[GraphHopper] Understanding GraphHopper Instructions

[Matthias Marquardt]

Peter - would you mind, to review my suggestion for an adjustment in the
Instruction calculation? - With this changes I was able to create the
expected TurnByTurn Instructions I am looking forward to receive from
GraphHopper once I am offroad


2014-06-28 16:20 GMT+02:00 Matthias Marquardt <marquardt24 at gmail.com>:

> ... I think I have already found it :-)
>
> com.graphhopper.routing.util.EncodingManager.applyWayTags(...)
>
> right?!
>
>
> 2014-06-28 16:04 GMT+02:00 Matthias Marquardt <marquardt24 at gmail.com>:
>
> Hello,
>>
>> my name is Matthias - 43 year old guy from the Bielefeld area. I want to
>> make use of your offer 'do not hesitate to ask questions' - I am at the
>> begin of a none commercial outdoor project - before I am going into details
>> [what I plan to do, and why I expect that GraphHopper is just the 'right'
>> thing (beside the fact that's pure Java and I am lazy too!)] - I am
>> currently focusing on the instruction list functionality.
>>
>> At the beginning I had difficulties to understand why they are, like they
>> are - when it comes to short trails like this one:
>>
>>
>> http://graphhopper.com/maps/?point=51.271743%2C8.648402&point=51.274045%2C8.646782&vehicle=bike2&elevation=true
>>
>> I am missing at least one (IMHO essential) turn in the resulting
>> instruction list (in the last section of the path (shortly after leaving
>> the woods) - without knowing too much details about the used OSD from that
>> specific area I am even more confused when I move the endpoint to the other
>> path...
>>
>>
>> http://graphhopper.com/maps/?point=51.271743%2C8.648402&point=51.274421%2C8.648252&vehicle=bike2&elevation=true
>>
>> Still only two turns - and the (IMHO essential) instruction is missing -
>> actually my "expectation" would be, that I would get four (or even five)
>> turning instructions for this small route.
>>
>> Lucky enough the GraphHopper sources are available, so I made my way
>> though the calls (while having the code running in my IDE debugger) and
>> realized the root of my "issue" is in the com.graphhopper.routing.Path
>> class - to be more precise in the lines 416, 417 and 418 (in the
>> 'forEveryEdge' code)
>>
>>                     if ((!name.equals(tmpName))
>>                             || (!annotation.equals(tmpAnnotation)))
>>                     {
>>
>> While the graph in the given example has six edges the resulting list of
>> instructions will be so short simply cause the edge objects does not have
>> any names AND no essential differences in their annotations - this even
>> explains instantly, why when switching over from bike to foot, that I get
>> zero turning instructions at all, since the foot encoder does not not make
>> any differences in the annotations...
>>
>> So with other words (moving away from the java object world back to the
>> real world) - the current GraphHopper version give you only instructions,
>> IF there is a significant change between the edges [like street name
>> change, or change from tarmac to gravel] - I do not doubt, that the chosen
>> implementation is the right way by default - a quick test (removing the
>> name & annotation check) showed me that with my hacked code, the
>> instruction list result is finally matching "my expectation".
>>
>> My question right now is, since I have realized, that the extracted data
>> is IMHO the root cause of the issue, in which area of the code I have to
>> dig for the portion, that is responsible for creating the base data from
>> which later the edges are created - since my next attempt would be to give
>> every path that will be extracted from the OSM data a unique name (if not
>> present) - or would that be a silly idea?! [I think I will add a prefix, so
>> that when the name later will be used, it can be detected, that this is
>> just a "internal name" - and that instructions like 'turn left to
>> MyUUIDPrefix_243211' could be avoided']
>>
>> TIA - Matthias
>>
>
>
>
> --
> Matthias Marquardt
> http://about.me/matthiasmarquardt
>
> [FileScout | iMazing | Iconify | TOMPlayer | LittleBrother | GPSLogger II
> | GPSiesConnect]
> http://www.emacberry.com
>  <http://about.me/matthiasmarquardt>
>



-- 
Matthias Marquardt
http://about.me/matthiasmarquardt

[FileScout | iMazing | Iconify | TOMPlayer | LittleBrother | GPSLogger II |
GPSiesConnect]
http://www.emacberry.com
 <http://about.me/matthiasmarquardt>
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