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.
Is it desgined to be used that way ?
Am I missing something ?
Thanks
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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Hi,
Le 17/11/2014 23:35, Stephen Woodbridge a écrit :
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, BDThere 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
Yes. But, with a closer look, my data are still fine.
Consider the following simple case of two segments crossing on (5,5) :
create table network (id int, the_geom geometry(linestring) );
insert into network values (1, 'linestring(0 0, 10 10)'::geometry);
insert into network values (2, 'linestring(2 0, 8 10)'::geometry);
select pgr_nodeNetwork('network', 0.001);
The "network_noded" table then contains 4 geometries :
LINESTRING(0 0,1 1) <-- the first segment split on what seems to be the
projection of the starting point of the second segment (?)
LINESTRING(1 1,9 9) <-- split on the projection of the ending point of
the second segment
LINESTRING(9 9,10 10)
LINESTRING(2 0,8 10) <-- the original second segment
Is it what is expected ?
I expected to find the two geometries split on the (5,5) point ...
PS: I am using pgrouting 2.0.0
On 11/18/2014 3:31 PM, Hugo Mercier wrote:
Hi,
Le 17/11/2014 23:35, Stephen Woodbridge a écrit :
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, BDThere 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
Yes. But, with a closer look, my data are still fine.
Consider the following simple case of two segments crossing on (5,5) :
create table network (id int, the_geom geometry(linestring) );
insert into network values (1, 'linestring(0 0, 10 10)'::geometry);
insert into network values (2, 'linestring(2 0, 8 10)'::geometry);
select pgr_nodeNetwork('network', 0.001);The "network_noded" table then contains 4 geometries :
LINESTRING(0 0,1 1) <-- the first segment split on what seems to be the
projection of the starting point of the second segment (?)
LINESTRING(1 1,9 9) <-- split on the projection of the ending point of
the second segment
LINESTRING(9 9,10 10)
LINESTRING(2 0,8 10) <-- the original second segmentIs it what is expected ?
No I do not think that was the intention. Please open a ticket and document this, so it can get fixed.
I expected to find the two geometries split on the (5,5) point ...
This is the intended behavior.
Thanks,
-Steve
PS: I am using pgrouting 2.0.0
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