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This paper treats the problem of how to transform from global datum, for example, from the International Terrestrial Reference System (ITRS), to a local datum, for example, regional or national, for the practical case of the Lambert projection of the sphere or the ellipsoid-of-revolution to the cone. We design the two projection constants n(ϕ1, ϕ2) and m(ϕ1) for the Universal Lambert Conic projection of the ellipsoid-of-revolution. The task to transform from a global datum with respect to the ellipsoid-of-revolution EA,B2 to local datum with respect to the alternative ellipsoid-of-revolution Ea,b2, without local ellipsoidal height, is solved by an extended numerical example. Ideas in this paper could be of interest to those working with maps and coordinates transformation from global geodetic datum to local geodetic datum and vice versa, under the Universal Lambert Conic projection, and applicable to precise positioning and navigation, boundary demarcation and determination in the marine environment. 相似文献
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Nigel R. L. Gooding 《Marine Geodesy》2013,36(3-4):197-203
Abstract The historical development of positioning in relation to the nautical chart is described. Present nautical charts are largely based on geodetic surveys which date from the nineteenth and early twentieth centuries. This gave rise to the use of many local datums and there has been a need to provide the mariner with information to enable him to transfer his position from one chart to an adjacent one on a different datum. The availability of the Global Positioning System (GPS) and the World Geodetic System 1984 (WGS84) datum enables positioning on a single worldwide datum to become a reality. The important factors affecting the adoption of WGS84 as the datum for nautical charts—namely, data availability and the practical and political considerations—are discussed. New developments in the use of nautical charts, the electronic chart display and information systems, and the delineation of international boundaries and territorial limits all give rise to the requirement for improved positional accuracies. Recent experience in the use of GPS both in the provision of control for shore stations of electronic position‐fixing systems and the provision of position for hydrographic surveys is briefly discussed. 相似文献
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Hasanuddin Z. Abidin S. Sutisna T. Padmasari K. J. Villanueva J. Kahar 《Marine Geodesy》2013,36(4):291-304
Indonesia has maritime boundaries with 10 countries namely: Australia, Timor Leste, Papua New Guinea (PNG), Palau, Philippines, Vietnam, Thailand, Malaysia, Singapore, and India. Many treaties have been ratified concerning these boundaries. Unfortunately, many coordinates of boundary points mentioned in the treaties are not clear in relation to their geodetic datum. The uncertainty in geodetic datum of boundary points introduces complications and problems in spatial management of Indonesia's maritime boundaries, since it can displace the boundary lines from their assumed true location. This study investigates the possible original geodetic datums for the maritime boundaries between Indonesia and neighboring countries, in the case they are not explicitly stated in the treaties. The displacements of boundaries in WGS84 datum are generally in the order of a few hundred meters, i.e., about 200 to 400 m, depending on the assumed original geodetic datum being considered. These boundary displacements are spatially advantageous for Indonesia in some cases and also disadvantageous in others. The study will sum up with some conclusions and recommendations. 相似文献
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Hasanuddin Z. Abidin S. Sutisna T. Padmasari K. J. Villanueva J. Kahar 《Marine Geodesy》2005,28(4):291-304
Indonesia has maritime boundaries with 10 countries namely: Australia, Timor Leste, Papua New Guinea (PNG), Palau, Philippines, Vietnam, Thailand, Malaysia, Singapore, and India. Many treaties have been ratified concerning these boundaries. Unfortunately, many coordinates of boundary points mentioned in the treaties are not clear in relation to their geodetic datum. The uncertainty in geodetic datum of boundary points introduces complications and problems in spatial management of Indonesia's maritime boundaries, since it can displace the boundary lines from their assumed true location. This study investigates the possible original geodetic datums for the maritime boundaries between Indonesia and neighboring countries, in the case they are not explicitly stated in the treaties. The displacements of boundaries in WGS84 datum are generally in the order of a few hundred meters, i.e., about 200 to 400 m, depending on the assumed original geodetic datum being considered. These boundary displacements are spatially advantageous for Indonesia in some cases and also disadvantageous in others. The study will sum up with some conclusions and recommendations. 相似文献
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High precision geoid models HKGEOID-2000 for Hong Kong and SZGEOID-2000 for Shenzhen, China, have been developed with a hybrid approach of so-called sequential processing, using high precision GPS/leveling data, land and sea gravity anomalies, and digital terrain models. These two local geoid models have the same 1-km resolution. The estimated accuracy (external accuracy) is better than 1.7 cm for HKGEOID-2000 and 1.4 cm for SZGEOID-2000. Some common areas are covered by HKGEOID-2000 and SZGEOID-2000. So these two geoid models, along with high quality GPS/leveling data collected on the overlapping areas, can be used to detect the systematic bias between HKGEOID-2000 and SZGEOID-2000, as well as the difference between Hong Kong Principal Datum and 1956 yellow sea height datum of China, yielding RMS errors of 1.011 m and 1,003 m, respectively. Moreover, HKGEOID-2000, along with GPS ellipsoidal heights, is employed to determine the errors of the “orthometric heights” from purely trigonometric heighting, yielding an RMS error of 0.102 m. The combination of SZGEOID-2000 and GPS ellipsoidal heights has been used to replace the traditional spirit leveling and mapping, called GPS mapping. 相似文献
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High precision geoid models HKGEOID-2000 for Hong Kong and SZGEOID-2000 for Shenzhen, China, have been developed with a hybrid approach of so-called sequential processing, using high precision GPS/leveling data, land and sea gravity anomalies, and digital terrain models. These two local geoid models have the same 1-km resolution. The estimated accuracy (external accuracy) is better than 1.7 cm for HKGEOID-2000 and 1.4 cm for SZGEOID-2000. Some common areas are covered by HKGEOID-2000 and SZGEOID-2000. So these two geoid models, along with high quality GPS/leveling data collected on the overlapping areas, can be used to detect the systematic bias between HKGEOID-2000 and SZGEOID-2000, as well as the difference between Hong Kong Principal Datum and 1956 yellow sea height datum of China, yielding RMS errors of 1.011 m and 1,003 m, respectively. Moreover, HKGEOID-2000, along with GPS ellipsoidal heights, is employed to determine the errors of the “orthometric heights” from purely trigonometric heighting, yielding an RMS error of 0.102 m. The combination of SZGEOID-2000 and GPS ellipsoidal heights has been used to replace the traditional spirit leveling and mapping, called GPS mapping. 相似文献
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沿海区域的测绘资料主要采用1954年北京坐标系、1980西安坐标系和2000国家坐标系(旧称WGS84坐标系),造成使用不便,需要构建这些系统之间的转换关系。不同方法和不同分区的大量试算表明,1980西安坐标系与WGS84坐标系可以采用7参数转换模型,3个分区和5个分区的精度都能达到0.5 m,其中5个分区的精度较好。由于1954年北京坐标系的特殊性,简单的7参数模型不能确保系统的转换精度,1954年北京坐标系与WGS84坐标系最好采用曲面拟合方法实现坐标转换,整个沿海区域采用6个分区,精度可以达到0.5 m以内的转换要求。 相似文献
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随着GPS技术的发展，具有RTK功能的GPS接收机不但在平面位置上可以达到厘束级，而且以WGS84为参考椭球的垂直高程也可以达到厘束级，因而被广泛地应用于海岸带测量中。本文介绍了RTKGPS在海域勘界、无验潮模式水深测量方面的一些具体应用。 相似文献
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Tide gauge data is important for determining global or local sea level rise with respect to a global geocentric reference frame. Data from repeated precise levelling connections between the tide gauges and a series of coastal and inland benchmarks, including Continuous GPS (CGPS) benchmarks, are used to determine the stability of tide gauges at 12 locations in the South Pacific. The method for determining this stability is based on a constant velocity model which minimises the net movement amongst a set of datum benchmarks surveyed since the installation of the tide gauges. When assessed at a 95% confidence interval, and with the exception of the Solomon Islands, none of the tide gauges were found to be in motion relative to their CGPS benchmarks. The Solomon Islands estimate is considered to be unreliable since the CGPS benchmark was recently established and has been surveyed fewer than three times. In Tonga and Cook Islands, the tide gauges were found to be disturbed or affected by survey errors whereas the Vanuatu results were affected by earthquakes. 相似文献
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针对远离大陆的海岛礁地形测绘与高程基准转换困难的问题,基于ADS40航摄系统获取远离大陆的海岛礁区域遥感影像,按照GPS差分无地面控制点的空中三角测量模式实现海岛礁的地理定位,选择高精度的卫星测高模型实现海岛礁区域的高程基准转换。在某海域进行了ADS40测量作业与高程基准转换试验,结果表明,无地面控制点空中三角测量的平面精度达到0.587m;基于卫星测高模型进行垂直基准转换的精度与同步验潮水位观测法得到的高程传递精度相当。 相似文献
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为了评价GPS与VLBI这两种空间技术测定的地心坐标的真正实现精度,选择使用它们的并置站坐标数据,在进行了历元改正和偏心改正后,计算了这两种技术实现的参考架的转换参数,并分析了它们坐标不符值的中误差,得出GPS与VLBI这两种技术实现的参考架的外符合精度在1cm之内,表明了GPS与VLBI这两种技术测定的地心坐标精度已经达到毫米量级。 相似文献
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Researches on breaking-induced currents by waves are summarized firstly in this paper. Then, a combined numerical model in orthogonal curvilinear coordinates is presented to simulate wave-induced current in areas with curved boundary or irregular coastline. The proposed wave-induced current model includes a nearshore current module established through orthogonal curvilinear transformation form of shallow water equations and a wave module based on the curvilinear parabolic approximation wave equation. The wave module actually serves as the driving force to provide the current module with required radiation stresses. The Crank-Nicolson finite difference scheme and the alternating directions implicit method are used to solve the wave and current module, respectively. The established surf zone currents model is validated by two numerical experiments about longshore currents and rip currents in basins with rip channel and breakwater. The numerical results are compared with the measured data and published numerical results. 相似文献
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The published global ocean tide models show good agreement in deep oceans and exhibit differences in complex coastal areas, along with subsequent Ocean Tide Loading Displacement (OTLD) modeling differences. Meanwhile, OTLD parameters (amplitudes and phase lags) derived by Global Positioning System (GPS) Precise Point Positioning (PPP) approach need long time to converge to a stable state and show poor precision of S2, K1, and K2 constituents. Based on the fact that no constraint is imposed in the current kinematic solution, a new method is put forward, in which global ocean tide model predictions are taken as the priori information constraints to speed up the convergence rate and improve the accuracy of the GPS-derived OTLD parameters. First, the data of tide gauge from 01 January 2014 to 31 December 2016 are used to generate the harmonic parameters to evaluate the accuracy of six global ocean tide models and a regional ocean tide model (osu.chinesea.2010). Osu.chinesea.2010 model shows good agreement with the tide gauge results, while NAO99b model presents relatively large difference. The predictions from osu.chinesea.2010 and NAO99b model are employed as reference and the prior information, respectively. Second, continuous observations of 12 GPS sites during 2006–2013 in Hong Kong are collected to generate three dimensional OTLD amplitudes and phase lags of eight constituents using PPP with prior information constraints approach and harmonic analysis. Third, comparing the convergence time of eight constituents from PPP without and with priori information constraints approaches, the results show that the new method can significantly improve the convergence rate of OTLD amplitude estimates which obtain a certain level of stability seven years earlier than that derived by the PPP without priori information constraints. Precision of OTLD parameters derived by the new method is about 1 mm. By comparing with the precision of single PPP approach, the accuracy of eight constituents has been improved, especially for S2, K1, and K2 constituents. Finally, through comparing the different correction effects of OTLD estimates on the coordinates and their time series of the ground GPS stations, the results show that OTLD estimates derived by the new approach have similar influence as the osu.chinasea.2010 ocean tide model. The new method provides an effective means to improve the convergence and precision of the GPS-derived OTLD parameters, and achieve a similar correction as the high precision ocean tide model. 相似文献
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GPS测量直接获得点位的精确三维坐标,通过空间直角坐标系、大地坐标系、站心地平直角坐标系、站心极坐标系等一系列转换,再加入大气折光差改正和垂线偏差改正,就可以快速获得设备标校所需的精确基准。与采用常规测量方法、分别计算设备标校基准相比,不仅大大减少了工作量,还提高了计算结果的精度。 相似文献
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