[Routing] OpenGPScout

Marcus Wolschon Marcus at Wolschon.biz
Mon Nov 19 05:48:33 GMT 2007


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Andreas Leupin schrieb:
> Hello all,
> I have just renewed my webpage on www.leupinfo.ch/OpenGPScout concerning
> the Open Source Project "OpenGPScout" (Translation of most of the page
> to english, new pdf-files about the concepts).
> I would be interested especially in your opinions about the main
> pdf-file and the concepts roughly described there...

Hello Andreas,

I had a look at the data-format you described.
> 
> a) road-segments (minimum data - additional data to be stored in other files)
> 
> - node reference at the "beginning" of the segment ("0"-end):   3 bytes (2 bytes actual node reference, 1 byte for the relativ definition of the tile, on which the node is)

How do you number your tiles that 1 byte is enough to reference a tile?
Are 2 bytes enough to reference a node? How do you encode them?
(There are way more then 2^16 nodes in OSM so directly storing their id
is no option.)

> - node reference at the "end" of the segment ("1"-end):   3 bytes (2 bytes actual node reference, 1 byte for the relativ definition of the tile, on which the node is)
> - Definition of the position of the segment within the nodes: 1 byte (this information is used for a faster execution of the routing algorithm)
> - velocity- and road category: 1 byte ( 4 bites respectively)
> - length or driving time for the segment: 1.5 bytes (resolution appr. 5m or 5 s, to be discussed)

Why are you storing these values? Do you use a condensed road-network
with all nodes that are not end-nodes or intersections removed?

> - allowed direction, driving restrictions, suitable vehicle categories etc.: 1.5 bytes
> - reserved for additional informations: 1 Byte
> 
> 11 bytes in total per segment (fixed length)
> 
> 
> b) nodes (minimum data), 
> 
> fixed length:
> - number of incoming/outgoing road segments: 1 byte (3 bits for the number of segments (maximum of 8), 5 bits for the type of node (e.g. turn-about etc.))
> - coordinates of the node: 3 bytes (together with the tile reference the position is defined to about  2.5 m)

How do you encode your coordinates?

> - Adjacent end of the road segments: 1 byte (1 bit per segment, 0 = "0"-end, 1 = "1"-end)
> 
> variable length:
> - reference to a incoming/outgoing segment: 2 bytes per segment
> - Which other segments can be reached from the actual segment:  1 byte per incoming/outgoing segment  (used for coding turn-restrictions etc.)
> - Definition of the tile on which the segment is mainly located: 1 byte per 2 incoming/outgoing segments (??)



Marcus
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