that a very significant part of the difference to RH 2000 is due to the different postglacial land uplift epochs, permanent tide concepts, and zero levels. The standard deviation for the difference between one of the preliminary national IHRS realisations and RH 2000 is reduced from 75.5 to 19.2 mm after correction of the postglacial land uplift and permanent tide effects. The corresponding mean differences are –208.5 and –454.7 mm, respectively. The magnitude of the mean difference thus increases when the corrections in question are applied.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"100 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135595136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Despite being in use for more than 150 years, the error accumulation in precise levelling has not yet been completely clarified. It is believed that the error accumulation in this method is proportional to the square root of the levelling length. The first goal of this article is to demonstrate that this belief is not always scientifically proven. The second aim is to show that it is likely that a better adjustment decision will be missed if inverse distance weighting with a power parameter equal to one is automatically applied. Using linear regression analysis the measuring data of the Second Levelling of Finland is analysed. An inadequacy of the relationship between the absolute values of the differences between both measurements of the elevations in the levelling lines and their length is shown, which is due to heteroscedasticity. In order to obtain a homoscedastic model, the other two models are constructed. Based on the regression analysis results, the network is adjusted using three types of weights. The adjustment with traditional weights has produced significantly greater mean errors of the nodal benchmarks than both variants based on weights, which are functions of the absolute values of the line elevations.
{"title":"Two adjustments of the second levelling of Finland by using nonconventional weights","authors":"Vasil Cvetkov","doi":"10.1515/jogs-2022-0148","DOIUrl":"https://doi.org/10.1515/jogs-2022-0148","url":null,"abstract":"Abstract Despite being in use for more than 150 years, the error accumulation in precise levelling has not yet been completely clarified. It is believed that the error accumulation in this method is proportional to the square root of the levelling length. The first goal of this article is to demonstrate that this belief is not always scientifically proven. The second aim is to show that it is likely that a better adjustment decision will be missed if inverse distance weighting with a power parameter equal to one is automatically applied. Using linear regression analysis the measuring data of the Second Levelling of Finland is analysed. An inadequacy of the relationship between the absolute values of the differences between both measurements of the elevations in the levelling lines and their length is shown, which is due to heteroscedasticity. In order to obtain a homoscedastic model, the other two models are constructed. Based on the regression analysis results, the network is adjusted using three types of weights. The adjustment with traditional weights has produced significantly greater mean errors of the nodal benchmarks than both variants based on weights, which are functions of the absolute values of the line elevations.","PeriodicalId":44569,"journal":{"name":"Journal of Geodetic Science","volume":"13 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87079429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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