How tall is the ladder?

Solution 1:

According to user DrkAndStormy on Reddit, it's about 412 feet (125 meters) high:

After looking closely at footage and playing it back and what not, it turns out Naked Snake makes his way up 3 bars in a single second. The entire climb takes 1 minute and 47 seconds. After a bit of math, you'll find Snake climbed a total of 321 bars. If Naked Snake is 6'5", then that means he is roughly the height of 5 bars on the ladder. With the knowledge that there are 321 bars, and each 5 bars are roughly 77 inches tall, we can say Naked Snake climbed 411.95 feet worth of ladder.

That's assuming a lot of variables, but seems to be a decent estimate.

Also this.

Solution 2:

In the video we can see the following: 306 steps were climbed, going by sound. Standing, Snake is 4,5 steps high. Snake is 1,92m tall according to canon. So... 306/4.5 = 68 Snakes. 68*1,92 = 130,56m. Accounting for errors, we'll round up, so roughly, the ladder is 131m, or 430ft.