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1.
Virtual differential GPS based on SBAS signal 总被引：2，自引：0，他引：2
In order to access the satellite-based augmentation system (SBAS) service, the end user needs access to the corresponding geostationary earth orbit (GEO) satellites that broadcast the augmentation information for the region. This is normally not a problem for aviation and maritime applications, because an open sky is typically available for such applications. However, it is difficult to access the GEO satellites directly at high latitudes for land applications because of the low elevation angles to the GEO satellites (e.g., 4–22° in Finland to the European geostationary navigation overlay services [EGNOS] GEO satellites). Results from a driving test of 6,100 km in Finland show that the EGNOS GEO satellites can be accessed in only 51.8% of the driving routes. Furthermore, it is also difficult to access the GEO satellites from city canyons, because the high buildings block the GEO signals. This article presents a solution to solve this problem by creating virtual differential GPS (DGPS) reference stations using the SBAS signal in space (SIS). The basic concept is to convert the SBAS signal to Radio Technical Commission for Maritime Services (RTCM) signals, and broadcast the converted RTCM signals over the wireless Internet using the Internet radio technology. Therefore, access to the SBAS service will not be limited by low elevation angles to the GEO satellites because the converted RTCM data streams are disseminated over the wireless Internet. Furthermore, the SBAS service can then be accessed via a legacy DGPS receiver. Two test cases have been carried out with the prototype system developed by the Finnish Geodetic Institute. The test results showed that the positioning accuracy of the virtual DGPS solution was about 1–2 m at 95%, which was similar to that of the standard WAAS/EGNOS solution. The positioning accuracy was not degraded, compared to that of the standard wide area augmentation system–European geostationary navigation overlay services (WAAS/EGNOS) solution, as long as the distance between the rover receiver and the virtual DGPS reference station was less than 150 km. A preliminary driving test of 400 km carried out in southern Finland showed that the availability of the virtual DGPS solutions was 98.6% along the driving route. 相似文献
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简要介绍了DGPS RTK技术的基本原理和作业流程，阐明了该技术在近海平台定位中的适用性，并以某近海大桥主桥墩平台定位为例，讨论了利用该技术进行平台定位实测的主要技术难点与实际工作过程，通过对实测数据成果的分析，得出了一些有益的结论。 相似文献
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In recent years the importance of real-time positioning and navigation with the Global Positioning System (GPS) has grown
rapidly. Starting from the establishment of differential GPS (DGPS) reference stations for marine and land navigation, new
users and applications have emerged that resulted in a high demand for the establishment of a high-density network of reference
stations around the world. Many countries have established their own DGPS service, which is either governmentally or commercially
owned. These services are referred to as Local Area DGPS Systems (LADGPS). However, the costs for the establishment and maintenance
of a dense network of reference stations are very high. Therefore Wide Area DGPS Systems (WADGPS) are being developed to overcome
the main drawbacks of LADGPS. In this case, only a few reference stations are used to cover a large area, such s a continent
like Europe. To achieve high positioning accuracies, real-time modeling of the main error sources for long-range baselines
is required as errors in the satellite orbit and ionospheric refraction do not cancel entirely in double differencing. In
this article, a real-time correction model based on the Kalman filter for WADGPS and networked LADGPS services is discussed
and results of field tests in a WADGPS network in Europe are presented. ? 2000 John Wiley & Sons, Inc. 相似文献
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This article investigates the use of the Internet as the communication link between the base and rover stations for the development
of an Internet-based Real-Time Kinematic (RTK) system. An Internet-based RTK system has many advantages if compared to current
radio-based RTK systems. To validate the concept, a prototype system has been developed and tested in both static and kinematic
modes. The results indicated that the base differential data latency is in the range of about 1 second and the RTK positioning
accuracy is at the centimeterl level. ? 2002 Wiley Periodicals, Inc. 相似文献
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The latest evolution in digital wireless technology, third-generation (3G) Code Division Multiple Access/Single Carrier (CDMA2000/1X) wireless network, is applicable for transmitting real-time kinematic (RTK) GPS correction messages. Fast and reliable, publicly available wireless networks, combined with highly accessible Internet connectivity, allows the multicasting of messages to mobile users, who are no longer restricted to traditional private UHF wireless networks. Nationwide public wireless network systems continue to expand and can provide an inexpensive infrastructure for the emerging multi-reference network system. Transmission performance via the Internet-based CDMA2000/1X outperforms UHF technology in transmission throughput and latency, as well as in the RTK initialization time and positional accuracy. 相似文献
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为确保基于VRS的网络RTK定位性能,提高VRS的服务质量,本文系统地构建了面向海量并发用户服务的格网化VRS方法,建立了VRS格网的两种划分方法。顾及电离层延迟的空间相关特性,选定中纬度和低纬度两个区域的CORS网络进行试验测试,分析并确定不同区域条件下,格网化VRS的有效服务间距。结果表明:在中纬度地区和低纬度地区,格网VRS有效服务间距限值分别为12 km和7 km。与非格网化VRS(以标准定位服务结果建立)相比,可大幅度降低VRS产生和计算负荷,有效提升服务器对海量用户的服务能力。 相似文献
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RTK技术具有实时高效等特点,使其在测量与导航领域得以广泛应用。传统的RTK数据传输模式为电台数传链路,其时空局限性的特点制约了RTK技术应用的进一步发展。随着Internet网络应用的蓬勃发展,GPS差分定位与RTK定位测量模式也相应产生巨大的变革,网络技术为GPSRTK技术提供了新的突破点:结合Inter-net技术来进行GPS高精度实时动态定位。本文通过分析TCP/IP和UDP两种Internet传输协议、GPS差分数据RTCM类型和字节大小,及其在两种网络协议下数据传输速度的比较,对应用Internet作为差分GPS数据传输方式进行测试与分析。 相似文献
12.
GPS/VRS 卫星定位服务网络建设与精度评定 总被引：13，自引：0，他引：13
虚拟参考站技术是近几年发展起来的,集Internet、无线通讯、计算机网络和GPS于一体的卫星定位技术。成都虚拟参考站卫星定位服务系统的建设,在设计上可满足全天候地向大成都地区用户提供厘米级实时动态定位服务。为了对该系统的实际定位精度进行客观的评价,从2 0 0 4年7月开展,历时两个月,全面完成了成都虚拟参考站卫星定位服务系统的精度评定工作,结果表明:在网内,水平方向上的精度可达2 .5cm ,垂直方向上的精度为4 . 5cm ,精度分布均匀;在网外,未模型化的距离相关误差的残余逐步增大,特别是距离网络中心大于1 2 0km以上时,定位精度开始衰减,为分米级。 相似文献
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GNSS区域参考站网可为大范围PPP和RTK终端用户提供快速精密定位服务,然而不同技术体制下的误差影响因素及服务模式不同,服务端数据处理方法及终端定位性能也会有所差异。本文在实现参考站非差模糊度固定的基础上,给出了基于区域参考站网的PPP及RTK一体化服务方法,并对两种技术体制的终端定位效果进行了全面评估。采用西北某省站间距约100 km的CORS站网数据进行试验分析,结果表明,采用区域参考站网解算的整数钟/UPD产品进行PPP固定解动态定位时精度较高,水平方向RMS可达0.5 cm,区域大气改正数可以显著提升定位终端的初始化速度,对于PPP和RTK,60.0%和87.7%的时段单历元即可得到固定解。需要注意的是,基于VRS模式的RTK定位等价于大气强约束,在大气建模精度较差时定位精度会显著下降,而采用虚拟大气约束的PPP-RTK定位精度几乎不受影响。 相似文献
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Robert Odolinski 《GPS Solutions》2012,16(2):147-155
Temporal correlation in network real-time kinematic (RTK) data exists due to unmodeled multipath and atmospheric errors, in
combination with slowly changing satellite constellation. If this correlation is neglected, the estimated uncertainty of the
coordinates might be too optimistic. In this study, we compute temporal correlation lengths for network RTK positioning, i.e.,
the appropriate time separation between the measurements. This leads to more realistic coordinate uncertainty estimates, and
an appropriate surveying strategy to control the measurements can be designed. Two methods to estimate temporal correlation
lengths are suggested. Several monitor stations that utilize correction data from two SWEPOSTM Network RTK services, a standard service and a project-adapted service with the mean distance between the reference stations
of approximately 70 and 10–20 km, are evaluated. The correlation lengths for the standard service are estimated as 17 min
for the horizontal component and 36–37 min for the vertical component. The corresponding estimates for the project-adapted
service are 13–17 and 13–16 min, respectively. According to the F test, the proposed composite first-order Gauss–Markov autocovariance function shows a significantly better least-squared
fit to data compared to the commonly used one-component first-order Gauss–Markov model. A second suggested method is proposed
that has the potential of providing robust correlation lengths without the need to fit a model to the computed autocovariance
function. 相似文献
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Ajay Dashora B. Sreenivas Bharat Lohani Javed N. Malik Afroz Ahmad Shah 《Journal of the Indian Society of Remote Sensing》2006,34(2):153-160
Use of high-resolution and historic CORONA satellite photographs for mapping and other purposes requires Ground Control Points
(GCPs), as ephemeris data and image parameters are not available. However, the alterations in landscape in last 34 years (i.e., since the acquisition of these photographs) prevent identification and collection of large number of GCPs in the field.
This paper presents a methodology for collection of GCPs for CORONA photographs. The advantages and limitations of the methodology
are discussed. For a study site, situated in Siwaliks and Lower Himalayas, the GCPs were identified in CORONA photographs
and their WGS84 coordinates were estimated through a process of datum transformation and georeferencing. Estimated GCP coordinates
from the topo sheets and 2D and 3D views of photographs, helped in identifying the GCP locations in field, which were observed
using DGPS. Investigations were carried out to relate Differential Global Positioning System (DGPS) accuracy with base line
length and time of observation. Abase line of 350 km and half an hour observation were found appropriate to yield accuracy
in GCP collection by DGPS method, which conforms to CORONA resolution of 3 m. 相似文献
18.
Alternatives to current GPS-RTK services and some implications for CORS infrastructure and operations 总被引：1，自引：1，他引：1
Chris Rizos 《GPS Solutions》2007,11(3):151-158
The justification for the establishment of CORS networks was initially in support of geodesy and other geoscientific applications at the global and regional level. However, increasingly GPS CORS network operators have sought ways of making their network infrastructure the basis of a profitable business. This has arisen with the introduction of real-time centimeter-level accuracy services, carrier phase-based modes of operation generally referred to as GPS-RTK (real-time kinematic). One approach is to try to recruit a core group of users who are prepared to pay for the GPS-RTK services. But this is only feasible if the number of users, and the fees that are charged, are sufficient to generate a reasonable return-on-investment (ROI). This ROI (or at the very least “cost-recovery”) is important for many network operators in order that they may provide for the maintenance and upgrade of the CORS infrastructure. On the other hand, there are those who advocate that there is no need to recoup CORS investment, that the installed GPS receivers should be seen as public infrastructure in a similar manner to roads, bridges, etc. This paper discusses some new business and operational models for GPS-RTK services. These include models for the establishment and operation of CORS infrastructure, service provision, business cases, and options for value-added services beyond the standard GPS-RTK service. One concept is based on a “client–server” model. Currently GPS-RTK service providers have no control over the quality of the results computed by users. This makes it difficult for them to justify charging for their services. What if instead of broadcasting RTK corrections and placing the onus of obtaining a final solution on the user and his equipment, the user’s coordinates are determined by the service provider? Putting the computational effort on the server side will justify more easily the charging of users for a value-added product: an accurate and quality assured coordinate in the local reference frame. This paper describes the client–server concept as well as possible business models that may underpin such a service model. These models include some derived from mobile telephony and service/hospitality businesses. Furthermore, with the projected proliferation of independent, competitive GPS-RTK services, the concept of a GPS data or service “broker” is worth exploring. 相似文献
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随着测绘技术的不断进步,GPS实时动态定位技术(RTK)在测绘领域的应用日益广泛,而基于VRS(虚拟参考站Virtual Reference Station)技术的出现,更是为RTK测量提供了新的技术平台,给测量行业带来了革命性的变化。本文结合实例简要介绍了基于VRS的RTK在测绘领域的应用,阐述了其优越性和不足之处。 相似文献
20.
基于DREAMNET的GPS/BDS/GLONASS多系统网络RTK定位性能分析 总被引：1，自引：1，他引：0
随着BDS系统完成亚太地区组网、GLONASS系统再次实现满星座部署以及GPS系统的现代化,多系统集成已逐步成为网络RTK技术的发展趋势。本文结合笔者所在课题组自主研发的网络RTK数据处理系统DREAMNET,对不同卫星系统组合模式下的定位精度进行比较分析。试验结果表明,GPS/BDS/GLONASS网络RTK和GPS/BDS网络RTK的定位精度最高,GPS、BDS单系统网络RTK次之。此外,随着高度角的增加,GPS单系统网络RTK的可用性显著降低,而GPS/BDS/GLONASS网络RTK在高度角为40°时依然可以在99.84%的时间里提供水平精度0.01 m、高程精度0.025 m的定位服务。最后,对15 d的定位结果进行统计,包括不依赖GPS系统的BDS和BDS/GLONASS在内的6种组合方式皆可达到水平0.01 m、高程0.025 m的定位精度,其中GPS/BDS/GLONASS网络RTK则可以得到水平0.006 m、高程0.015 m的定位精度,证明DREAMNET的定位精度和稳定性完全可以满足测绘作业的需要。 相似文献