Road speeds

[mari.ma...@gmail.com]

Hi!

All roads in my dataset have maxspeed tag set. So I assumed, that all speed data

is taken from that tag and speeds in speed profile are not taken into account at all.

For testing purposes, I set

maxSpeed=1000

defaultCitySpeed=1000

averageSpeed=1000

for some road types. It seems, that speed profile data ise used instead of maxspeed

tag.

So my question is - how are maxspeed tag and maxSpeed, averageSpeed

and defaultCitySpeed values in speed profile used?

Second question - how does road priority (i.e. highway.0.priority=4) affect routing 

result? From old-school point of view, algorithm tries to find quickest way, based

on ride time for edge (calculated from speed and road length). For priorities,

speeds were multiplied by constant (eg. 1.5 for higher and 0.5 for lower priorities).

Best regards

[Christian Vetter]

Hi,

Regarding your first question:

Speed calculation in MoNav is as follows:

1. Determine "Max Speed":
- if given in the map use that one, but limit to maxSpeed ( e.g.
Pedestrian could be limited to 6kmh )
- otherwise derive from road type and "in-city" flag, either
defaultCitySpeed or maxSpeed
2. Compute average speed as percentage of "Max Speed", depending on road type
3. Apply modifiers

So in your case, you would use the max_speed from the map ( it is
smaller than 1000 ), but compute the average speed as 1000% of the max
speed, since it is given in percents.
Could you try setting averageSpeed to 100 ( or leave it on the default
values ) if you want to test whether your speeds are used?

Also, the maxspeed tag needs to be well formed, i.e., it needs to be a
floating point number followed by one of the following strings:
"kmh"
" kmh"
"km/h"
" km/h"
"kph"
" kph"
"mph"
" mph"
"" -> will be mapped to kmh

Regarding the second question:
The priority is only used to calculate turn costs, e.g. if you cross a
road of lower priority it will take longer.

The routing algorithm itself doesn't try to "cheat", by preferring
higher priority roads even if they are slower ( typical A* in
commercial application will do that, gives you a speed boost but not
the optimal result ), since it is capable of computing the optimal
route without any performance loss.
You could say, that MoNav optimizes for time ( length / average speed
+ turn cost ) only, so you will always get the fastest route possible.

I hope that answers your questions *G*

Best regards,

Christian Vetter

[mari.ma...@gmail.com]

Hi Christian,

thanks for thorough explanation! Everything is clear now, expect for one detail:

>  Determine "Max Speed": 

> - if given in the map use that one, but limit to maxSpeed ( e.g. Pedestrian could be limited to 6kmh )  

What is that "maxSpeed" - is it max speed for given road type from speed profile, or some configuration 

variable, that I haven't discovered yet?

I'm making really good progress with MoNav now, and I would appreciate explanation on following

.spp variables:

otherLeftPenalty

otherRightPenalty

otherStraightPenalty

otherLeftEqual

otherRightEqual

otherStraightEqual

leftPenalty

rightPenalty

Best regards

[Christian Vetter]

Hi,

"maxSpeed" is the speed from the profile. This way you can create a
profile for "vehicles" ( bicycle, pedestrian ), that cannot exceed a
certain speed limit.

Regarding the penalty values: Their are used to compute turn costs,
otherXXX are applied of you have a junction with other streets of
lower priority, and you turn left, right, or go straight.
otherXXXEqual are applied if you have a junction with other streets of
equal priority. leftPenalty/rightPenalty are base penalties for
turning left / right.
However, these turn costs are currently not being used by the routing
engine, mainly for storage space reasons ( would increase size of the
routing graph by a factor of 2 or so ), so you can safely ignore them
for now.

Best regards,

Christian

[mari.ma...@gmail.com]

Thanks again!