[postgis-users] Create circles using a formula

vikashvikky vikashtalanki at gmail.com
Thu Jun 2 08:31:58 PDT 2011


Hi Brent,

   I am really thankful for your reply. The equation I am to use for
calculating radius is 
       radius=(lambda/4*pi)*sqrt((Pt*Gt*Gr)/Pr)

My towers table contains the following columns
tid,lat,lon,lambda,Pt,Gt,Gr,Pr

so as you said the query should be

CREATE VIEW circles AS SELECT tower_id, ST_BUFFER( ST_Transform( ST_SetSRID(
ST_MakePoint(lon,lat), 4326), 900913, (lambda/4*pi)*sqrt((Pt*Gt*Gr)/Pr) ) AS
tower_circle FROM towers

Now for geoserver to generate the circles , creating the postgis store with
table data as layer is enough I guess. Am I going in a right way?


pcreso wrote:
> 
> I'm not conversant with geoserver but have used mapserver to do this sort
> of thing often enough.
> 
> I assume your data is in PostGIS, which means your mapserver DATA
> statement can be an embedded SQL query or a PostGIS view.
> 
> You can create a view on your table, along the lines of:
> 
> create view v_table 
> as select *, buffer(setsrid(makepoint(lon, lat),4326),<formula to
> calculate radius>) as geom
> from table;
> 
> (assuming you want the output data in EPSG:4326)
> 
> or you can set up your process to build the geometry in a physical table
> doing much the same thing, perhaps as an update or insert trigger?
> 
> Use this view, or table as the "table" you provide the WFS service from, &
> the geometries you are providing will be suitably sized circles.
> 
> Note this assumes a constant signal strength unchanged by topography,
> which is very simplistic.
> 
> Tools like GRASS allow you to apply a terrain model to the sites & carry
> out a line-of-sight analysis to generate more accurate polygons descibing
> the expected coverage from a tower.
> 
> If you are displaying thousands of features, you might find WMS with
> srever side rendering gives a better response time than WFS. Geoserver can
> provide both WMS & WFS services, but I think mapserver has some advantages
> in the WMS arena.
> 
> HTH,
> 
>   Brent Wood
>                                  
>  
> On 02/06/2011, at 3:55 AM, vikashvikky wrote:
> 
>> 
>> Hi,
>> 
>> I am doing a project for a telecom company. I have to render circles on
>> the
>> map(assuming the center of the circle as tower and circle as the area
>> covered by that signal), I am using base layers as Google Maps,Yahoo
>> maps(Spherical Mercator) So I have used CreateGeodesicPolygon()
>> successfully
>> to create circles by reading the values from DB.
>> 
>> Now Since I have to render lot of circles, it made me switch to
>> geoserver.
>> Since the data is being provided by telecom company , they provide
>> Lat,Lon,Gt,Gr,Pt,Pr,lambda(I think their meaning is irrelevant here)
>> values.
>> These values are stored in the database as they are. Now should use a
>> equation(FRIIS transmission equation) and substitute each row(of a tower)
>> values to find the distance covered by the tower.Then I have to create
>> circles with that distance(considered as radius) and lon/lat and render
>> them
>> on map using geoserver.
>> 
>> Please suggest me any ideas of how to carry on this task.... I wud be
>> thankful to your guidance
>> -- 
>> View this message in context:
>> http://old.nabble.com/Create-circles-using-a-formula-tp31752667p31752667.html
>> Sent from the PostGIS - User mailing list archive at Nabble.com.
>> 
>> _______________________________________________
>> postgis-users mailing list
>> postgis-users at postgis.refractions.net
>> http://postgis.refractions.net/mailman/listinfo/postgis-users
> 
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> 
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
> 
> 

-- 
View this message in context: http://old.nabble.com/Create-circles-using-a-formula-tp31752667p31758593.html
Sent from the PostGIS - User mailing list archive at Nabble.com.




More information about the postgis-users mailing list