Simon, you could do this as a PostGIS query. To take the polygon case, if you loaded the data into a table in PostGIS called parcel (say), you could run a query something like the following (not guaranteeing this is exactly correct but something along these lines):<div>
<br></div><div>select <a href="http://a.id">a.id</a>, <a href="http://b.id">b.id</a>, </div><div>ST_distance(a.geom, b.geom), </div><div>ST_distance(ST_centroid(a.geom), ST_centroid(b.geom)),</div><div>ST_azimuth(ST_centroid(a.geom), ST_centroid(b.geom))</div>
<div>from parcel a, parcel b<br><br></div><div>This would give you ids, shortest distance, distance between centroids and angle between centroids. There are no doubt others here who can correct my SQL syntax :) !</div><div>
<br></div><div>There is a simple utility to load a shape file into PostGIS.</div><div><br></div><div>Cheers,</div><div> Peter.</div><div><br><div class="gmail_quote">On Thu, Dec 3, 2009 at 3:49 PM, Simon Cropper (Botanicus Australia Pty Ltd) <span dir="ltr"><<a href="mailto:scropper@botanicusaustralia.com.au">scropper@botanicusaustralia.com.au</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div bgcolor="#ffffff" text="#000000">
Hi Everyone,<br>
<br>
My name is Simon and I am an environmental consultant. I use a variety
of open source GIS systems and tools almost every day to analyse flora,
fauna and vegetation data. I am interested in OSGeo both from the
standpoint (or my underlying belief) that software and data should be
free (you know how the mantra goes) and my desire to contribute to a
broader community effort to develop appropriate software for users. I
have been actively using OpenJUMP, Kosmo, OpenEV, EveryDWG and
Sextante. I have tinkered with Ilwis, GRASS, Quantum (various versions)
and a few others I have lost track of. I am currently using
GVSIG+Sextante, which I find very useful and easy to use. I am an old
user of ArcView 3.1+(numerous scripts/extensions).<br>
<br>
I have a common GIS problem but can not find any OSGeo project that has
provided a set of tools to combat it. I need to establish the
distance+angle between various geometries (points, lines, polygons) in
same layer and in different layers. A specific problem I currently have
is finding the minimum distance and angle between 200 odd polygons in
the same layer. Each polygon has a unique id and I want to get a table
with UID_A, UID_B, MINIMUM_DISTANCE, ANGLE. I know that ArcGIS and
ArcView have this functionality, and script exist for old versions of
ArcView, but I am looking for an Open Source alternative.<br>
<br>
Ideally such a tool would create the following data for each geometry
type...<br>
<br>
POINTS -- UID_A, UID_B, DISTANCE, ANGLE<br>
LINES -- UID_A, UID_B, DISTANCE_AT_CLOSEST _POINT<br>
POLYGON -- UID_A, UID_B, MIN_DISTANCE, MAX_DISTANCE,
HAUSDORFF_DISTANCE, CENTROID_DISTANCE, ANGLE_BETWEEN_CENTROIDS<br>
<br>
What I have found already...<br>
<ul>
<li>I have noted that Sextante can create a matrix of distances
between points within the same layer. With rows and column representing
the complete set of points being compared. <br>
</li>
<li>I have also found QGIS has a fTools Plugin that allows you to
"Measure distances between two point layers, and output results as a)
Square distance matrix, b) Linear distance matrix, or c) Summary of
distances." QGIS 2009. <br>
</li>
<li>I suspect that GRASS would provide this functionality but can't
get that package to work on my system (even WinGRASS), so if you point
me here please also point me to a tutorial on getting the thing to work
(this system is not intuitive; My problem has been in establishing a
repository and getting data into it for viewing, let alone analysis; it
failed the age old test that if you can't even get the thing running in
half an hour, the learning curve is going to be way too high to use in
in normal business activities; I have tried - yes following their
instructions - several times, and spent several days reading manuals,
wiki's,etc to no avail).<br>
</li>
</ul>
<big>BUT I can't find any tool</big> that allows me to calculate the
minimum distance between polygons and indicate the direction of the
polygon.<br>
<br>
Anyone out there know of such a tool?<br>
<br>
Note: I am using Windows XP Pro SP3 and store all my GIS data as
shapefiles.<br>
<div>-- <br>
<p>Cheers Simon</p>
<p style="margin-left:36pt">
Simon Cropper <br>
Botanicus Australia Pty Ltd<br>
PO Box 160, Sunshine, Victoria 3020.<br>
P: 9311 5822. M: 041 830 3437.<br>
<a href="mailto:scropper@botanicusaustralia.com.au" target="_blank">mailto:
scropper@botanicusaustralia.com.au</a> <br>
<a href="http://www.botanicusaustralia.com.au" target="_blank">web:
www.botanicusaustralia.com.au</a> <br>
</p>
</div>
</div>
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