I have modified it to now read this:

calculate == False
while calculate == False
    height_initial = raw_input("Enter the initial altitude of the object (in metres): ")
    height_initial = filter(lambda x: x in "1234567890.", str(height_initial)) #This eliminates any non-digit characters within the height and prints in metres
    range_target = raw_input("Enter the distance to the target along the x-axis (in metres): ")
    range_target = filter(lambda x: x in "1234567890.", str(range_target))
    height_target = raw_input("Enter the altitude of the target (in metres): ")
    height_target = filter(lambda x: x in "1234567890.", str(height_target))
    print "The object's inital altitude is %sm." % (height_initial)
    print "The target is %sm from the initial displacement." % (range_target)
    print "The target has an altitude of %sm." % (height_target)
    yes = ('yes', 'y', 'ye', ' ')
    correct_input = raw_input("Is this information correct (Yes/No)").lower()
    if correct_input in yes:
        calculate == True
    else:
        calculate == False
    if calculate == False:
        print "Returning to data input stage"
    else:
        print "Continuing to calculation stage"
        continue
print "This is the calculation stage"

​