scholarly journals Estimating Canadian vertical datum offsets using GNSS/levelling benchmark information and GOCE global geopotential models

2012 ◽  
Vol 2 (4) ◽  
pp. 257-269 ◽  
Author(s):  
T. Hayden ◽  
B. Amjadiparvar ◽  
E. Rangelova ◽  
M.G. Sideris
Keyword(s):  
High Resolution ◽  
Geoid Height ◽  
Omission Error ◽  
Control Network ◽  
Commission Error ◽  
Vertical Control ◽  
Geopotential Models ◽  
Vertical Datum ◽  
Local Vertical Datum ◽  
Omission Errors

AbstractThe performance of GOCE-based geopotential models is assessed for the estimation of offsets for three regional vertical datums in Canada with respect to a global equipotential surface using the GNSS benchmarks from the first-order vertical control network. Factors that affect the computed value of the local vertical datum offset include the GOCE commission and omission errors, measurement errors, the configuration of the network of GNSS/levelling benchmarks, and systematic levelling errors and distortions propagated through the vertical control network. Among these various factors, the effect of the GOCE omission error on the datum offsets is investigated by extending the models with the high resolution gravity field model EGM2008 and by means of Canada’s official high resolution geoid model CGG2010. The effect of the GOCE commission error in combination with errors from the GNSS/levelling data is also examined, in addition to the effect of systematic levelling errors. In Canada, the effect of the GOCE omission error is at the dm-level when computing local vertical datum offsets. The effect of including accuracy information for the GNSS/levelling data and the GOCE geoid heights can be up to 4 cm over the Canadian mainland and at the dm-level for island regions. Lastly, the spatial tilts found in the levelling network can be modelled with a 2-parameter bias corrector model, which reduces the RMS of the adjusted geoid height differences by 4 cm when compared to the RMS of adjusted geoid height differences computed without the use of a bias corrector model. Thus, when computing local vertical datum offsets in Canada, it is imperative to account for GOCE commission and omission errors, ellipsoidal and levelling height errors, as well as the systematic levelling errors of the vertical control network.

scholarly journals Intercontinental height datum connection with GOCE and GPS-levelling data

2012 ◽  
Vol 2 (4) ◽  
pp. 270-280 ◽  
Author(s):  
T. Gruber ◽  
C. Gerlach ◽  
R. Haagmans
Keyword(s):  
Gravity Field ◽  
Ocean Circulation ◽  
Omission Error ◽  
Commission Error ◽  
Optimal Point ◽  
Point Distribution ◽  
Gravity Field Model ◽  
Vertical Datum ◽  
Height Datum ◽  
The Mean

AbstractIn this study an attempt is made to establish height system datum connections based upon a gravity field and steady-state ocean circulation explorer (GOCE) gravity field model and a set of global positioning system (GPS) and levelling data. The procedure applied in principle is straightforward. First local geoid heights are obtained point wise from GPS and levelling data. Then the mean of these geoid heights is computed for regions nominally referring to the same height datum. Subsequently, these local mean geoid heights are compared with a mean global geoid from GOCE for the same region. This way one can identify an offset of the local to the global geoid per region. This procedure is applied to a number of regions distributed worldwide. Results show that the vertical datum offset estimates strongly depend on the nature of the omission error, i.e. the signal not represented in the GOCE model. For a smooth gravity field the commission error of GOCE, the quality of the GPS and levelling data and the averaging control the accuracy of the vertical datum offset estimates. In case the omission error does not cancel out in the mean value computation, because of a sub-optimal point distribution or a characteristic behaviour of the omitted part of the geoid signal, one needs to estimate a correction for the omission error from other sources. For areas with dense and high quality ground observations the EGM2008 global model is a good choice to estimate the omission error correction in theses cases. Relative intercontinental height datum offsets are estimated by applying this procedure between the United State of America (USA), Australia and Germany. These are compared to historical values provided in the literature and computed with the same procedure. The results obtained in this study agree on a level of 10 cm to the historical results. The changes mainly can be attributed to the new global geoid information from GOCE, rather than to the ellipsoidal heights or the levelled heights. These historical levelling data are still in use in many countries. This conclusion is supported by other results on the validation of the GOCE models.

Study on Key Technology in the Control Surveying of Jinan-Qingdao Highway’s South Line

2011 ◽  
Vol 90-93 ◽  
pp. 2853-2857
Author(s):  
De Bao Wang ◽  
Xue Ling Fang
Keyword(s):  
Coordinate System ◽  
High Precision ◽  
Survey Design ◽  
Control Network ◽  
Central Meridian ◽  
Key Technology ◽  
Primary Survey ◽  
Vertical Control ◽  
Vertical Datum ◽  
Selection Of

The south line of Jinan Qingdao highway (which is short of Ji-Qing south line) spans 281km, whose geomorphy is mainly composed by mountain lands and hills. Approximately, it runs from east to west and straddles several projection zones. Systemic conformance of its layout and measurement, high precision in company with multifunctional planes and vertical control nets make up this project’s key technological problems. The report tells of the selection of central meridian in different areas of Ji-Qing south line and the layout, observation, adjustment, height fitting and precision statistics of GPS control network; the layout, observation, adjustment and precision counting of vertical control nets; Meanwhile, it analyses and discusses that how to guarantee the systemic conformance of coordinate system and vertical datum, together with eliminating the division of points’ coordinates and elevation values’ steps when primary survey design are being made synchronously in two super highways or in different areas of the same expressway.

scholarly journals Estimation of Vertical Datum Parameters Using the GBVP Approach Based on the Combined Global Geopotential Models

2020 ◽  
Vol 12 (24) ◽  
pp. 4137
Author(s):  
Panpan Zhang ◽  
Lifeng Bao ◽  
Dongmei Guo ◽  
Lin Wu ◽  
Qianqian Li ◽  
...  
Keyword(s):  
Gravity Field ◽  
Ocean Circulation ◽  
Omission Error ◽  
Practical Implementation ◽  
Geopotential Model ◽  
Weighting Method ◽  
The North ◽  
Main Challenge ◽  
Vertical Datum ◽  
Local Vertical Datum

Unification of the global vertical datum has been a key problem to be solved for geodesy over a long period, and the main challenge for a unified vertical datum system is to determine the vertical offset between the local vertical datum and the global vertical datum. For this purpose, the geodetic boundary value problem (GBVP) approach based on the remove-compute-restore (RCR) technique is used to determine the vertical datum parameters in this paper. In the RCR technique, a global geopotential model (GGM) is required to remove and restore the long wavelengths of the gravity field. The satellite missions of the GRACE (Gravity Recovery and Climate Experiment) and GOCE (Gravity field and steady-state Ocean Circulation Exploration) offer high accuracy medium–long gravity filed information, but GRACE/GOCE-based GGMs are restricted to medium–long wavelengths because the maximum degree of their spherical harmonic representation is limited, which is known as an omission error. To compensate for the omission error of GRACE/GOCE-based GGM, a weighting method is used to determine the combined GGM by combining the high-resolution EGM2008 model (Earth Gravitational Model 2008) and GRACE/GOCE-based GGM to effectively bridge the spectral gap between satellite and terrestrial data. An additional consideration for the high-frequency gravity signals is induced by the topography, and the residual terrain model (RTM) is used to recover the omission errors effect of the combined GGM. In addition, to facilitate practical implementation of the GBVP approach, the effects of the indirect bias term, the spectral accuracy of the GGM, and the systematic levelling errors and distortions in estimations of the vertical datum parameters are investigated in this study. Finally, as a result of the GBVP solution based on the combined DIR_R6/EGM2008 model, RTM, and residual gravity, the geopotential values of the North American Vertical Datum of 1988 (NAVD88), the Australian Height Datum (AHD), and the Hong Kong Principal Datum (HKPD) are estimated to be equal to 62636861.31 ± 0.96, 62653852.60 ± 0.95 and 62636860.55 ± 0.29 m2s−2, respectively. The vertical offsets of NAVD88, AHD, and HKPD with respect to the global geoid are estimated as −0.809 ± 0.090, 0.082 ± 0.093, and −0.731 ± 0.030 m, respectively.

scholarly journals Wildfire Detection Probability of MODIS Fire Products under the Constraint of Environmental Factors: A Study Based on Confirmed Ground Wildfire Records

2019 ◽  
Vol 11 (24) ◽  
pp. 3031 ◽  
Author(s):  
Lingxiao Ying ◽  
Zehao Shen ◽  
Mingzheng Yang ◽  
Shilong Piao
Keyword(s):  
Environmental Factors ◽  
Detection Probability ◽  
Ground Level ◽  
Omission Error ◽  
Limiting Factor ◽  
Commission Error ◽  
Fire Size ◽  
Weather Factors ◽  
Local Conditions ◽  
Wildfire Occurrence

The Moderate Resolution Imaging Spectroradiometer (MODIS) has been widely used for wildfire occurrence and distribution detecting and fire risk assessments. Compared with its commission error, the omission error of MODIS wildfire detection has been revealed as a much more challenging, unsolved issue, and ground-level environmental factors influencing the detection capacity are also variable. This study compared the multiple MODIS fire products and the records of ground wildfire investigations during December 2002–November 2015 in Yunnan Province, Southwest China, in an attempt to reveal the difference in the spatiotemporal patterns of regional wildfire detected by the two approaches, to estimate the omission error of MODIS fire products based on confirmed ground wildfire records, and to explore how instantaneous and local environmental factors influenced the wildfire detection probability of MODIS. The results indicated that across the province, the total number of wildfire events recorded by MODIS was at least twice as many as that in the ground records, while the wildfire distribution patterns revealed by the two approaches were inconsistent. For the 5145 confirmed ground records, however, only 11.10% of them could be detected using multiple MODIS fire products (i.e., MOD14A1, MYD14A1, and MCD64A1). Opposing trends during the studied period were found between the yearly occurrence of ground-based wildfire records and the corresponding proportion detected by MODIS. Moreover, the wildfire detection proportion by MODIS was 11.36% in forest, 9.58% in shrubs, and 5.56% in grassland, respectively. Random forest modeling suggested that fire size was a primary limiting factor for MODIS fire detecting capacity, where a small fire size could likely result in MODIS omission errors at a threshold of 1 ha, while MODIS had a 50% probability of detecting a wildfire whose size was at least 18 ha. Aside from fire size, the wildfire detection probability of MODIS was also markedly influenced by weather factors, especially the daily relative humidity and the daily wind speed, and the altitude of wildfire occurrence. Considering the environmental factors’ contribution to the omission error in MODIS wildfire detection, we emphasized the importance of attention to the local conditions as well as ground inspection in practical wildfire monitoring and management and global wildfire simulations.

scholarly journals A New Method for Vertical Deformation Detection Using Survey Control Networks

2009 ◽  
Vol 4 (1) ◽  
pp. 14
Author(s):  
Mudathir Omer Ahmed
Keyword(s):  
Least Squares ◽  
Confidence Level ◽  
Specific Area ◽  
New Method ◽  
Control Network ◽  
Vertical Deformation ◽  
Control Networks ◽  
Vertical Control ◽  
Vertical Deformations ◽  
Step Localization

Usually, the Survey control networks are used for deformation detection in a specific area using observations taken at different epochs. Where the coordinates obtained from two epochs, using least squares technique, are compared in order to assess if a deformation of a specified magnitude exists. Traditionally, the global congruency test is carried out so as to detect if the area of the network has undergone any movement (uplift or subsidence) due to natural or manmade causes. As a next step, localization methods are used to determine deformations at specific points in case there are changes in shape. In this research a new method is developed to establish deformations at specific points directly. The method is tested using a vertical control network simulated at various epochs of observation. The results obtained are compared with those obtained by another used method. Results obtained using this method indicate that vertical deformations greater than 0.03m using a precision of observation less than 10 can be detected at a minimum significant level of 0.05 (95% confidence level).

scholarly journals Preliminary Unification of Kronsztadt86 Local Vertical Datum with Global Vertical Datum

2015 ◽  
Vol 97 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Adam Łyszkowicz ◽  
Joanna Kuczyńska-Siehień ◽  
Monika Biryło
Keyword(s):  
Systematic Error ◽  
Sufficient Accuracy ◽  
Satellite Networks ◽  
Satellite Observations ◽  
Gravity Potential ◽  
Best Value ◽  
Vertical Datum ◽  
Normal Heights ◽  
Low Efficiency ◽  
Local Vertical Datum

AbstractThe study concerns computation of the gravity potential difference between the Kronsztadt86 datum and the global vertical datum. This method is based on the use of ellipsoidal heights from satellite observations, normal heights obtained from the conducted leveling campaign and quasigeoid/ellipsoid separations computed based on the EGM2008 model. The obtained results indicate that there are substantial differences in the estimated value of the parameter ΔW, computed from three different satellite networks: POLREF, EUVN-DA and ASG-EUPOS. The parameter was determined with sufficient accuracy and the applied systematic error model has low efficiency. The computations reveal that the best value of ΔW for the territory of Poland is 0.43 m2s-2.

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