Haversine (exp)

function haversine(geoloc:TGeolocation; lat,long:Double):Double;

Retourne la distance entre l'attribut Geolocation et un jeu de coordonnées.

Exemple :

Utilisation d'arguments

//Procedure TestGeolocation;
var sel:TSelector; S:string; stag:string; inst:WFAddress; dd:double; lat,long:double;
begin
  // looks for address in 100 meters range from a point.
  //
  lat := 38.897147;
  long := -77.043934;
  sel := WFAddress.CreateSelector('haversine(geoloc,%2,%3) < %1','',true,[0.1,lat,long]);
 
  foreach inst in  sel.AsCursor do
   begin
     dd := inst.Geoloc.haversine(38.897147,-77.043934);
     showMessage(Format('%s %0.4f',[inst.Address1,dd]));
   end;
end;

Utilisation de constantes

//Procedure TestGeolocation;
var sel:TSelector; S:string; stag:string; inst:WFAddress; dd:double; 
begin
  // looks for address in 100 meters range from a point.
  //
  sel := WFAddress.CreateSelector('haversine(geoloc,38.897147,-77.043934) < %1','',true,[0.1]);
 
  foreach inst in  sel.AsCursor do
   begin
     dd := inst.Geoloc.haversine(38.897147,-77.043934);
     showMessage(Format('%s %0.4f',[inst.Address1,dd]));
   end;
end;

Requête SQL générée par ces exemple:

select t0.* from dbo.WFADDRESS t0
where dbo.udf_haversine(t0.Geoloc_lat,t0.Geoloc_long,38.897147,-77.043934) < 1.000000000000000060E-001
order by t0.oid

Voir aussi:

— Expressions objets (code) — Développement DSM —