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<div>Dear PostGis Users,</div>
<div> </div>
<div>we are using PostgreSQL / PostGIS very intensively - at the moment in combination with PG-Routing.</div>
<div>Because we are routing on areas, we create somthing like a network on them and intersect this netzwork with some area - properties (e.g. vegetation).</div>
<div> </div>
<div>While doing this, a very strange behaviour occured: intersection of two lines created a point, which is relative far away from one line. Here the simplified sql - statment:</div>
<div> </div>
<div>select asText(intersection(b.g, a.g)) as intersection, </div>
<div>distance (a.g, intersection(b.g, a.g)) as distance</div>
<div>from </div>
<div>(select '01020000000200000050E8303FC2E85141B017CFC05A825541000000E0C0E85141000000205C825541'::geometry as g) a,</div>
<div>(select 'LINESTRING(4694792.35840419 5638508.89950758,4694793.20840419 5638506.34950758)'::geometry as g) b</div>
<div> </div>
<div>-> so the distance of point and first line is 0.88 (meters)</div>
<div> </div>
<div>when I use asText for the first Line:</div>
<div> </div>
<div>select asText(intersection(b.g, a.g)) as intersection, </div>
<div>distance (a.g, intersection(b.g, a.g)) as distance</div>
<div>from </div>
<div>(select asText('01020000000200000050E8303FC2E85141B017CFC05A825541000000E0C0E85141000000205C825541'::geometry) as g) a,</div>
<div>(select 'LINESTRING(4694792.35840419 5638508.89950758,4694793.20840419 5638506.34950758)'::geometry as g) b</div>
<div> </div>
<div>-> the distance reduces to a very little value (xe-10) - with this I have no problem, because I use some little tollerance - but 0.88 is too much in my case.</div>
<div> </div>
<div>As a workaround I use allways asText at the moment. </div>
<div>Our PostGIS fullVerion is </div>
<div>"POSTGIS="1.3.2" GEOS="3.0.0rc4-CAPI-1.3.3" PROJ="Rel. 4.5.0, 22 Oct 2006" USE_STATS"</div>
<div>on "PostgreSQL 8.2.4 on i686-pc-mingw32, compiled by GCC gcc.exe (GCC) 3.4.2 (mingw-special)"</div>
<div> </div>
<div>By the way - the same Statment in </div>
<div>"POSTGIS="1.2.0" GEOS="2.2.3-CAPI-1.1.1" PROJ="Rel. 4.5.0, 22 Oct 2006" USE_STATS"</div>
<div>on "PostgreSQL 8.2.0 on i686-pc-mingw32, compiled by GCC gcc.exe (GCC) 3.4.2 (mingw-special)"</div>
<div>creates a point with a small distance (but >0) in both cases</div>
<div> </div>
<div> </div>
<div>Greetings </div>
<div> </div>
<div>Thomas and Rene</div>
<div> </div>
<div> </div>
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