Index: /issm/trunk-jpl/src/m/interp/interp.py
===================================================================
--- /issm/trunk-jpl/src/m/interp/interp.py	(revision 17597)
+++ /issm/trunk-jpl/src/m/interp/interp.py	(revision 17598)
@@ -36,12 +36,31 @@
 	assert len(kwargs)==0, 'error, unexpected or misspelled kwargs'
 
-	points=npy.array([x,y]).T
+	# create sub-vectors that just cover the limits of xi and yi
+	dx=x[1]-x[0]
+	dy=y[1]-y[0]
+	xlim=[min(xi)-dx,max(xi)+dx]
+	ylim=[min(yi)-dy,max(yi)+dy]
+	xflag=npy.logical_and(x>xlim[0],x<xlim[1])
+	yflag=npy.logical_and(y>ylim[0],y<ylim[1])
+	bothind=npy.nonzero(npy.logical_and(xflag,yflag))
+	subdata=data[bothind]
+	subx=x[bothind]
+	suby=y[bothind]
+	points=npy.array([subx,suby]).T
+
+	# mask out any nan's in the data and corresponding coordinate points
+	mask=npy.isnan(subdata)
+	ind=npy.nonzero(mask)[0]
+	if len(ind):
+		print "WARNING: input data grid contains nan values. Spline interpolation may be questionable."
+	subdata=npy.delete(subdata,ind)
+	points=npy.delete(points,ind,axis=0)
 
 	if maxiter:
-		curvy=CloughTocher2DInterpolator(points,data,tol,maxiter=maxiter)
+		spline=CloughTocher2DInterpolator(points,subdata,tol,maxiter=maxiter)
 	else:
-		curvy=CloughTocher2DInterpolator(points,data,tol)
+		spline=CloughTocher2DInterpolator(points,subdata,tol)
 
-	interpdata=curvy(xi,yi)
+	interpdata=spline(xi,yi)
 
 	return interpdata
@@ -99,12 +118,12 @@
 	mask=npy.isnan(flatsubdata)
 	ind=npy.nonzero(mask)[0]
-	if float(len(ind))/float(len(flatsubdata)) > 0.1:
-		print "WARNING: over 10% of data grid contains nan values. Spline interpolation may be questionable."
+	if len(ind):
+		print "WARNING: input data grid contains nan values. Spline interpolation may be questionable."
 	flatsubdata=npy.delete(flatsubdata,ind)
 	points=npy.delete(points,ind,axis=0)
 
 	# create spline and index spline at mesh points
-	spl=CloughTocher2DInterpolator(points,flatsubdata)
-	interpdata=spl(xi,yi)
+	spline=CloughTocher2DInterpolator(points,flatsubdata)
+	interpdata=spline(xi,yi)
 
 	return interpdata