'[postgis-users] Problem with overlay'

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List: postgis-users
Subject: [postgis-users] Problem with overlay
From: "Jonathan Aguero" <jua130 () psu ! edu>
Date: 2007-06-30 18:05:27
Message-ID: !~!UENERkVCMDkAAQACAAAAAAAAAAAAAAAAABgAAAAAAAAATR1TnoRRqU2OBfkDJYrxesKAAAAQAAAAzzvVbvS4kUWtIS9RHRO6owEAAAAA () psu ! edu
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Listers

I got a multilinestringM shape that I loaded into postgis without problem
(LRS). Then I used the linear referencing functions to create the segments
and curves tables from the tables (BTW, these linear referencing functions
rock!!!!). Now, my problem is that when I tried to join the information on
curves into the segments table using the overlay function, it failed to
detect several curves. Note that both geometries (segments and curves) are
generated from the same base lines (LRS), therefore all curves should
overlay one or more segments. I am guessing I encountered a precision
problem on GEOS but I wonder whether my guess is correct and if there is any
solution (maybe snaptogrid).  

Thanks in Advance for your help

PS:

OS: Windows XP

PGSQL: PostgreSQL 8.2.3 on i686-pc-mingw32, compiled by GCC gcc.exe (GCC)
3.4.2 (mingw-special)

Postgis: 1.2

GEOS: 3.0.0rc4-CAPI-1.3.3

Jonathan Aguero Valverde

Research Assistant and Ph.D. Candidate

Pennsylvania State University

The Pennsylvania Transportation Institute

201 Transportation Research Building

University Park, PA 16802

www.personal.psu.edu/jua130

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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Listers</span></font></p>

I got a multilinestringM shape that I loaded into postgis
without problem (LRS). Then I used the linear referencing functions to create the
segments and curves tables from the tables (BTW, these linear referencing
functions rock!!!!). Now, my problem is that when I tried to join the
information on curves into the segments table using the overlay function, it
failed to detect several curves. Note that both geometries (segments and curves)
are generated from the same base lines (LRS), therefore all curves should
overlay one or more segments. I am guessing I encountered a precision problem
on GEOS but I wonder whether my guess is correct and if there is any solution (maybe
snaptogrid). &nbsp;

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Thanks in Advance for your help</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>PS:</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>OS: Windows XP</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>PGSQL: PostgreSQL 8.2.3 on i686-pc-mingw32, compiled by GCC
gcc.exe (GCC) 3.4.2 (mingw-special)</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Postgis: 1.2</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>GEOS: 3.0.0rc4-CAPI-1.3.3</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>&nbsp;</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>&nbsp;</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Jonathan Aguero Valverde</span></font></p>

Research Assistant and Ph.D. Candidate

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
  font-family:Arial'>Pennsylvania</span></font><font size=2 face=Arial><span
 style='font-size:10.0pt;font-family:Arial'> </span></font><font size=2
  face=Arial><span style='font-size:10.0pt;font-family:Arial'>State</span></font><font
  size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> \
</span></font><font  size=2 face=Arial><span \
style='font-size:10.0pt;font-family:Arial'>University</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The Pennsylvania Transportation Institute</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>201 Transportation Research Building</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
  font-family:Arial'>University Park</span></font><font size=2 face=Arial><span
 style='font-size:10.0pt;font-family:Arial'>, </span></font><font size=2
  face=Arial><span style='font-size:10.0pt;font-family:Arial'>PA</span></font><font
 size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> \
</span></font><font  size=2 face=Arial><span \
style='font-size:10.0pt;font-family:Arial'>16802</span></font></p>

<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><a \
href="www.personal.psu.edu/jua130">www.personal.psu.edu/jua130</a></span></font></p>

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12.0pt'>&nbsp;</span></font></p>

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