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Reference Station Applications Reference Station Networks: A Conceptual Study using their Information with the Current and Next Generation RTCM Messages
| Content Provider | Semantic Scholar |
|---|---|
| Author | Euler, Hans-Jürgen Dr.-Ing. Keenan, Ryan Zebhauser, B. E. Wübbena, Gerhard Euler, H.-J. Keenan, Craig R. |
| Copyright Year | 2002 |
| Abstract | In applications requiring centimeter accuracy, single baseline positioning methods are being superseded by those methods using information from permanent reference station networks. The well known advantages afforded by reference station arrays include improved modeling of the remaining tropospheric, ionospheric and orbit biases. Methods and concepts show the improvements in performance and reliability in some kind of closed system approaches. Standardization discussions underway within RTCM target the interoperability between the reference station systems and roving receivers from various manufacturers. One obstacle in the discussion, and therefore in later interoperability issues, is the creation and proper description of the models used for deriving the biases noted above. This difficulty has to be mitigated and will vanish with time, but this interoperability is needed urgently. This paper details a different approach to utilize and distribute the information from permanent reference station networks in RTCM Version 3.0 compatible message types. Throughput calculations show their efficiency. The separation of different calculation tasks demands an easy, powerful and broadcast sufficient standard for the transfer and distribution of network information. The method proposed here does not restrict roving users to one specific network positioning concept, yet provides the opportunity for applying simple interpolation methods. Such a concept may solve the current dilemma concerning interoperability standards. INTRODUCTION / MOTIVATION Real-time messages for proper interoperability between different manufacturers’ equipment have been issued by the RTCM Sub-Committee 104 (RTCM, 2001). All information for precise positioning using baseline approaches can be transmitted using Version 2 message Types 18-21 or in the future using Version 3 message Types 101 and 103 respectively. Because the use of single reference stations has some disadvantages in that the accuracy and reliability of integer ambiguity resolution deteriorates with distance from the reference station, networks of reference stations are being developed to mitigate the distance-dependency of RTK solutions. With such networks, a provider can generate measurement corrections for receivers operating within the network area and can supply this information to the user in a standardised format. As the current kinematic and high-accuracy message types do not support the use of data from multiple reference stations, new standards must therefore be considered to facilitate the valuable information afforded by reference station networks. The standardisation of network information and processing models is also necessary to reduce the sizes of the network RTK corrections, as well as the transmission of satellite-independent error information. A simplified approach of transmitting data from reference station networks to roving users is now presented in this paper in the form of a new message standard capable of supporting reference network operations. Its use should help overcome some of the problems encountered in current network RTK concepts. For a short summary of the existing concepts “FKP” and “VRS” including a discussion of problems we refer to EULER et al. (2001). Specialised models requiring detailed description and discussion are not used in this proposal. FUTURE V3.0 EVOLUTION The future Version 3 of RTCM DGNSS messages (RTCM V3.0 DRAFT, 2001) differ from those of Version 2.3 in terms of increased flexibility and efficiency. This is promoted by a layer approach consisting of application, presentation, transport, data link and physical layer. In this paper we focus only on the presentation layer that describes the message formats and how to apply them. For a throughput analysis one has also to consider the transport layer. With this higher efficiency was achieved by replacing the 20% parity bits overhead per word with one Cyclic Redundancy Check at the end of the whole message. One message can reach 32767 bytes in length and always fits the byte boundary. A short preamble and length definition replaces the 2 words (60 bits) message header of Version 2.3. A short or long message type can be chosen, which differ in the message overhead of 40 against 48 bits in total. The message numbers start with |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://w3.leica-geosystems.com/downloads123/zz/general/general/tech_paper/Leica_Technical_Report%20-%20GNSS2002_en.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
