Special Feature

Multi-Constellation GNSS/RNSS From the Perspective of High Accuracy Users in Australia

C. Rizos

School of Surveying & Spatial Information Systems

University of New South Wales

Sydney, NSW 2052, AUSTRALIA

c.rizos@unsw.edu.au

Abstract

Global Navigation Satellite Systems (GNSSs) involve satellites, ground stations and user equipment, and are now used to support many activities within modern societies. The U.S. Global Positioning System (GPS) is the best known, and only currently fully operational GNSS. Russia also operates its own (not yet fully deployed) GNSS called GLONASS. Fuelling growth in applications during the next decade will be next generation GNSSs that are currently being developed and deployed. Next generation GNSSs will include the U.S.’s modernized GPS and planned GPS-III, Russia’s revitalised GLONASS, Europe’s GALILEO system, and China’s planned COMPASS system. Furthermore, a number of Space Based Augmentation Systems (SBASs) and Regional Navigation Satellite Systems (RNSSs) will add extra satellites and signals to the multi-constellation GNSS/RNSS ‘mix’. How will this proliferation of satellites and signals impact on the spatial information disciplines? Is the concept of a ‘system of systems’ receiver, and associated ground infrastructure, to support high accuracy positioning feasible, or even desirable? This paper explores some of the issues of multi-constellation GNSS/RNSS from the perspective of high accuracy users such as geodesists, surveyors and mappers, in Australia.

New Geodetic Infrastructure for Australia

P. Tregoning

The University component of the AuScope Geospatial Team

Paul.Tregoning@anu.edu.au

Abstract

In November 2006, the Australian Federal Government announced $15.8M in funding for geospatial research infrastructure through the National Collaborative Research Infrastructure Strategy (NCRIS).  NCRIS is an initiative under the Australian Government’s Backing Australia’s Ability package with a number of key principles, including maximising the contributions of the R&D system to economic development, national security, social wellbeing and environmental sustainability.  Here we outline why particular components of geospatial infrastructure are required in Australia to advance (equip) geospatial research over the next 20 years.  We describe some of the scientific objectives that required an upgrade and densification of Australia’s geospatial infrastructure.  This paper is the perspective of researchers from a subset of University researchers involved in the AuScope Geospatial component, and so does not necessarily encompass the opinions of all those involved in AuScope geospatial.

 An Organisational Model for a Unified GNSS Reference Station Network for Australia

M. B. Higgins

Principal Survey Advisor

Department of Natural Resources and Water

Locked Bag 40

Coorparoo DC Qld 4151

and

Cooperative Research Centre for Spatial Information

733 Swanston St

Carlton Vic 3053

Australia

matt.higgins@qld.gov.au

Abstract

In Australia, there are many reference stations gathering data from Global Navigation Satellite Systems (GNSS). These so-called GNSS reference stations are being used to enable precise positioning in support of applications across many industries. However, the lack of coverage in sparsely populated regional areas is affecting the realisation of the opportunities offered by precise positioning to key industries, such as agriculture and mining. Given that it is difficult for single organisations to justify covering large areas of regional Australia, there is a need for partnership models to support a unified GNSS reference station network for Australia.

This paper begins by describing precise positioning using GNSS and differentiates between post processed and real time applications. Commercially available techniques for delivering real time precise positioning services are reviewed, including the Virtual Reference Station approach, the Master Auxiliary Concept and precise point positioning in real time mode (referred to as PPP-RTK). The paper then goes on to describe the current situation with precise GNSS positioning networks in Australia and the problems of delivering real time services in sparsely populated regional areas. The key contribution of the paper is to propose a model to identify and discuss the roles played by organisations delivering precise positioning services. The paper concludes by outlining how such a model might be applied in order to understand the differing organisational roles required for the development and operation of a unified GNSS reference station network for Australia.

GPSnet CORS Network Management Validation Through User Feedback

M. Hale

P. Collier

A. Kealy

CRC for Spatial Information and Department of Geomatics

The University of Melbourne

Parkville, Victoria

m.hale@pgrad.unimelb.edu.au

p.collier@unimelb.edu.au

a.kealy@unimelb.edu.au

Abstract

Australian state sponsored RTK CORS networks cover limited areas, operate in isolation and lack consistent management. This has resulted from the independent and largely uncoordinated efforts of state and territory governments to establish and manage RTK CORS networks. This study investigated CORS network management in relation to institutional, legal, commercial and operational requirements. Responses to two questionnaires, one directed to Victoria’s GPSnet users and another made available in Australia and internationally, were analysed. The study found user satisfaction with Victoria’s GPSnet management arrangements, indicating their potential to underpin a nationally consistent approach to CORS network management in other jurisdictions.

 GNSS-based Heighting in Australia:  Current, Emerging and Future Issues

W.E. Featherstone

Western Australian Centre for Geodesy

& The Institute for Geoscience Research,

Curtin University of Technology,

GPO Box U1987, Perth WA 6845

W.Featherstone@curtin.edu.au

Abstract

Ellipsoidal heights, i.e., w.r.t. a geometrical Earth figure, determined from Global Navigation Satellite Systems (GNSS) are inherently their least accurate coordinate, due mainly to satellite geometry and atmospheric refraction.  For most practical purposes, however, these GNSS-derived ellipsoidal heights have to be transformed to heights that relate to the Earth’s gravity field, which generally adds further uncertainty.  The reduction in accuracy of the transformed height is due to errors in gravimetric quasi/geoid models, but this is compounded yet further in Australia – and elsewhere – because of the imperfect realisation of local vertical datums.  This paper comments upon current, emerging and future issues with height determination on the Australian Height Datum (AHD) using GNSS.  This comprises the reference frame used for GNSS ellipsoidal heights, theory- and data-driven inaccuracies in modelling the quasi/geoid, and deficiencies in the realisation of the AHD.  While some of these issues will be redressed, in part, by the production of AUSGeoid2008 that is fitted to the AHD, there will always be the need to routinely apply checks on GNSS-derived heights in Australia, and elsewhere. 

 A Benefit of Multiple Carrier GNSS Signals: Regional Scale Network-Based RTK with Doubled Inter-Station Distances

Y. Feng

B. Li*

Faculty of Information Technology

Queensland University of Technology, GPO Box 2434, QLD 4001, Australia

and

Cooperative Research Centre for Spatial Information

723 Swanston Street, Carlton, Victoria, 3053, Australia

* also Department of Surveying and Geo-informatics Engineering

Tongji University, Shanghai 200092, P.R. China

y.feng@qut.edu.au

Abstract

This paper presents a regional scale network-based real time kinematic positioning strategy based on the use of three carrier GNSS signals, in which the inter-station distances of the network could be doubled, that is, around 140 to 180 km instead of the current 70 to 90 km with the use of dual-frequency GPS receivers. The paper outlines the most efficient virtual observables and models that allow for resolving ambiguities of three carriers with observation of above 7 minutes for baselines of a few hundreds of kilometres. As a result, the remaining key limiting factor for implementation of the regional scale network RTK is the distance-dependent residual tropospheric bias. A reference station placement scheme of doubling the inter-station distances is then suggested based on the interpolation accuracy of the tropospheric errors within the network. A semi-simulation procedure is introduced for generation of the third GPS signal from the real GPS L1 and L2 data to allow for more realistic assessment of TCAR performance benefits in real world situations. Numerical studies performed with 24-h data sets from four US CORS stations have demonstrated the superior AR performance benefits of the outlined TCAR algorithms, providing the technical basis for the deployment of regional scale network RTK services with doubled inter-station distances. The distance-independent nature of the AR performance has significant implications for future GNSS technological evolutions and applications.

Assessing and Reporting Real-Time Data Quality

for GNSS Reference Stations

S. Fuller

P. Collier

J. Seager

Cooperative Research Centre for Spatial Information

723 Swanston Street, Carlton, Victoria, 3053

simon@geomatix.com.au

Abstract

Real-time positioning, based on CORS network technology, is becoming a routine operation within and outside the spatial industry.  The expanding user base and diverse range of applications employing this technology can impose significant expectations on the providers of network RTK services.  As a consequence, there is a pressing need to supply network operators with dependable, real-time information regarding data quality.  This paper addresses the question of how to assess the real-time performance of CORS stations by means of comparison against a historical data archive, along with a discussion on intelligent alerting of network operators when noteworthy quality breaches occur.

Professional paper

 Remote Sensing, Spatial Multi Criteria Evaluation (SMCE) and   Analytical Hierarchy Process (AHP) in Optimal Cropping Pattern Planning for a Flood Prone Area

Md. Rejaur Rahman

Department of Geography and Environmental Studies,

University of Rajshahi,

Rajshahi-6205, Bangladesh.

rejaur2001@yahoo.com

S. K. Saha

Agriculture and Soils Division,

Indian Institute of Remote Sensing (IIRS), NRSA,

Dehradun, India

Abstract

A GIS-aided multi-criteria evaluation (MCE) approach in land suitability analysis for crops was described in this study and used to suggest suitable cropping patterns for a flood prone area, the Bogra district of Bangladesh. The major objective of this study was to suggest an optimal cropping pattern to combat adverse effects of flood using integrated analysis of land suitability for crops derived by spatial multi-criteria evaluation (SMCE) and the analytical hierarchy process (AHP). For land suitability analysis, Rice (Aman), Mustard, Potato and Wheat crops, which were prominent in the study area, were selected for this study. IRSP6: LISS III satellite data was used to generate flood and post flood land use/land cover maps of the area. To classify the satellite data, an object-oriented digital classification procedure was performed.  To generate the necessary factors and constraints for the SMCE approach, remote sensing and GIS integrated techniques and models were applied. To standardize all of the factors for the MCE, the AHP method was used. The results of the suitability analysis depicted that in the study area, the land was highly to moderately suitable for the crops. Due to the flood hazard in the flood season (Kharif), some areas were found marginally suitable for Rice (Aman). Optimal cropping patterns for the flood and post flood season based on crop suitability and expert knowledge indicated that the Rice-Wheat/Potato, Rice (Late sowing)-Potato, Rice-Potato and Rice-Mustard combinations were found the most suitable suggested pattern for the study area.