[postgis-users] Spatio-Temporal Function

[Jorge Gustavo Rocha]

Hi,

Qua, 2011-03-02 às 21:55 -0800, Nick raj escreveu:
> Hi,
> I am writing some spatio-temporal function in postgis.
> Like, ST_Enters( obj_geom, boundary_geom, time t1,time t2)
> i.e. Does vehicle enters in ABC area between time t1 to t2?
> 
> For example, select ST_Enters ( obj_geom, (select boundary_geom from
> boundary), '25/2/2011 12:23:32','26/2/2011') from vehicledata where
> vehicleid= 'XYZ';
> Vehicledata is a table consist of more than 10,000 object location geometry
> named obj_geom.
> 
> On query execution, it take one object geometry at every execution of
> ST_Enters and compare with boundary area. But this doesn't provide proper
> output because it is continous function of time i.e. Enters is made up of
> Disjoint -> Touches -> Inside.First, check for disjoint, if it is true at
> t1, then check for touches at t2 then check for inside at t3, provided
> t1<t2<t3.
> So, for creating this function, i require all the object's geometry before
> it go inside the function. So that it can call only once.
> 
> My first problem is that
> create or replace function ST_Enters(????, geometry,timestamp,timestamp)
> returns boolean ............
> Which kind of data type to be used because i have to catch more than 10000
> rows?
> So, Can anyone tell me which data type can be used to catch this?
> 

You can use the boolean function within another select statement. The
select statement will return the 10k rows for which or function is true.

> Second question is that,
> How to use this function in SQL in continuous manner??
> 

Use a trigger. When new data about the vehicle gets in, you do
something.

> Hope am i clear.
> 
> Thanks in advance

I hope that's help you. Regards,

Jorge

-- 
Jorge Gustavo Rocha
Departamento de Informática
Universidade do Minho
4710-057 Braga
Tel: 253604430 (Geral), 253604479 (Gabinete)
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