<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">Hi Rob,<br>
<br>
Points in a regular interval have always been a pain to create in
postgis. I hope someone will write a decent linear_reference code
for this some time soon.<br>
<br>
Here's a way to do it:<br>
<br>
1) make a line out of your points (ST_SetSrid(ST_MakeLine(pointa,
pointb), 27700))<br>
2) add an M value to your line (ST_AddMeasure(geom, start, end))<br>
3) generate_series of intervals
generate_series(0,floor(ST_Length(geom)/25.0)) < please check
how to deal with that last segment smaller than 25 meter! <br>
4) now you know how many points you need in every line you can use
(ST_Line_Interpolate_Point(geom, (N*25)/St_Length(geom))<br>
when N being the numbers you got from generate series in 3).<br>
<br>
Make sure not to put dimensional restrictions to your tables since
ST_AddMeasure will want to add that extra M dimension.<br>
<br>
Good luck!<br>
Tom<br>
<br>
On 25-7-2012 12:50, uk52rob wrote:<br>
</div>
<blockquote
cite="mid:1343213438.99947.YahooMailNeo@web29906.mail.ird.yahoo.com"
type="cite">
<div style="color:#000; background-color:#fff; font-family:times
new roman, new york, times, serif;font-size:12pt">
<div style="font-family: 'times new roman', 'new york', times,
serif; font-size: 12pt; ">Hi,</div>
<div style="font-family: 'times new roman', 'new york', times,
serif; font-size: 12pt; "><br>
</div>
<div style="font-family: 'times new roman', 'new york', times,
serif; font-size: 12pt; ">I have two point geometry tables,
with which I need to compare a single point from the left
table to all points in the right table.</div>
<div style="font-family: 'times new roman', 'new york', times,
serif; font-size: 12pt; "><br>
</div>
<div><font face="times new roman, new york, times, serif"
size="3">I need to extract X and Y co-ordinates (EPSG: 27700
OSGB36/British National Grid) every 25m along a </font><font
face="times new roman, new york, times, serif">fictitious</font><font
face="times new roman, new york, times, serif" size="3"> line
between the points in order to build a 'profile' of the land
from a database containing height data.</font></div>
<div><font face="times new roman, new york, times, serif"
size="3"><br>
</font></div>
<div><font face="times new roman, new york, times, serif">Does
anyone have any 'best practise' or experience with this sort
of project?</font></div>
<div><br>
</div>
<div><font face="times new roman, new york, times, serif">Many
thanks,</font></div>
<div><font face="times new roman, new york, times, serif"><br>
</font></div>
<div><font face="times new roman, new york, times, serif">Rob</font></div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
postgis-users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:postgis-users@postgis.refractions.net">postgis-users@postgis.refractions.net</a>
<a class="moz-txt-link-freetext" href="http://postgis.refractions.net/mailman/listinfo/postgis-users">http://postgis.refractions.net/mailman/listinfo/postgis-users</a>
</pre>
</blockquote>
<br>
</body>
</html>