Sam Rutherford kindly dug out this article
http://www.condoraudio.com/wp-content/uploads/Highlights/1985ParisRally.pdf
…and has it posted on the page for the 2019 rally.
What was interesting that the crew had to resort to solar navigation when the Loran signal became unusable.
GPS accuracy can also be degraded at high latitudes due to solar radiation and the location of satellites (although Glonass apparently is better).
Worth thinking what back up navigation plan you would use if the GPS packed up.
