11. All lines of longitude must be crossed. 12. They followed the line of longitude at 12?West, while Allied convoys to Gibraltar were 20?West. 13. With a latitude-longitude rectangle, only lines of longitude are great circle arcs; lines of latitude are not. 14. So does the line of longitude . 15. They travelled along the line of longitude at 12?West, while Allied convoys to Gibraltar were 20?West. 16. However, they recognize practical issues associated with the pure use of a line of longitude for this purpose. 17. On his map, the lines of longitude , instead of converging at the poles, run parallel to each other. 18. The intention was to follow the 30 degree east line of longitude , which would cover the most land. 19. If this line of longitude were used strictly, people could simply avoid Shabbat altogether by crossing the street. 20. These features made it possible to calculate changes in the time as an aviator flew across lines of longitude .
