Knowledge base GNSS/RTK
- FKP - A network based solution with of code and carrier using a system of gradient messages to describe the overall corrections environment (rather then corrections develop and suited to a unique position). It is in contrast to the MAC approach and has its own message types defined in RTCM.
- iMAX - A Leica term for their iMAX network which uses a nearest physical reference station approach with various network correction adjustments.
- MAC - A network based solution with of code and carrier using “Master – Axillary” methods (and messages) as defined in RTCM.
- NEAR - Implies that the users NMEA sentence will be used to select the closest physical base station and the user will be connected to that. Also called a single baseline solution.
- NRT - Another term for NEAR
- NRTK - Network RTK, a general term which can be applied to any of the terms / methods found here. As MAC and FKP methodologies have fallen out of favor, more and more solutions simply use single baseline approaches or create synthetic observations (using either legacy messages or MSM messages). NRTK is now the preferred term used for all of these.
- VRS - Virtual Reference Station, what it means is subject to debate, often involving the above terms. Of importance to many is that it may not be “virtual” at all if the term is taken to mean creating some sort of non physical reference station that is synthesized between a network of physical stations. That is of course also done, with several benefits, but use of this term does not assure you that this is so. Nor is a virtual approach of any greater value that a suitable single baseline corrections stream.
- PPP - is a signal augmentation technique that eliminates GNSS system errors to provide high accuracy positioning using only a single receiver. PPP solutions rely on GNSS satellite clock and orbit corrections which are generated from a global network of CORS. These corrections are delivered to the user via satellite or through the internet, resulting in dm-level or better real-time positioning with no local ground infrastructure requirements. PPP solutions typically require a convergence period of 5-30 min to resolve any local biases such as the atmospheric conditions, multipath and satellite geometry.