Odd issue with trip calculation

[Pete of Ebor]

Hi, not really a serious issue but something I have just noticed. Our trip next May is a one-way trip from Sowerby Bridge Basin to Portland Basin. Being a one way trip, we won't know where we will start from until a week before, so I thought I would create both options. I first created the trip from Portland Basin to Sowerby Bridge Basin. Using the default values it came out as 36 miles and 6 Furlongs, and would take 34 hours and 30 mins.
I then reversed the trip using the reverse direction arrows on the route editor, and the same trip came out as the same distance (36 miles and 6 furlongs) but only 33 hours 45 min.
I reversed it again and it returned to 34 hrs 30 min.
I Know it's not exactly earth-shatteringly wrong, but I'm just curious as to why. Is it some form of rounding error or does it actually take river flows into account ? Presumably, going downstream on the river sections of the Calder & Hebble might be a little bit quicker than going upstream.. ? Or is it something else ? Just curious really.

[Stephen Atty]

That's quite odd but interesting. I wondered at first if it was anything to do with river navigations and flows but I don't think it is.

I wonder if Nick has any thoughts on it.

[Administrator]

That's exactly what it is!  The flow on the C&H.

If you go to \"preferences -> speeds\" you'll see two boxes for \"Effect of flow\" in mph.  If you set those to zero you'll find you get the exact same time (he says with blithe confidence in his code and without testing it).

[Pete of Ebor]

Wow ! Just tried it and it's right. I didn't realise the coding was that in-depth (forgive the pun !) We don't do many navigable rivers, and I'd never even realised that setting was there. Having said that, we've used canalplan for quite a few years now and always found it really useful and pretty accurate as far as timings go. Thanks so much and keep up the good work.