[mkgmap-dev] RFC: Consider heightmeters for routing

Mon Apr 6 22:39:55 BST 2009

Mark Burton schrieb:
> Hi Johann,
>
>   
>> So my idea is, to virutally lengthen the roads by the height distance. 
>> This is, if a road has 1km and goes straight then it gets an entry of 1 
>> km in the routing data.. If another road has a length of 1km and a 
>> height difference of 10m, then it gets a length entry of 1.1km. And a 
>> really hilly road with a length of 1km and a height of 100m will get an 
>> entry of 2km.
>> In other words, I would add a percentage of the height to the lenght. 
>> This should made the etrex choose the flater roads.
>>     
>
> What happens when you go downhill, does it make the roads shorter?
>   
No, it doesn't matter, which direction the road goes. It has an height 
difference an gots therefore an penalty.

See the following example:

Start at height 500m
Destination at height 520m

Maybe there are four alternatives, how I can get to the destination

1. +20m
2. +100m, -80m
3. -80m, +100m
4. +30m, -15m, +5m

All height differences get a positive penalty, no matter which 
direction. So the route with the least 'up and down' gets the least 
penalty and should be prefered. If I would consider the direction (which 
is impossible at gmapsupp creation time) then the resulting penalty 
would always sum up to the real height difference and there will be no 
difference.

> Personally, I like the hills when I am cycling so I don't think I would
> use such a feature.
>
>   
In general I agree with you. I like the hills too. For my recreation 
cycling I choose the ways, which looks best to me at the moment, not the 
ones which tells my etrex me to take. :-)

But sometimes I do really long rides (>140km), and then I don't want to 
waste my condition on some hilly routes, if I can reach the destination 
on a flat alternative, maybe alongside a river.

I expect, for the 'short range' routing there will be not much effect, 
as there are to less alternatives to choose from. But on the 'long 
range' routing it may be the difference between a route over hilly 
region or alongside a river.

As I have said in my first mail, this is only a idea, how it could be 
work. I have not written a single line code for this, and as the summer 
is comming, I think I will go more cycling than sitting in front of my 
computer. :-)

Greetings
Johann