WHOA. CANADA! July 1 marks Canada's sesquicentennial. In 1867, Ontario, Quebec, Nova Scotia and New Brunswick joined to form The Dominion of Canada. Other provinces came on board later with the last, Newfoundland and Labrador, joining in 1949. Apart from my interest in educating all and sundry about the origins of the "true north, strong and free," what has this got to do with GNSS? Well, it turns out that Canada has played and continues to play an important role in the development of communications and navigation technologies. Robust PNT services from LEO are here today, providing augmentation to GPS where GPS isn't available. The addition of navigation signals from LEO provides a number of benefits. The faster LEO motion provides geometric diversity, giving rise to multipath whitening, faster initialization times for carrier-phase differential GNSS, and Doppler-based positioning. Perhaps most importantly, LEO constellations have the advantage of being closer to the Earth than the GNSS core constellations in MEO, experiencing less path loss and delivering signals 1,000 times (30-dB) stronger. This makes them more resilient to jamming and more capable in deep attenuation environments such as in urban canyons and indoors. This extra power allows the LEO-based Satelles STL using Iridium to achieve timekeeping within 1 microsecond and a positioning accuracy of 20 meters, all while deep indoors where GNSS is unavailable. This adds indispensable resilience and security to GNSS that we are increasingly reliant upon, creating a comprehensive satellite navigation system that truly works everywhere.
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