[pgrouting-users] pgr_nodeNetwork ?

[Stephen Woodbridge]

On 11/17/2014 3:17 PM, Hugo Mercier wrote:
> Hi all,
>
> I am trying to use pgr_nodeNetwork to split crossing lines (both
> X-shaped and T-shaped).
> It seems to add way more new nodes than needed. Lines are sometimes
> split right in the middle where there is no reason for that (no
> intersection).
> Playing with the tolerance argument does not seem to solve the issue.

Tolerance needs to be set in the units of your data, ie: if you data is 
in WGS84 decimal degrees then you need a tolerance like 0.000001 But if 
you data is in meters then a tolerance of 1.0 is probably fine. Of 
course this all depends on your data.

If you have lines like

A---------C-B---------D

where the original segments are AB and CD then you will get new segments 
AC, CB, BD

There are lots of cases that look fine when you view the data, but are 
not so good when we analyze the data. Also if you tolerance is wacky 
then there is not telling what might happen.

-Steve

> Is it desgined to be used that way ?
> Am I missing something ?
>
> Thanks
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