18-Geom-B2 Satellite Navigation · December 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Paper format: National Exams, December 2014 — 3 hours, closed book (approved Casio/Sharp non-programmable calculators only). NINE questions: questions 1–7 are mandatory (80 marks) and the candidate answers one of Q8/Q9 (20 marks) for a total of 100. This is a theory paper — answers are in essay form, with two short symbolic derivations (Q2 DOP, Q4 double differencing). All nine questions, including both Q8 and Q9, are solved below for completeness.
Reference texts: Hofmann-Wellenhof, Lichtenegger & Wasle, GNSS — Global Navigation Satellite Systems (Springer, 2008); Leick, Rapoport & Tatarnikov, GPS Satellite Surveying (4th ed., Wiley); Kaplan & Hegarty, Understanding GPS/GNSS: Principles and Applications (3rd ed., Artech House); Groves, Principles of GNSS, Inertial, and Multisensor Integrated Navigation Systems (2nd ed., Artech House) for Q9; Natural Resources Canada — Canadian Geodetic Survey (CSRS-PPP service, Canadian Active Control System). Canadian frame throughout (NAD83(CSRS), NRCan reference products).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Global Navigation Satellite Systems (GNSS) fall into two tiers: global constellations designed to give worldwide coverage from a full complement of satellites (nominally 24 or more in Medium Earth Orbit), and regional systems and space-based augmentation systems (SBAS) that serve a limited service area. At the time of this examination two global systems are fully operational, two more are in active deployment, and several regional systems are being built.
Fully operational global systems. GPS (NAVSTAR), operated by the United States, has been at Full Operational Capability since 1995 with a nominal 24-satellite (currently 31-satellite) constellation in six orbital planes at ~20 200 km; it is the reference against which the others interoperate. GLONASS, operated by the Russian Federation, returned to a full 24-satellite constellation in 2011 after restoration through the 2000s, and provides global coverage using FDMA signals (with CDMA signals being added). These are the only two constellations that are, on their own, globally complete and continuously usable.
Global systems under development. Galileo, the European Union’s civil-controlled system, is in deployment: its In-Orbit Validation phase is complete and satellites are being launched toward the 30-satellite constellation, with Initial and Full Operational Capability following later this decade. BeiDou (Compass), operated by China, is operational regionally over the Asia-Pacific from its BeiDou-2 phase and is expanding to a global (BeiDou-3) constellation. Both are being designed to be interoperable with GPS on common frequency bands (e.g. Galileo E1/GPS L1).
Regional systems and augmentation. QZSS (Japan) uses highly-inclined, quasi-zenith orbits to improve coverage in urban canyons over Japan and is GPS-interoperable. IRNSS/NavIC (India) is a regional constellation of geostationary and geosynchronous satellites serving the Indian subcontinent. Overlaid on all of these are the SBAS: WAAS (North America), EGNOS (Europe), MSAS (Japan) and GAGAN (India), which broadcast wide-area differential corrections and integrity data from geostationary satellites. For Canadian users, GPS+GLONASS presently provides the operational multi-constellation backbone, with WAAS augmentation available nationwide.
