1 yard = 3 ft
1 rod, perch, or pole = 25 links = 16.5 ft
4 rods = 1 chain
1 chain = 4 rods = 66 ft = 100 links
10 chains = 1 furlong [from Marilyn Johnson]
1 link = 1/100 of surveyor's chain = 7.92 inches [note--one link of an engineer's chain = 1 ft]
25 links = 1 rod = 16.5 ft
100 links = 1 chain = 66 ft
1 furlong = 10 chains = 1/8 mile = 220 yards = 660 ft
8 furlongs = one mile (horse races are still run in furlongs if shorter than a mile)[from Marilyn Johnson]
1 mile = 80 chains = 320 rods = 1,760 yards = 5,280 ft
league = 1.5 miles (mentioned in the Doomsday book, 1067-1068)[from Marilyn Johnson], but the more modern distance used for a league is 3 statute or nautical miles.
an 'oxland' = the amount of land one ox (of a team of 8) can plough in a year [from Marilyn Johnson]
Tom Cloud has a nice page on surveying measurements and techniques at mykindred.com/cloud/TX/LandInfo/index.htm