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Welkom bij de Trimble Pivot Web applicatie!
Global Navigation Satellite Systems (GNSS) has revolutionized our ability to access location information. In nutshell it measures its distances from a bunch of satellites hovering over the earth in predefined orbits, through radio signals and estimates its own position on earth. However, this system has its own share of error budget due to Orbit errors, Satellite Clock error, Receiver noise, Ionospheric and Tropospheric delays, Satellite Geometry over receiver and multipath etc, which causes dilution in its precision up to 10 -11 meters. To overcome this accuracy limit, various Surveying techniques such as DGNSS, Static GPS/GNSS surveying, RTK, SBAS, GBAS, and PPP are being used by Geospatial community. Each of these method works own principal of taking GNSS measurement. In most of GNSS applications where precise positioning is required, users usually pair their GNSS instruments with other GNSS instruments, simultaneously observing one or more known position, termed as reference station, and with help of these reference stations estimated corrections to be applied over point of interest or rover position are obtained through Static GNSS Survey or Real Time-Kinematic (RTK) Survey methods.
To liberate users from setting of their own reference station each time they wish to undertake GNSS measurement, the directorate of geographic affairs has established a network of Continuously Operating Reference Stations (CORS), which not only capable of providing Real Time Positioning Service through RTK/NRTK with an accuracy of ±3cm, but also host an array of different positioning services targeted to cater requirements for different segments of Geospatial and scientific Community.
At present CORS Network covers all the territories on which there is internet.
CORS infrastructure is basically a Network of permanently installed reference stations (or GNSS receivers), continuously streaming raw satellite observations to a central server. The Central sever archive and catalogue these reference station data, analyses and process it for further consumption which will be used by users. The entire setup of Reference Stations and Central Server is known as Continuous Operating Reference Station (CORS) Network.
The CORS network (13 stations) is available 24 hours per day, 7 days a week and 365 days a year.
1. Network RTK Services for 3 – 4-centimeter real time positioning.
Real-Time Kinematic (RTK) is a widely accepted technology for accurate positioning and navigation. This method is an extension of Single base RTK survey technique in which, a GNSS rover connecting to a single base or reference station with known coordinates. This survey technique gives centimeter level positioning accuracy. However, by Networking several such reference station range, accuracy as well as reliability of RTK survey technique can be improved multifold. The central server collects all raw observations of these reference stations in real time and runs specialized software, which uses satellite observations of reference stations and performs calculations to create a model of spatially correlated bias and their pattern of change over the whole area. These correction models are made available to users via internet so that GNSS instrument of user can derive bias for its position and refine its position to get centimeter level accuracy in near real time. For utilizing this real time services, user will be required RTK enabled GNSS equipment, a controller unit with RTK field survey software and access to internet via wifi, 4G/5G mobile phone modem or any other mean.
2. Data processing of static observation with respect of CORS.
At present, for GNSS measurements, users need to pair their GNSS instruments to other GNSS instruments, simultaneously observing one or more Master Stations (Station whose coordinates are known). Duration of observation in these cases increases with respect to distance between Master and Rover stations.
With CORS in place, there is NO need to use paired GNSS equipments. Using single GNSS equipment, control points with respect to National Reference frame can be established with much lesser observation period and better reliability and consistency in Survey work. User can put his GNSS rover, on his point of interest, collect data in static survey mode and upload his data in RINEX format into processing platform. Processing platform will process data and provide coordinates of site along with processing report.
3. Downloading of RAW Data of CORS Stations for processing in user software.
For more precise or scientific applications users can download CORS stations raw observations in nonproprietary open RINEX format or virtual rinex data (i.e. RINEX files for a virtual reference station that can then be used for post processing calculations), and use it to process his own GNSS data it his own software. These data can also be used to track earth’s crustal movements and other Earth science related studies.
The user can create custom orders; individual stations or multiple stations, epochs, time periods, and various formats such as Rinex2.1, Rinex 2.11, Rinex 3, T02, TGD, DAT, T01 or VRS Rinex and various logging rate 1 minute, 15 seconds, 1Hz, 5Hz, 10Hz, 15Hz, 30Hz...etc.
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