[GRASS-user] Finding Nearest Intersection (point) on Road Network

[Moritz Lennert]

On 05/01/09 20:44, Ryan Rosario wrote:
> 
> Moritz Lennert wrote:
>>
>> Thanks for the reply. Sorry for the delay...out of town.
>>
>> On Wed, December 24, 2008 05:55, Ryan R. Rosario wrote:
>>> GRASS simply returns the same point back, since the closest node to A is
>>> A.
>> In grass6.4 you have the dmin option to avoid that.
>>
> 
> That is good to know. Apparently it is not in the tcl/tk GUI.

That is odd, as the GUI should automatically be created from the module 
(and dmin is in 6.4 - just checked). What does v.distance --help give you ?

Are you sure you are using 6.4 ? From when ? The feature was added 
mid-August.

[...]


>> Note that currently the v.net.* modules
>> in GRASS do not work very well, and hardly at all once the network becomes
>> too big. Rewriting these modules to be more scalable and reliable would be
>> a nice Google Summer of Code project for next year.
>>
> 
> That would be excellent. Now that I know this, I might take a look at the
> code, as what I am trying to do relates to my dissertation. 

As Markus said, this seems to be mostly related to the cache bug 
(http://trac.osgeo.org/grass/ticket/224), but there have also been 
discussions about underlying algorithms (see the dglib vs dgtables in 
the threads referenced in the bug report).

I guess the best thing would be to fix the cache bug to then finally be 
able to test the networking modules in more real life heavyload 
applications than possible now. I know of quite a few people who would 
willingly switch over to GRASS if the networking stuff was top of the line.

But it might be interesting to look at some recent literature on network 
/graph issues. I'm no expert, but have the feeling that a lot has been 
going on there...

Moritz