Index: /issm/trunk-jpl/src/c/Container/Observations.cpp
===================================================================
--- /issm/trunk-jpl/src/c/Container/Observations.cpp	(revision 14240)
+++ /issm/trunk-jpl/src/c/Container/Observations.cpp	(revision 14241)
@@ -129,14 +129,16 @@
 	Observation *observation  = NULL;
 
+	/*If radius is not provided or is 0, return all observations*/
+	if(radius==0) radius=this->quadtree->root->length;
+
 	/*First, find closest point in Quadtree (fast but might not be the true closest obs)*/
 	this->quadtree->ClosestObs(&index,x_interp,y_interp);
-	_assert_(index>=0);
-	observation=dynamic_cast<Observation*>(this->GetObjectByOffset(index));
-	hmin = sqrt((observation->x-x_interp)*(observation->x-x_interp) + (observation->y-y_interp)*(observation->y-y_interp));
+	if(index>=0){
+		observation=dynamic_cast<Observation*>(this->GetObjectByOffset(index));
+		hmin = sqrt((observation->x-x_interp)*(observation->x-x_interp) + (observation->y-y_interp)*(observation->y-y_interp));
+		if(hmin<radius) radius=hmin;
+	}
 
 	/*Compute radius square*/
-	if(radius==0 || hmin<radius){
-		radius=hmin;
-	}
 	radius2 = radius*radius;