Global Navigation Satellite Systems GNSS Accuracy 10 m

Global Navigation Satellite Systems GNSS Accuracy 10 m or better Galileo EU/ESA GPS USA Planned India, Japan, Korea GLONASS Russia Compass China

Space Based Augmentation Systems Improves GNSS accuracy to 3 metres

GNSS Errors Ionospheric & Tropospheric diffraction 10 + 1 metres Canyon Effect – 1 metre Part copied from http: //www. kowoma. de/en/gps/errors. htm Geometry up to 100 m Timimg errors 4 m – Rounding errors 1 m Orbits up to 5 m

Ionospheric effects ± 5 metres Shifts in the satellite orbits ± 2. 5 metres Clock errors of the satellites' clocks ± 2 metres Multipath effect ± 1 metre Tropospheric effects ± 0. 5 metre Calculation & rounding errors ± 1 metre All adds up to +- 15 m – 10 m typically stated With EGNOS still +-3 to 5 m according to this source However +- 1 m considered realistic

R 1 Ephemeris – Actual Position of the Satellite Time – determines how far away we are R 1 Geometry locates us anywhere on the surface of a sphere

R 2 R 1 Ephemeris – Actual Position of the Satellite Time – determines how far away we are R 1 Geometry locates us anywhere on the surface of a sphere Intersect 2 Spheres gives a ring

R 2 R 1 R 3 Ephemeris – Actual Position of the Satellite Time – determines how far away we are R 1 Geometry locates us anywhere on the surface of a sphere Intersect 2 Spheres gives a ring Intersect 3 Spheres gives 2 points 4 spheres gives a 3 D position

CODE DIVISION MULITPLE ACCESS – CDMA SPREAD SPECTRUM GNSS DATA + TRANSMISSION SPREADING CODE CORRELATOR DATA OR PRN RECEPTION

http: //www. novatel. com/an-introduction-to-gnss/chapter-1 -gnss-overview/ http: //www. navipedia. net/

http: //www. ni. com/whitepaper/7139/en/#toc 1

http: //www. nbmg. unr. edu/Staff/pdfs/Blewitt%20 Basics%20 of%20 GPS. pd f

Coarse Acquistion 1023 bits, 1. 023 MHz = 1 ms repetition rate Precise Code 6. 1871 × 1012 bits long (6, 187, 100, 000 bits) Part of 2. 35 × 1014 bits in length (235, 000, 000 bits) 10. 23 MHz May be modulates with a W-code to prevetn Spoofing Navigation Message 50 BPS – Date & Time – Ephmeris – Almanac 1500 Bit frame in 5 sub-frames of 300 bits - each takes 6 seconds to arrive

Cold Start – Load The Almanac – where are the satellites Warm start – get satellite data and extract Ephemeris (position) and time Calculate UTC Do Geometry and get a 3 D fix Use SBAS to correct Fix Use Regression to get better accuracy ASSISTED GPS – this is a technique whereby another source of location data is used to enable the device to start seeking the most apprpriate satellites. E. G. CELL-ID, dead reckoning or just memeory

Space Based Augmentation Systems Improves GNSS accuracy to 3 metres

INTRODUCTION TO DATA OVER GSM ANALOGUE – e. g V 22 etc SHORT MESSAGE SERVICE – SMS GPRS BASIC SMS COMMANDS AT+CMGS=”+447967123456” > ENTER TEXT CONTROL Z AT+CMGR=NN AT+CMGD=NN AT+CMGW=”+44796123456” > ENTER TEXT CONTROL Z AT+CMSS = NN