Why waypoint distances are not equal?

[Aceostrat]

Hi everyone, we are now flying mostly on PBN routes. So I am just wondering what determines the different distances between waypoints and why they are not just equally apart? Really appreciate it.

[rudestuff]

I think they probably would be if the system were designed from scratch for PBN use. The problem is most routes were originally designed around ground based facilities like VORs and NDBs* so the system evolved by adding more and more routes over time. You will find some parts of the world where airways are parallel, equally spaced and with regularly spaced way points. But then you just have unnecessarily long routes covering too many legs pages.

*whatever those are

[cris95123]

FMS distances are always shorter than chart distances due to FLY BY procedure..........FMS distances are computed once on track (ARINC 424 coding)
https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/962x753/flyby_a30444e78ea49cad57d0d0c7c79836600ee311c6.png
you are on track