CORS network provide by PT Zi-Techasia, using a high precision antenna for all present and future GNSS signal, a Receiver from NavXperience GmbH, Germany (www.navxperience.com ) and GNSMART software from GEO++ GmbH, Germany. (www.geopp.de/products/reference-stations/), the old recompany . GNSS-SMART comprises the monitoring of the state of the whole system including regional atmospheric effects, together with its presentation and delivery to the user for the purpose of position determination with the highest accuracy, reliability and availability, both in real-time and by post-processing.
Geo++ has an excellent expertise in GNSS antenna and station calibration. This included the development of unique field experiment and measurement facilities for GNSS, which initiated broad scientific investigations and changes in modeling worldwide. The robot-based calibration system has been successfully realized in several collaborative research and funded research projects with the Institut für Erdmessung, Leibniz Universität Hannover.
The role of the GNSS site impact on GNSS performance is generally underestimated. The robot-based calibration system allowed for the first time to determine the effect of near-field reflectors on GNSS antennas. Today, it is commonly accepted to distinguish between antenna phase variations, near-field effects and far-field multipath. Geo++ researches documented the impact of unfavorable site setups (antenna and mounting) causing significant degradation of GNSS network rover performance. New technologies to enable operational station calibrations are under investigation at Geo++.
Such unfavorable station setups can be best avoided already in the phase of station selection and setup. Only in some limited cases corrections for the near-field effects can be determined. Geo++ experiences may help to decide on proper GNSS sites.
is the basic version, which is capable to process most GNSS applications for small, medium or large and worldwide baselines or networks.
is in addition able to determine kinematic trajectories in any interval.bFor special purposes (e.g. antenna calibration, attitude determination, deformation analysis) some extensions are available as additional GNNET options.
Compared to common post-processing programs GNNET- POST has some remarkable features:
- rigorous multi-station, multi-session network adjustment
- simultaneous adjustment of multiple reference
stations and multiple mobile receivers, max. number of station and sessions depends only on computer capacity
- use of non-differenced observations, therefore no loss of correlations between observations
- use of code and carrier phase observations
- automated, integrated use of various linear combinations of dual frequency observations
- receiver independent through use of a RINEX interface
- use of precise ephemeris (if available)
- use of GPS and GLONASS observations
- simultaneous processing of single and dual frequency observations
- dynamic modelling of atmospheric parameters (troposphere, ionosphere)
- optimized ambiguity resolution, allows solutions with very short observation times
- simultaneous L1 and L2 ambiguity resolution, allows fast and automatic ambiguity determination in a single run
- evaluation of all common observation techniques:
- Rapid Static,
- Pseudo-Kinematic (re-occupation),
- Stop and Go,
- kinematic trajectory (only with GEONAP- K)
- ambiguity resolution Real-Time-Kinematic, On
the Way, On the Fly, On the Track
- 3-D trajectory determination with 1cm-accuracy or better
- Parameter estimation
- station coordinates (absolute, relative), incl. full covariance matrix
- satellite orbit parameters using kinematic orbit improvement
- receiver and satellite clock parameters
- atmospheric parameters (ionosphere, troposphere), functional and stochastic
- carrier phase ambiguities
- biases (hardware biases, tracking biases, signal biases, code-phase biases, …)
- 2-D or 3-D attitude determination from antenna array (optional)
- GNSS network adjustment to connect sessions and include external observations
GNSMART is based on the procedures known as GNSS- SMART (Global Navigation Satellite System – State Monitoring And Representation Technique).
With any GNSS (currently GPS or GLONASS), high resolution observations are made, but in practice these are still affected by numerous sources of error (satellite orbit errors, ionospheric and tropospheric effects). The complete system including its error sources can always be considered to be in a dynamic state. GNSS-SMART comprises the monitoring of the state of the whole system including regional atmospheric effects, together with its presentation and delivery to the user for the purpose of position determination with the highest accuracy, reliability and availability, both in real-time and by post-processing.
From the user’s point of view, in contrast to conventional procedures, no knowledge of the internal structure of the GNSMART system is necessary. By means of the reference data supplied by GNSMART, the user receives observations free of systematic errors, which enable him to determine absolute positions with a homogeneous and high standard of accuracy using a single mobile instrument. Thus it is possible for the first time to make very accurate measurements in relation to a high order reference frame without local connecting observations.
Typically, the maximum distance between a base station and rover GNSS set up is around 10-15 km. This is due to the effect of the atmosphere on the GNSS signals as they travel from the satellite to a GNSS receiver.
With the establishment of a network of CORS, the distance between the base and the rover can be extended. The CORS can be spaced around 150 km apart and using at least 3 of these CORS, the atmospheric effects can be modeled and corrected for, yielding the ±20 mm position.