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.
GPS modernization is the multi-decade program by which the United States is upgrading all three GPS segments — space, control and user — to add new civil and military signals, improve accuracy, integrity and robustness, and make GPS interoperable with the other GNSS. It is being implemented gradually as new satellite blocks replace ageing ones.
New civil signals. Three new civil signals are being added to the original L1 C/A. L2C, a second civil signal on the L2 frequency, first appeared on the Block IIR-M satellites; having two civil frequencies lets an ordinary user form the ionosphere-free combination and remove the largest error source without a military-code receiver. L5, broadcast on a protected aeronautical radionavigation band, arrived with Block IIF; it is a high-power, wideband “safety-of-life” signal for aviation. L1C, arriving with Block III, is designed to be interoperable and compatible with Galileo E1 and other GNSS on the common L1 band.
New military signals. A new military M-code is added on both L1 and L2 (from Block IIR-M onward). It is spectrally separated from the civil signals, more resistant to jamming and spoofing, supports higher-power “spot-beam” transmission over theatres of operation, and allows autonomous security key handling.
Satellite and control segments. The signals are delivered by successive satellite generations — Block IIR-M (L2C, M-code), Block IIF (L5), and Block III/IIIF (L1C, higher power, laser retroreflectors, longer design life). The control segment is being upgraded through the Next-Generation Operational Control System (OCX) and an expanded network of monitor stations, giving better orbit and clock determination, faster uploads and improved integrity monitoring.
Benefits. Collectively, modernization gives civil users dual- and triple-frequency ionospheric correction, better accuracy and availability, greater resistance to interference, and cross-compatibility with Galileo, GLONASS and BeiDou — the foundation of today’s multi-frequency, multi-constellation receivers used in Canadian surveying.
