I find it fascinating that people get so freaked out about ditches being more than 3 feet wide, when a normal canter stride on a normal sized horse is 12 feet long.
There is a common misconception that a jump is “just a long canter stride” or that jumping a ditch is “just a long canter stride”. One mistake is thinking that the jump happens during the regular suspension phase of the canter stride. However, jumping anything, even a ditch, is not “just a long canter stride”. The footfall of a jump and moment of suspension of the jump within the footfalls are both totally different from the footfalls and moment of suspension in a canter stride.
In a normal left lead canter stride, the horse lands with the right hind foot first, then about 3 feet further the left hind lands, with the right fore landing in tandem about 3 feet ahead of that, then about 3 feet after the right fore touches down, the left fore (leading leg) lands (about 9 feet ahead of the right hind) which happens after the right hind has already broken over and begun flight forward. During the moment of suspension the right hind comes forward and lands about 3 feet ahead of the left fore (about 12 feet forward of the previous landing) but at no point in the stride is there a “12 foot gap” between the group of footfalls.
You can test/prove this to yourself by cantering your horse on a freshly dragged area of the ring, then get off and examine the hoof prints. The takeoff point of the jump is where the front feet land at the end of a canter stride, but the horse doesn’t just lift up the feet and clear the jump, commencing with a normal canter stride (starting with a hind hoof) on the other side. Instead, the horse changes the stride to produce the 4 footfalls of the jumping effort.
As the horse approaches the takeoff to a jump (at the end of the last full canter stride) the horse pushes off, pushes up with the front legs (only!) as they end the last regular stride, lifting the shoulders up to the angle for the take-off of the jumping stride. Then the hind legs are brought up to the same spot where the front legs were (not passing the front legs as happens during suspension in a regular canter stride), with the hind hoofs landing in the same spot (the “take-off spot”) as the front hoofs. Then the horse pushes up from the hind legs to further propel the horse’s body over the jump. On landing, the horse lands front legs first, landing and pushing up again (patting down and back up), bringing one (if not both) of the front legs into the air before the hind legs land. As the hind legs land the horse commences the first post-jump canter stride although the sequence will often be a 4-beat stride as the first-to-land front leg is often still in flight and can’t land in tandem with the partner hind leg. The beginning of the jump starts with the front legs pushing off at the end of the previous stride. Then the footfall of the jumping “stride” is hind, hind, suspension, front, front – with a jump/suspension phase in an entirely different point in the hoof-falls from the regular canter stride of hind, hind/front, front, suspension.
For more info, see:
Muybridge – Jumping horse animated gif 
Muybridge – Jumping horse animated jpeg