[postgis-users] finding whether an object lies in vicinity of another object

[Tom van Tilburg]

Hi Tasneem,

You will have to create a geometry first before you can use postgis 
functions. Just 2 columns with coordinates are not enough (you're very 
close though).
I would recommend to do some reading in the manual, especially here:
http://postgis.refractions.net/documentation/manual-2.0/PostGIS_FAQ.html#id605751

It boils down to adding a column with

	SELECT AddGeometryColumn('', 'yourtable','geom',-1,'POINT',2);

and then filling the column with
     UPDATE yourtable SET geom = ST_SetSrid(ST_MakePoint(xcolumn, 
ycolumn),4326)
     (see: 
http://postgis.refractions.net/documentation/manual-2.0/ST_MakePoint.html)

Besides that: most likely you want to use ST_DWithin, it's supposed to 
be faster than ST_Within.

Cheers,
  Tom

On 8-10-2012 14:40, tasneem dewaswala wrote:
> Hello,
>
> I am developing an application to find whether two cars are in each 
> other communication range or not.
> I have two tables like receiver and transmitter. i would like to know 
> if receiver is in 100 meters range of transmitter or not.
> Since i am using PostgreSQL first time, i donno much about its 
> functions and commands, but i have found that there is ST_Within(), 
> which can be used for my work. I tried but it gives me lot of errors, 
> probably because of data types of my latitude and longitude. they are 
> in two different columns with datatype as double precision.
>
> please tell me what is wrong, and how should i use ST_WITHIN for my 
> work. Or tell me any other way of knowing if two objects are in range 
> of each other.
>
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20121008/f01cfaea/attachment.html>