We can see a right triangle here.
Diagonal is a hypotenuse of the right triangle. Two legs are equal 102 yards each.
We can use Pythagorean theorem
hypotenuse² = leg² + leg² = 2leg²
hypotenuse² = 2leg²
√hypotenuse² = √(2leg²)
hypotenuse = leg*√2
hypotenuse = 102*√2≈144.25 yards
the diagonal ≈144.25 yards
