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<body>Hallo<br />
<br />
The ST_DWithin fuction will only check the 2d distance and not care it the points are far from each other in z direction.<br />
<br />
If you need to also check they are close in z-direction I guess the easiest way is to calculate the 3d distance between the points with Pythagorean theorem. The cleanest maybe is to make a function of it like this:<br />
<br />
<br />
create or replace function pointdistance3d(p1 geometry, p2 geometry)<br />
returns double precision as<br />
$$<br />
select sqrt((st_x($1)-st_x($2))^2 + (st_y($1)-st_y($2))^2 + (st_z($1)-st_z($2))^2);<br />
$$<br />
language 'sql';<br />
<br />
<br />
then to get some speed of it you can use st_dwithin to do a first index-based search. That is as said only a 2d calculation, but if the distance is more than your tolerance in 2d it will be also in 3d.<br />
<br />
I think the most effective way of doing this is to only do the bounding box comparison that is built into st_dwithin and then go straightly to the 3d calculation. That would look something like this if we use the tolerance 0.1 meters (requires based coordinate sytem):<br />
<br />
Select * from table1, table2 where table1.the_geom && ST_Expand(table2.the_geom, 0.1) and<br />
table2.the_geom && ST_Expand(table1.the_geom, 0.1) and pointdistance3d<=0.1;<br />
<br />
Hope that helps<br />
<br />
Nicklas<br />
<br />
<br />
Try:<br />
> ST_DWithin(point1, point2, 0.00001) <br />
><br />
>-F<br />
><br />
>>
<div>2010/5/22 eehab hamzeh <<a>eehab40@hotmail.com</a>><br />
>
>
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Hello <br />
><br />
>I want to check if two points are identical, the points has x,y,z coordinates and they are not exactly the same, i need to check the intersection between them with tolerance value. any direction of how to do that.<br />
><br />
>Thank <br />
><br />
>kind regards<br />
>>
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