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<p class=MsoNormal><span style='color:#1F497D'>Regina,<o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>You’re simply an
angel! Thank you!<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Just one question:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>The expand(rc.agg_geometry,
0.5) uses *<b>degrees</b>*, right?<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>All the best,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'>Pedro.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'>
postgis-users-bounces@postgis.refractions.net
[mailto:postgis-users-bounces@postgis.refractions.net] <b>On Behalf Of </b>Obe,
Regina<br>
<b>Sent:</b> segunda-feira, 2 de Abril de 2007 13:43<br>
<b>To:</b> PostGIS Users Discussion<br>
<b>Subject:</b> RE: [postgis-users] 10 closest units<o:p></o:p></span></p>
</div>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>I'm not sure how slow this would be depending on how many line
segments you have by name, but it seems the most speedy to write.
Basically I think you want to collect all your roads of N17 into a single
geometry so that you can then apply a single distance check call.</span><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:blue'>So something like</span><span style='font-size:12.0pt;font-family:
"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'> <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:blue'>select u.friendly_name,
distance(transform(u.curr_location, 32628), <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:blue'>transform(rc.agg_geometry,32628))
as thedistance <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:blue'>from (SELECT
collect(r.geometry) as agg_geometry FROM pt_mainland_roads r WHERE r.name =
'N17') rc, units as u <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:blue'>where
rc.agg_geometry && u.curr_location order by thedistance LIMIT 10;</span><o:p></o:p></p>
<p class=MsoNormal> <o:p></o:p></p>
<p class=MsoNormal><span lang=EN-US style='color:blue'>If you have some units
that are not in the bounding box of a road that would be in the top 10, then
you may want to change your where clause to</span><span lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal> <span lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:blue'>expand(rc.agg_geometry,
<somevalue>)&& u.curr_location </span><span lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal> <span lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:blue'>Hope that helps,</span><span
lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='color:blue'>Regina</span><span
lang=EN-US><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p>
<div class=MsoNormal align=center style='text-align:center'><span lang=EN-US
style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<hr size=2 width="100%" align=center>
</span></div>
<p class=MsoNormal style='margin-bottom:12.0pt'><b><span lang=EN-US
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
postgis-users-bounces@postgis.refractions.net [mailto:postgis-users-bounces@postgis.refractions.net]
<b>On Behalf Of </b>Pedro Doria Meunier<br>
<b>Sent:</b> Sunday, April 01, 2007 9:50 PM<br>
<b>To:</b> 'PostGIS Users Discussion'<br>
<b>Subject:</b> [postgis-users] 10 closest units<br>
<b>Importance:</b> High</span><span lang=EN-US style='font-size:12.0pt;
font-family:"Times New Roman","serif"'><o:p></o:p></span></p>
<p class=MsoNormal>Hi All,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=EN-US>@Regina:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Remember you helped me with the 10 closest
units to a given point? This was it:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>(original layers srid==4326 – I want *<b>meters</b>*
so the transform at play)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>SELECT u.id, u.friendly_name,
u.curr_location, t.oid, distance(transform(u.curr_location,32628), transform(t.geometry,
32628)) AS thedistance, u.mobile FROM units AS u, (SELECT roads.oid,
roads.geometry FROM roads WHERE name=’N17’ LIMIT 1) AS t <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>ORDER BY thedistance LIMIT 10;<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>(this query returns the 1<sup>st</sup>
found line segment labelled ‘N17’ which is 68Kms away when the unit is actually
1.8 meters away from the closest line segment of the same label)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>@All<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>This actually returns the FIRST occurrence
of ‘N17’ (the sample).<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>This is *<b>NOT</b>* necessarily the
closest road to the unit’s current location.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I’ve melted half-a-dozen neurons (mainly
due to tiredness at the time of this writing :] )trying to figure out how can I
implement the distance bit in the sub-query…<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Given example for ONE unit:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>select u.friendly_name,
distance(transform(u.curr_location, 32628), <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>transform(geometry,32628)) as thedistance <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>from pt_mainland_roads as r, units as u <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>where name='N17' AND u.curr_location
&& r.geometry order by thedistance LIMIT 1;<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>(this returns the correct result)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>So to summarize things:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>I need help with a query that returns the *<b>FIRST
TEN</b>* units to the *<b>closest given</b>* road. <o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>(Keep in mind that multiple line segments
with the same name exist – I need the closest)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Will try again tomorrow with a clear head
but in the meantime:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Any help would be most appreciated!<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Best regards,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US>Pedro Doria Meunier.<o:p></o:p></span></p>
<div class=MsoNormal align=center style='text-align:center'><span
style='font-size:12.0pt;font-family:"Times New Roman","serif"'>
<hr size=1 width="100%" align=center>
</span></div>
<p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p> </o:p></span></p>
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