I'm trying to plan an April 17 hike on the GR4 from Grasse to Manosque with a view to fly into Nice and leave from Marseille. When I want to check air, bus, train and coach routes I tend to refer to the 'Rome to Rio' site. What I am hoping to find is a site(s) which does the same thing for GR hiking routes in France? For example, to tell me how many kilometers of walking it is on the GR4 from Grasse to Castellane? I can them make a judgement as to how many hiking days to book between flights. If I'm booked to fly out on a certain day I don't want miss it. Does anyone know if such a site exists?