| ID | Author | Article | Link | Source | Date | Page |
|---|---|---|---|---|---|---|
| 1169 | Derek Pilgrim | Before GPS part 1 – the Wayfinders Historical perspective on how navigation was done before electronic navigation |
link | Page: 19 | ||
| 1229 | Derek Pilgrim | Before GPS, part 2, The Measurers Early compasses, logs, sounding lines, and equipment for measuring celestial elevation |
link | Page: 21 | ||
| 1293 | Derek Pilgrim | Before GPS, Part 3 Continued series on history of navigation |
link | Page: 31 | ||
| 1327 | Derek Pilgrim | Before GPS Part 4 Continuation of series - Radio Aids to Navigation |
link | Page: 31 |