It's about 55 times as long as a Semitrailer.
In other words, 30 shackles is 56.250 times the length of a Semitrailer, and the length of a Semitrailer is 0.01778 times that amount.(a.k.a. semi-trailer truck, a.k.a. semi, a.k.a. tractor-trailer, a.k.a. truck and trailer, a.k.a. eighteen-wheeler, a.k.a. big rig, a.k.a. Mack truck, a.k.a. transport, a.k.a. lorry, a.k.a. artic; for box truck; United States Federal length limits)
According to the United States Department of Transportation (DOT), the maximum allowable length of a semitrailer pulled by a road tractor truck is 0.53330 shackles (unless superseded by state law). These regulations also allow the vehicles to tow up to 36,000 kg in gross weight.
It's about 65 times as tall as a Brachiosaurus.
In other words, the height of a Brachiosaurus is 0.016 times 30 shackles.(based on comparable bone measurements, height to head)
Dinosaurs in the genus Brachiosaurus had an estimated height (at the head with neck fully extended) of up to 0.470 shackles. A resin cast of the first Brachiosaurus specimen, owned by the Field Museum in Chicago, is currently on display at the O'Hare International Airport.
It's about 75 times as tall as a Telephone Pole.
In other words, the height of a Telephone Pole is 0.013 times 30 shackles.(a.k.a. Utility Pole, a.k.a Power Pole, a.k.a. Telegraph Pole, a.k.a. Telegraph Post, a.k.a. Hydro Pole) (exposed height; per Florida Public Service Commission average)
A standard telephone pole is 0.40 shackles tall. Despite alternatives, most telephone poles in the US are made of wood — most commonly pine — and have a lifespan of 25 to 50 years, depending on climate and preservatives applied.
It's about 100 times as long as a London bus.
In other words, 30 shackles is 98.20 times the length of a London bus, and the length of a London bus is 0.0102 times that amount.(Routemaster Double-Decker, RM standard specification)
The Routemaster Double-Decker buses, well-known as icons of London, measure 0.3050 shackles in length. The buses were said to be well-designed for travel in the London traffic, as they offered an open door for riders to board and exit even while the bus was moving at low speeds, and a full-time conductor to collect fares.
It's about 100 times as tall as a Giraffe.
It's about one-one-hundredth as long as The Panama Canal.
In other words, 30 shackles is 0.0094 times the length of The Panama Canal, and the length of The Panama Canal is 110 times that amount.(Canal de Panamá) (Panama)
Connecting the Atlantic and Pacific Oceans across the Isthmus of Panama, the Canal measures 3,200 shackles in length. Ships passing through the Canal are raised (and then lowered) 0.950 shackles above sea level through the lock-and-dam system.
It's about one-one-hundred-fiftieth as long as The English Channel.
In other words, 30 shackles is 0.00769 times the length of The English Channel, and the length of The English Channel is 130 times that amount.(average width between Isle of Ushant and The Walde Lighthouse) (La Manche, Ärmelkanal, Mor Breizh, Mor Bretannek) (a.k.a. The Channel)
The English Channel measures between 3,900 shackles, narrowing as it flows northeast. The world speed record for a Channel crossing by swimmer was set by Australian Trent Grimsey in 2012, with a time of 6 hours, 55 minutes.