Purpose and Summary of the Tutorial
Author: Dr Nicholas Zinas
Contact: nzinas (at) tekmon.gr
In chapter 1 the error sources that appear in the observation equations and the way they affect the GPS signals are described various error mitigation models are outlined. The linear combinations of the GPS observations between frequencies and between receivers are presented while emphasis is given to their special characteristics. The stochastic properties of the GPS observation equations are reviewed. The physical meaning of the GPS ambiguity and the ambiguity resolution and validation concepts which are essential to centimetre level positioning are discussed. Information provided in Chapter 1 are closely related and required as background reading for chapter 2.
Chapter 2 reviews the Network RTK processes. An introduction to the Differential GPS (DGPS), RTK phase positioning and the concept of the Network clusters is given. The Network RTK processes, namely a) correction generation, b) correction interpolation and c) correction transmission are reviewed in detail. The most commonly employed techniques by commercial Network RTK software suites for the transmission of the generated corrections are presented. The required message types in the standard RTCM format for data transmission are described. The chapter concludes with a discussion on the Network RTK requirements and the advances in other technological domains that enable new prospects for the further development of the field.
All the resources mentioned in the posts are referenced in the Bibliography section. Links to the referenced papers/presentations are provided where available.
The posts are open for comments, and any recommendations/additions/observations are welcomed.
2. Network RTK
To reference the GPS Network RTK tutorial use the this BibTex entry.
The limitation of single baseline real-time-kinematic (RTK) techniques is the decorelation of biases, mainly the ionospheric bias and tropospheric bias with increasing distance between reference and rover receivers. The ability to perform successful ambiguity resolution is therefore restricted by the spatial dependency of errors. Techniques that were developed to overcome this shortcoming led to the introduction of Global Positioning System (GPS) permanent tracking station networks or using an alternative terminology, GPS reference station networks. These networks consist of strategically distributed GPS receivers within a specific geographic region. GPS observation errors are approximated across a network; corrections are then generated and transmitted to the users.The purpose of these networks is to assist users operating within that region to obtain a precise position fix. The overall methodology is referred in the literature as Network RTK (NRTK).