Post on 06-Jul-2015
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Sichuan Network GPS
Service Introduction
Sichuan Seismological Bureau 2006.8
Review of PositioningReview of Positioning
► Single PointSingle PointUsing only one receiver to Using only one receiver to receive signal (C/A code). receive signal (C/A code). Position information is calculated Position information is calculated independently.independently.Advantage:Advantage:
Distance:Distance: UnlimitedUnlimitedCommunication: No neededCommunication: No needed
Complexity: LOWComplexity: LOWDisadvantage:Disadvantage:
Accuracy: 10M, LOWAccuracy: 10M, LOW
► Single Base DifferentiationSingle Base DifferentiationOne receiver as base One receiver as base station and another as station and another as rover station. Rover rover station. Rover receives the position receives the position correction data to improve correction data to improve its accuracy.its accuracy.DGPS AND RTKDGPS AND RTKThe accuracy of DGPS is The accuracy of DGPS is 3m(C/A code) or 50cm 3m(C/A code) or 50cm (C/A code + L1). (C/A code + L1). RTK(L1,L2) can reach 3cm RTK(L1,L2) can reach 3cm accuracy.accuracy.
Note :Need to set up a base station. Note :Need to set up a base station. Need a data link for communication.Need a data link for communication.
Single base differentiation is base on the high correlation of Single base differentiation is base on the high correlation of GPS signal on high correlation of GPS signals in nearby area. GPS signal on high correlation of GPS signals in nearby area. Taking the data link in account, the distance between rover Taking the data link in account, the distance between rover station and base station is less than 15km. station and base station is less than 15km.
Problem:Problem:
Uneven Accuracy—degrade as distance increaseUneven Accuracy—degrade as distance increaseLow reliability—Low reliability—Single reference; No integrity monitoring; Single reference; No integrity monitoring; May import error when setting reference stationMay import error when setting reference station
Frequent resetting base stations.Frequent resetting base stations.
Network GPSNetwork GPS
As the technology of satellite positioning, wireless As the technology of satellite positioning, wireless communication and computer networks process, in communication and computer networks process, in the 1990s, Network RTK was proposed. In early the 1990s, Network RTK was proposed. In early 2000s, as commercial software of Network RTK being 2000s, as commercial software of Network RTK being developed, Realtime differentiation technology is developed, Realtime differentiation technology is moving rapidly into multi-base Network RTK. The moving rapidly into multi-base Network RTK. The most interested is virtual reference station (VRS) most interested is virtual reference station (VRS)
Formation:Formation:1 A base station network 1 A base station network
made by more than 2 made by more than 2 running GPS base running GPS base stations.stations.
Number of stations:≥3Number of stations:≥3
Distance:50km—70kmDistance:50km—70km
FormationFormation22 A control center A control center
running Network RTK running Network RTK system softwaresystem software
FormationFormation33 Reliable data linkReliable data link
AdvantageAdvantage1 Increase working range, improve efficiency1 Increase working range, improve efficiency2 Significantly lower system error and initiation 2 Significantly lower system error and initiation
time, improve accuracytime, improve accuracy3 All users are in the same coordinate system3 All users are in the same coordinate system4 Personal surveying system, no local reference 4 Personal surveying system, no local reference
station neededstation needed
Introduction to Sichuan Province Introduction to Sichuan Province Network GPS Service SystemNetwork GPS Service System
Reference Station Reference Station NetworkNetwork
13 Stations13 StationsDistance:Distance: Min 42kmMin 42km Max 132kmMax 132km Avg. 86km Avg. 86km
交换机
中国地
震局DDN
Lan1 Lan2
成
都
郫
县
仁
寿
中
江
简
阳
邛
崃
数据分流器
系统主交换机MP9400
三楼通讯机房
泸州
宜宾
乐山
内江
绵阳
雅
安
数据库
(1)
GPSNet(2)
GPSNet(1)
GPStream 数据库
(2)
SCGNet
系统主交换机
系统主路由器
交换机
八楼数据中心
GPSNet路由器 SCGNet路由器
Internet
网桥卡
Control CenterControl Center
► Control center and Control center and users communicate users communicate thought Internet and thought Internet and wireless networks. wireless networks.
► For wireless networks, For wireless networks, system support system support GPRS/CDMA/GSMGPRS/CDMA/GSM 。。 ..
► Terminals require Terminals require wireless support wireless support hardware such as hardware such as GPRS/CDMA modules GPRS/CDMA modules and GSM Modemand GSM Modem
Sichuan Province Network GPS Service SystemSichuan Province Network GPS Service System
►The system RTK service area 4.5 万 km 2, covering
major developed area. RTK accuracy±2.5cm(better than±3.0cm) RTD service area36 万 km2
RTD accuracy ±33cm(better than±50cm)
► To reach the accuracy 0f ±3cm in Chendu, 44 GPS/Geodesy sites are set in 12km distance grid. 8 GPS/Geodesy sites are set randomly in the area for counter check
► To reach the accuracy of ±5cm in Ya’an, 20 GPS/Geodesy sites are set in 10km distance grid.
► All sites perform a 4-hour GPS static observation and level 2 geodesy observation
GGeodesyeodesy Determination Determination
成都地区外检验不符值的成都地区外检验不符值的
Max 5.7cmMax 5.7cm 平均差值为平均差值为 2.1cm2.1cm 中误差为中误差为 ±2.5cm±2.5cm 。。
1 0 3 . 5 0 1 0 3 . 7 5 1 0 4 . 0 0 1 0 4 . 2 5 1 0 4 . 5 0 1 0 4 . 7 53 0 . 0 0
3 0 . 2 5
3 0 . 5 0
3 0 . 7 5
3 1 . 0 0
3 1 . 2 5
³ É ¶ ¼ Ê Ð × î Ö Õ Ë Æ ´ ó µ Ø Ë ® × ¼ Ã æ µ È Ö µ Ï ß Í ¼µ ¥ Î » £ º Ã ×
Í ¼3
雅安地区外外检验不符值的
最大值为 6.2cm 平均差值为 2.5cm 中误差为±3.2cm 。
1 0 2 . 8 5 1 0 2 . 9 0 1 0 2 . 9 5 1 0 3 . 0 0 1 0 3 . 0 5 1 0 3 . 1 0 1 0 3 . 1 5 1 0 3 . 2 0 1 0 3 . 2 52 9 . 7 5
2 9 . 8 0
2 9 . 8 5
2 9 . 9 0
2 9 . 9 5
3 0 . 0 0
3 0 . 0 5
3 0 . 1 0
3 0 . 1 5
3 0 . 2 0
3 0 . 2 5
Ñ Å ° ² Ê Ð × î Ö Õ Ë Æ´ ó µ Ø Ë ® × ¼Ã æµ È Ö µ Ï ß Í ¼µ ¥ Î » £ º à ×
Í ¼3
System Accuracy Evaluation System Accuracy Evaluation
►Two accuracy evaluationsTwo accuracy evaluations First evaluation after 4 GPS reference sites and First evaluation after 4 GPS reference sites and
control center are constructedcontrol center are constructed Second evaluation done after 12 reference Second evaluation done after 12 reference
stations are networkedstations are networked
► First evaluation uses RTK accuracy from GPSNet First evaluation uses RTK accuracy from GPSNet systemsystem
►Evaluation contentEvaluation content RTK/RTD accuracy inside the network(20 km RTK/RTD accuracy inside the network(20 km
from border )from border ) Analysis of uniformity of accuracy inside the Analysis of uniformity of accuracy inside the
networknetwork Analysis of distance correlation of accuracy Analysis of distance correlation of accuracy
outside the networkoutside the network
Attenuation with distance in N axis (m) Attenuation with distance in E axis (m)
Attenuation with distance in height (m)
Result of the two evaluationsResult of the two evaluations
By using Sichuan Network GPS Positioning By using Sichuan Network GPS Positioning ServiceService
The RTK accuracyThe RTK accuracy Better than Better than ±2.5cm±2.5cm in horizontal direction and in horizontal direction and
even inside networkeven inside network Attenuate rapidly 50 km outside the networkAttenuate rapidly 50 km outside the network
Features and ApplicationsFeatures and Applications
1.Combination of fix stations and 1.Combination of fix stations and portable devices. The system not only portable devices. The system not only monitors active rift in Plain Chendu monitors active rift in Plain Chendu and southern area of Sichuan Province and southern area of Sichuan Province but also helps in scientific but also helps in scientific researches and commercial uses. researches and commercial uses.
With 86km average-distance With 86km average-distance between reference stations, the between reference stations, the network GPS system still satisfy network GPS system still satisfy the design requirement, which the design requirement, which makes our system the largest makes our system the largest area per station among known area per station among known GPS networks. In this way GPS networks. In this way investment efficiency is achieved.investment efficiency is achieved.
The network GPS positioning service software The network GPS positioning service software using VRS technology, using VRS technology, VRSNET, VRSNET, has achieve has achieve comparative performance through long term comparative performance through long term parallel test with Trimble GPSNet and Leica parallel test with Trimble GPSNet and Leica Spider.Spider.
During the software development, a lot of During the software development, a lot of researches are done. Such as “Modified model of researches are done. Such as “Modified model of distance correlation”, “Optimized network RTK distance correlation”, “Optimized network RTK arithmeticarithmetic”, “Modeling arithmetic for correcting ”, “Modeling arithmetic for correcting network error” and “Implementing internet real-network error” and “Implementing internet real-time service”.time service”.First VRS service software ever developed in First VRS service software ever developed in China.China.
Bring forward solutions for evaluating Bring forward solutions for evaluating network GPS positioning service using network GPS positioning service using distribution curve of uniformity of network distribution curve of uniformity of network accuracy and attenuation along the accuracy and attenuation along the distance from the network.distance from the network.
In Chengdu and Ya’an, geometry is In Chengdu and Ya’an, geometry is determined, making “Using GPS determined, making “Using GPS Technology to obtain real 3D Terrestrial Technology to obtain real 3D Terrestrial Information” a reality.Information” a reality.
Network GPS user management system is Network GPS user management system is effective and secure. Feasible for effective and secure. Feasible for commercial usage. commercial usage.
Multiple communication method for Multiple communication method for terminals. Users can select one from terminals. Users can select one from GSM/CDMA/GPRS depending their GSM/CDMA/GPRS depending their requirement and the quality of service in requirement and the quality of service in the area.the area.
The problem with different data transmit The problem with different data transmit standards is solved. Easy and reliable for standards is solved. Easy and reliable for users with different system.users with different system.
Balanced Power System is a low cost, high Balanced Power System is a low cost, high reliability power supply for man-free GPS reliability power supply for man-free GPS observation station. It solves the problem observation station. It solves the problem of lighting strike and ripple in the power of lighting strike and ripple in the power line.line.
Using the observation record, the atmosphere Using the observation record, the atmosphere water vaporwater vapor level can be determined for short- level can be determined for short-time weather forecast. time weather forecast.