[postgis-users] Newbie Question

Paul Ramsey pramsey at cleverelephant.ca
Tue Aug 5 12:46:14 PDT 2008

Well, that's the opposite of the usual point-in-polygon use case
(given an existing set of polygons and a point input, tell me what
polygons it falls within), but it's equally tractable.

You need an input interface, and that will be the hardest part of your
task. You can do something in Google Maps, if you like, then stuff the
geometry down into a script (php, asp, whatever) that in turn
inscribes it into a SQL statement ala:

select points.id, points.name from points where
st_contains('POLYGON(....)', points.geometry);

Where the 'POLYGON(...)' is constructed by your script from your user
interface input.



On Tue, Aug 5, 2008 at 12:24 PM, Adam Vande More <adam at imedmobility.com> wrote:
> Hello,
> Perhaps my questions were addressed earlier or in some documentation I
> missed. If so, I apologize in advance as I am completely new to GIS and
> PostGIS.  Judging from the documentation I have read, my needs are extremely
> simple vs PostGIS capabilities however I am unsure if the functionality of
> what I want actually exists.
> I deal with areas in the US, territories that are regional in nature but not
> bounded by common things eg state lines, water ways, counties, etc.  They
> are irregular shapes of varying land area.  I also have sets of latitude and
> longitude points.  I would like some type of system where I enter in a
> perimeter of  territories, and find out whether a particular latitude and
> longitude point lies within that perimeter.
> My understanding of this is that I would need to either manually create a
> GML type file with the perimeters in it, or use some type of map authoring
> software to accomplish this goal.  Are my understandings correct and if so
> is there a recommendation for a particular piece of software which can
> fulfill this?
> Also, are the libraries/functions available for determining whether a point
> is in a perimeter?
> Much appreciated,
> --
> Adam Vandemore
> Systems Administrator
> IMED Mobility
> (605) 498-1610
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