Distance Between IP to Nose?

Hi all

 I have placed a crossover between 2 parallel tracks (1432 gauge, 1970 interval).

 Both crossover units are standard CV 1 in 9.25.

 The design distance between the IP and nose should be 0.148m.

 However when I measure the distance between the IP and Nose I get 0.125m measured along the straight and 0.126m measured along the diagonal.

 The question is why is it 0.125m it should be 0.148m – what am I missing?

 Can someone help?

Thanks